the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Nov 2021
The distribution of phosphorus from recycled fertilizers to different soil fractions determines the phosphorus availability in soil
Abstract. Recycling of agricultural wastes to reduce mineral fertilizer input, in particular phosphorous (P), plays crucial role in sustainable agriculture production. Understanding the transformation of phosphorous (P) fractions and their bioavailability following soil application of different renewable P-contained fertilizers is very important for improving P use efficiency and reducing environmental risks. In this study, the effects of mineral P-fertilizer superphosphate and recycled P-fertilizers, i.e., poultry manure, cattle manure, maize straw and cattle bone meal, on their distribution to different soil P fractions, their transformation and the availability of soil P were determined by soil P sequential fractionation and 31P solution nuclear magnetic resonance (NMR). The results showed that addition of mineral P fertilizer, poultry manure and cattle manure increased P fixation in a red soil more than that in a fluvo-aquic soil. In both fluvo-aquic and red soils, cattle manure out-performed all other recycled P sources used in improving soil P availability. The concentration of Olsen-P in fluvo-aquic and red soils supplemented with cattle manure were increased by 41 %–380 % and 16 %–70 % than the other recycled P sources. A structural equation model (SEM) explained 95 % and 91 % of Olsen-P variation in fluvo-aquic and red soils, respectively. Labile P fractions had positive effects on Olsen-P of fluvo-aquic and red soils. 31P-NMR study showed that amount of orthophosphate was the main factor affecting the availability of P from different P sources. In summary, cattle manure was found to be a superior renewable source of P in improving bioavailable P in soil, and its use thus has considerable practical significance in P recycling.
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RC1: 'Comment on soil-2021-127', Anonymous Referee #1, 20 Dec 2021
Phosphorus (P) is an essential crop nutrient but its cycling is still poorly understood. Globally, there are concerns about the long-term sustainability of the rock phosphate reserves that are used to make chemical P fertilizers. The use of recycled wastes, including animal manures, could be used to replace some or all of P fertilizers, but studies are needed to understand the availability of these wastes to crops. The objective of this study was to investigate P availability over time in incubated soils after amendment with recycled wastes, including poultry and cattle manure and maize straw. In general, the topic of the study is suitable for this journal, and could be of interest to readers. However, there are a number of problems with the manuscript that must be addressed before the manuscript can be accepted for publication.
1. This manuscript presents the results of a very simple study: the authors added four fertilizers developed from recycled waste materials, plus a chemical P fertilizer and a check with no fertilizer, to two soils and incubated them for 70 days. They monitored soil test (Olsen) P regularly over the 70-day incubation, but did more detailed analyses on samples incubated for the full 70 days only. However, as the authors themselves point out in the Introduction and the Discussion, incubation studies with organic P sources such as manures are very common, and the majority of the conclusions of this study (e.g., “different P sources had different effects on soil P availability”, “soil Olsen-P content was mainly affected by the labile P fraction”, etc.) have been shown many times before. Therefore, while the results may be useful in the region where this study was conducted, the overall novelty is low as currently written. If this manuscript is revised, the authors must clearly indicate the factors that make this study different from previous studies, including novel results not shown by any previous study.
2. One major concern is the lack of detailed information about the soils used in this study. The authors describe them as “calcareous fluvo-aquic soil in Quzhou” and “red soil in Shilin County” (line 108), and include very limited information about these soils in lines 109-113”. However, in the discussion, they make statements indicating that they view the results of this study to be widely applicable (e.g. “suggests that the application of bone meal in red soil”, lines 273-273; “adding maize straw and cattle bone meal to fluvo-aquic soil”, line 297). The authors need to provide a lot more information about these soils to demonstrate that the results of this study can be more widely applied than to just the soils used in this study.
3. Another concern, related to the previous point, is the incomplete descriptions of the recycled P materials used in this study. The authors seem to assume that “poultry manure”, “cattle manure”, “maize straw” and “cattle bone powder” are adequate descriptions, despite indicating in the introduction that these materials can vary in composition (lines 65-70). based on the literature cited in lines 79-82. However, it is well-established in the literature that this is not true, especially for manure P. Many things will influence P forms and their cycling in manures even within the same species, including diet, animal age and life stage, animal bedding that may be including with animal feces, and storage and treatment of the manures before adding to soils. Diet formulations, including high or low concentrations of dietary P and the addition of phytase has shown to strongly affect P species and concentrations in manure, including for poultry (Maguire et al. 2004 J. Environ. Qual. 33:2306-2316; McGrath et al. 2005 J. Environ. Qual. 34:1896-1909; Leytem et al. 2007 J. Sci. Food Agric. 87:1495-1501), swine (Yi et al. 1996 J. Anim. Sci. 74:1601-1611; Leytem and Thacker 2008 J. Anim. Vet. Advan. 7:113-120), sheep (Leytem et al. 2007 An. Feed. Sci. Technol. 138:13-28) and dairy (Toor et al., 2005 J. Environ. Qual. 34:1380-1391; McDowell et al. 2008 J. Environ. Qual. 37:741-752; He et al. 2009 J. Environ. Qual. 38:1909-1918). Storage conditions, length of storage and amendments during storage, including additives such as phytase or alum will also affect manure P forms and their availability (e.g. Dao et al. 2001 J. Environ. Qual. 30:1693-1698; Moore and Edwards 2007 J. Environ. Qual. 36:163-174; Warren et al. 2008 J. Environ. Qual. 37:469-476; Hill and Cade-Menun 2009 J. Environ. Qual. 38:130-138; Casteel et al. 2011 Poult. Sci. 90:2689-2696; Peirce et al. 2013 Plant Soil 373:359-372; Huang et al. 2018 J. Environ. Qual. 47:345-352).
The authors have provided very limited information about the manures used in this study, beyond the amount of each fertilizer added (Table 1) and some very bad NMR spectra in the supplemental materials. They have not even included P pools from sequential fractionation (Table 2) for the fertilizers. This is not enough. They must include more detailed descriptions of the sources of these manures, including: feed, storage and treatments of manure (if any) during storage; concentrations of agronomically-relevant nutrients and N and P pools in these manures (e.g. Olsen P or other soil test P values; nitrate, ammonium or other soil test N values); total organic P; pH, exchangeable cations, etc.
Without detailed information about the organic fertilizers, it is difficult to extrapolate the results of this study to other manures; instead, the results become specific only to these particular fertilizers in these particular soils. And that is not very relevant scientifically, and will not be of interest to other readers of this journal.
4. The main method for soil P pools was a modified version of the Hedley fractionation method, which the authors used for soils only. Sequential P fraction is a common technique that is widely used. However, this is mainly because it is a simple, inexpensive method, rather than because it is chemically precise. All fractionation methods are operationally-defined, meaning that they are defined by the extractants used and the steps in the fractionation method (the order in which each extractant is used). Most extractants used are not specific for any particular P compounds, with the result that the method yields little meaningful data about specific soil P chemistry, as has been discussed for decades, and which has been demonstrated by comparing fractionation results to those from more advanced techniques such as P k-edge XANES (x-ray adsorption near edge structure) spectroscopy (e.g. Saunders 1959. Nature 4704:2037; Condron and Newman 2011 J. Soil Sediments 11: 830-840; Kar et al. 2011 Soil Sci. 176:589-595; Klotzbücher et al., 2019. J. Plant Nutr. Soil Sci. 182:570-577; Barrow et al., 2021 Plant Soil 459:1-11; Gu and Marginot 2021 Plant Soil 459:13-17).
4a. The authors used a very long extraction procedure, with many of the steps requiring 16 hours of extraction (Fig. S1). However, they do not indicate that they added anti-microbial agents (e.g. toluene, sodium azide). With long extractions such as this, microbial growth can transform P within the samples, either by mineralization of organic P species or by uptake and conversion of phosphate to complex inorganic P forms (e.g. polyphosphates) or organic P forms such as phospholipids or DNA. How certain are the authors that the fractionation results reflect P in the soil samples, and not transformations during the fractionation method?
4b. I am pleased to see that the authors have not labelled the fractions with any specific chemical terms. However, I am concerned that the authors have interpreted changes in these soil fraction as “transformations”(e.g., lines 28, 236, 346). The authors do not provide any information about the fractions in the fertilizers themselves. In my opinion, all the changes they see after incubations reflect the properties of the fertilizers added. If the authors genuinely want to show transformations of soil during the incubation experiment, then they need to provide data for the fertilizer materials and for the soil samples immediately after the fertilizers were added, in addition to data after 70 days of incubations.
4c. I am concerned about the authors’ determination of organic P in their fractions. First, the methods described in lines 138-142 describe the measurement of phosphate colorimetrically in each fraction before and after digestion. The authors are correct that the measurement after digestion is total P (TP) in each extract. However, the colorimetric measurement before digestion is not total inorganic P, but is merely the phosphate that can react with the color reagent (molybdate-reactive P, MRP). Thus, the difference between TP and MRP is not organic P, but is molybdate-unreactive P (MUP), which can include complex inorganic P compounds such as pyrophosphate.
5. A second main method used to characterize P in these samples was 31P nuclear magnetic resonance spectroscopy (P-NMR). The spectra shown in Figs. 4 and S2 are very pool quality. There are also problems with the identification of peaks in these samples. For example, the authors indicate “inositol hexaphosphate” for a general region of the spectra, labelled “C”, rather than identifying any individual peaks. There are several stereoisomers of inositol hexakisphosphates that can be present in spectra of soil extracts, each with multiple peaks that must be identified to confirm the presence of these compounds in samples. In addition, the broad region of the spectra labelled as “C” can contain a number of other compounds, products of diester degradation during sample extraction and analysis. Any peak identification requires spiking samples with known P compounds after the initial P-NMR analysis, and then reanalyzing the samples by P-NMR to confirm peak identifications. If the authors did this, then they need to show the results of these spiking experiments to confirm their peak identifications. If they did not conduct spiking experiments, then they need to do so in order for these P-NMR results to be publishable in any scientific journal.
6. I am also concerned by the authors’ correlation results in Fig. S4. Only independent variables should be correlated with each other. Methods such as NMR and sequential fractionation produce auto-correlated results, not independent variables: NMR because the results are determined as relative proportions, and P fractionation because each fractionation will depend on what is extracted in the previous fraction. Thus, many of the correlation results in Fig. S4 are meaningless because they are not all for independent variables. I am also concerned about the use of structural equation modelling (SEM) to draw conclusions about factors influencing P cycling in these soils, because SEM is merely a fancy method of correlation, and so is governed by the same rules as for simple correlations (e.g., using independent variables), and because I have concerned about the results in general (see previous points).
7. References: there are a number of problems with the references in this manuscript.
7a. The number of references cited is out of proportion to the length of the paper: the total length of the manuscript (including abstract and conclusions) is 326 lines, while the References is 220 lines. The authors should carefully check each reference to see if it is necessary.
7b. There are problems with many of the listings in the References. For example, “Gerard and Frederic” (lines 424-425) and “Gérard” (lines 426-427) are the same reference. The author’s name is Frederic Gérard, which the authors somehow split into to different authors. Unfortunately, they cite both of these in the text (lines 301-302). There are also problems with other references (e.g. Jiang et al. 2012.
8. There are problems with editing and quality of English through the text (e.g., “The relative contents of inorganic and organic P in soil is greatly” should be “The relative contents of inorganic and organic P in soil are greatly”, because the verb modifies “contents”. The authors need to carefully edit any revised manuscript.
Citation: https://doi.org/10.5194/soil-2021-127-RC1 -
AC1: 'Reply on RC1', Yuan Wang, 16 Mar 2022
Dear reviewer,
We greatly appreciate your time and expertise in reviewing our manuscript (soil-2021-127). We have carefully modified the manuscript based on your constructive comments, which significantly improve the manuscript. Appended is our point-by-point response to the comments. The detailed information is as follows:
1. This manuscript presents the results of a very simple study: the authors added four fertilizers developed from recycled waste materials, plus a chemical P fertilizer and a check with no fertilizer, to two soils and incubated them for 70 days. They monitored soil test (Olsen) P regularly over the 70-day incubation but did more detailed analyses on samples incubated for the full 70 days only. However, as the authors themselves point out in the Introduction and the Discussion, incubation studies with organic P sources such as manures are very common, and the majority of the conclusions of this study (e.g., “different P sources had different effects on soil P availability”, “soil Olsen-P content was mainly affected by the labile P fraction”, etc.) have been shown many times before. Therefore, while the results may be useful in the region where this study was conducted, the overall novelty is low as currently written. If this manuscript is revised, the authors must clearly indicate the factors that make this study different from previous studies, including novel results not shown by any previous study.
Thanks for your nice suggestions. Based on the comments, we have conducted a detailed revision in the Introduction. The main objective of this study is to provide a basis for the closed- P cycle in farming systems by recovering P from agricultural wastes. We attempted to explore promising renewable P-containing materials for achieving a closed cycle of P by understanding the transformation dynamics of different renewable P-containing materials in soil and their P availability. The soil texture and physicochemical properties such as pH and organic matter determined the P sorption reaction (Xiong et al., 2022; Debicka et al., 2016; Bouray et al., 2021). Quantifying the transformations of different phosphorus-containing materials in soils with different soil conditions is necessary to enhance phosphorus utilization and reduce phosphorus resource limitation. We have supplemented this background in the introduction.
To understand the transformation dynamics of different P-containing materials in the soil, we measured the P fractions of the initial soil, four renewable P-containing materials, and two soils with different P-containing materials on days 0,35, and 70 of incubation. The P fractions were not significantly different on day 70 of incubation compared to day 0 of incubation. Therefore, we analyzed the data from day 70 of incubation in the manuscript. However, we did not realize that these data are indispensable to understanding the mechanisms of transformation of different P-containing materials in two soils. The analysis and discussion of these data have been supplemented in the modified manuscript. We believe that this study is helpful and meaningful for understanding the mechanisms of P-containing material transformation in different soils.
And the conclusions were modified as follows: Compared with other renewable P-containing materials, CM is a superior source for improving soil P availability in fluvo-aquic and red soils. Compared to fluvo-aquic soil, phosphorus from SSP, PM, and CM was more strongly immobilized in red soil. Further analysis of the P fraction of two soils with different P-containing materials at days 0,35 and 70 of incubation revealed that the distribution of CM to the soil labile P fraction was significantly increased compared to other renewable P-containing materials. And compared with fluvo-aquic soil, the contribution of different P-containing materials to the labile P fraction of red soil was significantly decreased. Changes in P fractions at different incubation periods in soils with different P-containing materials show that most soil P fractions have no significant difference on day 70 of incubation compared to day 0 of incubation. That suggests, in the short term, the difference of potential bioavailability of P from various sources is determined by the distribution to soil labile P fractions rather than its transformation in the soil. In general, there is promising potential to reduce P limitation by recovering cattle manure as an alternative source of P supply. This study provides a basis for closing the P cycle in agricultural systems and for sustainable on-farm P management strategies.
2. One major concern is the lack of detailed information about the soils used in this study. The authors describe them as “calcareous fluvo-aquic soil in Quzhou” and “red soil in Shilin County” (line 108), and include very limited information about these soils in lines 109-113”. However, in the discussion, they make statements indicating that they view the results of this study to be widely applicable (e.g. “suggests that the application of bone meal in red soil”, lines 273-273; “adding maize straw and cattle bone meal to fluvo-aquic soil”, line 297). The authors need to provide a lot more information about these soils to demonstrate that the results of this study can be more widely applied than just the soils used in this study.
Thanks for pointing this out. The transformation process of P in soil is closely related to soil properties. Therefore, we selected two typical soils with different textures and pH for analysis. We have supplemented the details of these two soils in the materials and methods, to provide a reference for the wider application of this study. The modified as follows: Soil samples were collected from fluvo-aquic soil (calcareous alluvial soil) in Hebei Province and red soil (ultisol) in Yunnan Province. The soil texture of fluvo-aquic soil is silt loam soil with 7.9% of clay (<2 μm), 55.3% of silt (2–20 μm), and 36.8% of sand (20–2,000 μm). The soil texture of red soil is clay with 47.5% of clay (<2 μm), 25.3% of silt (2–20 μm), and 27.2% of sand (20–2,000 μm).
3. Another concern, related to the previous point, is the incomplete descriptions of the recycled P materials used in this study. The authors seem to assume that “poultry manure”, “cattle manure”, “maize straw” and “cattle bone powder” are adequate descriptions, despite indicating in the introduction that these materials can vary in composition (lines 65-70). based on the literature cited in lines 79-82. However, it is well-established in the literature that this is not true, especially for manure P. Many things will influence P forms and their cycling in manures even within the same species, including diet, animal age and life stage, animal bedding that may be included with animal feces, and storage and treatment of the manures before adding to soils. Diet formulations, including high or low concentrations of dietary P and the addition of phytase, has shown to strongly affect P species and concentrations in manure, including for poultry (Maguire et al. 2004 J. Environ. Qual. 33:2306-2316; McGrath et al. 2005 J. Environ. Qual. 34:1896-1909; Leytem et al. 2007 J. Sci. Food Agric. 87:1495-1501), swine (Yi et al. 1996 J. Anim. Sci. 74:1601-1611; Leytem and Thacker 2008 J. Anim. Vet. Advan. 7:113-120), sheep (Leytem et al. 2007 An. Feed. Sci. Technol. 138:13-28) and dairy (Toor et al., 2005 J. Environ. Qual. 34:1380-1391; McDowell et al. 2008 J. Environ. Qual. 37:741-752; He et al. 2009 J. Environ. Qual. 38:1909-1918). Storage conditions, length of storage, and amendments during storage, including additives such as phytase or alum, will also affect manure P forms and their availability (e.g. Dao et al. 2001 J. Environ. Qual. 30:1693-1698; Moore and Edwards 2007 J. Environ. Qual. 36:163-174; Warren et al. 2008 J. Environ. Qual. 37:469-476; Hill and Cade-Menu 2009 J. Environ. Qual. 38:130-138; Casteel et al. 2011 Poult. Sci. 90:2689-2696; Peirce et al. 2013 Plant Soil 373:359-372; Huang et al. 2018 J. Environ. Qual. 47:345-352). The authors have provided very limited information about the manures used in this study, beyond the amount of each fertilizer added (Table 1) and some very bad NMR spectra in the supplemental materials. They have not even included P pools from sequential fractionation (Table 2) for the fertilizers. This is not enough. They must include more detailed descriptions of the sources of these manures, including feed, storage, and treatments of manure (if any) during storage; concentrations of agronomically-relevant nutrients, and N and P pools in these manures (e.g. Olsen P or other soil test P values; nitrate, ammonium or other soil test N values); total organic P; pH, exchangeable cations, etc. Without detailed information about the organic fertilizers, it is difficult to extrapolate the results of this study to other manures; instead, the results become specific only to these particular fertilizers in these particular soils. And that is not very relevant scientifically, and will not be of interest to other readers of this journal.
Good suggestion. We have analyzed the basic properties of different P-containing materials including P fractions before the experiment, and the specific information about the four renewable P-containing materials has been supplemented in the materials and methods. For specific data, please refer to the materials and methods and supplementary materials of the revised manuscripts.
As suggested by the reviewers, we have modified as follows: The phosphorus fractions in manure are dependent on various factors, including manure type, solid-liquid separation status, manure removal method, handling way and degree of decomposition, etc (Li et al., 2014; Pagliari and Laboski, 2013). Especially for manure type, the differences in the digestive system and feed composition of different animals cause large differences in phosphorus concentration and fractions in different manures (Garcia-Albacete et al., 2012; Freiberg et al., 2020). Meanwhile, straw turnover is usually applied directly to the soil in agricultural practice, and the P availability in straw requires in-depth analysis (Guan et al., 2020). The bone meal which can be recycled and used as a large amount of organic fertilizer in the future remains unclear in terms of P reuse (Ylivainio et al., 2008). Thus, it is necessary to identify and quantify P fractions from different P-containing materials and their distribution in soil P fractions to determine the potential bioavailability and the environmental impact of P from various sources.
4. The main method for soil P pools was a modified version of the Hedley fractionation method, which the authors used for soils only. Sequential P fraction is a common technique that is widely used. However, this is mainly because it is a simple, inexpensive method, rather than because it is chemically precise. All fractionation methods are operationally-defined, meaning that they are defined by the extractants used and the steps in the fractionation method (the order in which each extractant is used). Most extractants used are not specific for any particular P compounds, with the result that the method yields little meaningful data about specific soil P chemistry, as has been discussed for decades, and which has been demonstrated by comparing fractionation results to those from more advanced techniques such as P K-edge XANES (x-ray absorption near edge structure) spectroscopy (e.g. Saunders 1959. Nature 4704:2037; Condron and Newman 2011 J. Soil Sediments 11: 830-840; Kar et al. 2011 Soil Sci. 176:589-595; Klotzbücher et al., 2019. J. Plant Nutr. Soil Sci. 182:570-577; Barrow et al., 2021 Plant Soil 459:1-11; Gu and Marginot 2021 Plant Soil 459:13-17).
We agree with you that the new techniques such as P K-edge XANES is useful to understanding the soil P transformation progress, while it is difficult for us now due to the crowded monitoring. We will try the advanced techniques to improve our future work.
4a. The authors used a very long extraction procedure, with many of the steps requiring 16 hours of extraction (Fig. S1). However, they do not indicate that they added anti-microbial agents (e.g. toluene, sodium azide). With long extractions such as this, microbial growth can transform P within the samples, either by mineralization of organic P species or by uptake and conversion of phosphate to complex inorganic P forms (e.g. polyphosphates) or organic P forms such as phospholipids or DNA. How certain are the authors that the fractionation results reflect P in the soil samples and not transformations during the fractionation method?
Thanks for pointing out this important point. We strictly follow the improved P sequential fractionation method by Tiessen and Moir. We agree that microorganisms will have an impact on the transformation of P in the long-term extraction process. Therefore, we strictly managed to shake time, environmental temperature, and chromogenic time in the operation of the test. All samples were measured under the same conditions to minimize the effects of P transformation on the results during the extraction process.
4b. I am pleased to see that the authors have not labeled the fractions with any specific chemical terms. However, I am concerned that the authors have interpreted changes in these soil fractions as “transformations” (e.g., lines 28, 236, 346). The authors do not provide any information about the fractions in the fertilizers themselves. In my opinion, all the changes they see after incubations reflect the properties of the fertilizers added. If the authors genuinely want to show transformations of soil during the incubation experiment, then they need to provide data for the fertilizer materials and the soil samples immediately after the fertilizers were added, in addition to data after 70 days of incubations.
Thanks for the helpful suggestions. We have supplemented the data of soil P fractions on days 0 and 35 of incubation in the supplementary materials and supplemented the discussion of these results in the manuscript.
4c. I am concerned about the authors’ determination of organic P in their fractions. First, the methods described in lines 138-142 describe the measurement of phosphate colorimetrically in each fraction before and after digestion. The authors are correct that the measurement after digestion is total P (TP) in each extract. However, the colorimetric measurement before digestion is not total inorganic P but is merely the phosphate that can react with the color reagent (molybdate-reactive P, MRP). Thus, the difference between TP and MRP is not organic P but is molybdate-unreactive P (MUP), which can include complex inorganic P compounds such as pyrophosphate.
Thanks. We followed the improved P sequential fractionation method to classify different P fractions. The P fractions before and after digestion are divided into inorganic P and organic P. We agree with the reviewer's suggestion and annotate this point in the Materials and Methods section of the manuscript.
5. A second main method used to characterize P in these samples was 31P nuclear magnetic resonance spectroscopy (P-NMR). The spectra shown in Figs. 4 and S2 are of very poor quality. There are also problems with the identification of peaks in these samples. For example, the authors indicate “inositol hexaphosphate” for a general region of the spectra, labeled “C”, rather than identifying any individual peaks. There are several stereoisomers of inositol hexakisphosphates that can be present in spectra of soil extracts, each with multiple peaks that must be identified to confirm the presence of these compounds in samples. In addition, the broad region of the spectra labeled as “C” can contain several other compounds, products of diester degradation during sample extraction and analysis. Any peak identification requires spiking samples with known P compounds after the initial P-NMR analysis and then reanalyzing the samples by P-NMR to confirm peak identifications. If the authors did this, then they need to show the results of these spiking experiments to confirm their peak identifications. If they did not conduct spiking experiments, then they need to do so for these P-NMR results to be publishable in any scientific journal.
Thank you for pointing out this lack of detailed information. This information has been supplemented with the modified manuscript.
6. I am also concerned by the authors’ correlation results in Fig. S4. Only independent variables should be correlated with each other. Methods such as NMR and sequential fractionation produce auto-correlated results, not independent variables: NMR because the results are determined as relative proportions, and P fractionation because each fractionation will depend on what is extracted in the previous fraction. Thus, many of the correlation results in Fig. S4 are meaningless because they are not all for independent variables. I am also concerned about the use of structural equation modeling (SEM) to conclude factors influencing P cycling in these soils, because SEM is merely a fancy method of correlation, and so is governed by the same rules as for simple correlations (e.g., using independent variables), and because I have concerned about the results in general (see previous points).
Thanks for the helpful suggestions. We modified the graphical representation of the correlation between Olsen-P and P fractions in the supplementary materials. Please refer to supplementary material figure S4 for specific modifications. Structural equation modeling (SEM) can intuitively show the complex path relationship. SEM is also widely used in the study of the soil P cycle (Hou et al., 2016; Costa et al., 2016; Qaswar et al., 2020). In this study, SEM helps us to better understand the process and environmental factors driving soil P transformation. We have redescribed the SEM results in the modified manuscript.
7. References: there are several problems with the references in this manuscript.
7a. The number of references cited is out of proportion to the length of the paper: the total length of the manuscript (including abstract and conclusions) is 326 lines, while the References is 220 lines. The authors should carefully check each reference to see if it is necessary.
We have updated the references accordingly.
7b. There are problems with many of the listings in the References. For example, “Gerard and Frederic” (lines 424-425) and “Gérard” (lines 426-427) are the same references. The author’s name is Frederic Gérard, which the authors somehow split into two different authors. Unfortunately, they cite both of these in the text (lines 301-302). There are also problems with other references (e.g. Jiang et al. 2012.
Thank you for pointing this out. We have updated the references accordingly.
8. There are problems with editing and quality of English through the text (e.g., “The relative contents of inorganic and organic P in soil is great” should be “The relative contents of inorganic and organic P in soil are great” because the verb modifies “contents”. The authors need to carefully edit any revised manuscript.
We would like to express our heartfelt thanks to the reviewer for the thorough reading of our manuscript and the very useful suggestions. We carefully considered the reviewers' suggestions and made corresponding modifications, which greatly improved our manuscript. During the revision process, we have also done very careful language polishing accordingly.
References of response to referee comments
Bouray, M., Moir, J. L., Lehto, N. J., Condron, L. M., Touhami, D., and Hummel, C.: Soil pH effects on phosphorus mobilization in the rhizosphere of Lupinus angustifolius, Plant and Soil, 469, 387-407, https://doi.org/10.1007/s11104-021-05177-4, 2021.
Costa, M. G., Gama-Rodrigues, A. C., Goncalves, J. L. D., Gama-Rodrigues, E. F., Sales, M. V. D., and Aleixo, S.: Labile and Non-Labile Fractions of Phosphorus and Its Transformations in Soil under Eucalyptus Plantations, Brazil, Forests, 7, https://doi.org/10.3390/f7010015, 2016.
Debicka, M., Kocowicz, A., Weber, J., and Jamroz, E.: Organic matter effects on phosphorus sorption in sandy soils, Archives of Agronomy and Soil Science, 62, 840-855, https://doi.org/10.1080/03650340.2015.1083981, 2016.
Freiberg, Y., Fine, P., Levkovitch, I., and Baram, S.: Effects of the origins and stabilization of biosolids and biowastes on their phosphorous composition and extractability, Waste Management, 113, 145-153, https://doi.org/10.1016/j.wasman.2020.06.002, 2020.
Garcia-Albacete, M., Martin, A., and Cartagena, M. C.: Fractionation of phosphorus biowastes: Characterisation and environmental risk, Waste Management, 32, 1061-1068, https://doi.org/10.1016/j.wasman.2012.02.003, 2012.
Guan, X. K., Wei, L., Turner, N. C., Ma, S. C., Yang, M., and Wang, T. C.: Improved straw management practices promote in situ straw decomposition and nutrient release and increase crop production, Journal of Cleaner Production, 250, 119514.119511-119514.119513, 2020.
Hou, E. Q., Chen, C. R., Kuang, Y. W., Zhang, Y. G., Heenan, M., and Wen, D. Z.: A structural equation model analysis of phosphorus transformations in global unfertilized and uncultivated soils, Global Biogeochemical Cycles, 30, 1300-1309, https://doi.org/10.1002/2016gb005371, 2016.
Li, G., Li, H., Leffelaar, P. A., Shen, J., and Zhang, F.: Characterization of phosphorus in animal manures collected from three (dairy, swine, and broiler) farms in China, PLoS One, 9, e102698, https://doi.org/10.1371/journal.pone.0102698, 2014.
Pagliari, P. H. and Laboski, C. A. M.: Dairy manure treatment effects on manure phosphorus fractionation and changes in soil test phosphorus, Biology and Fertility of Soils, 49, 987-999, https://doi.org/10.1007/s00374-013-0798-2, 2013.
Qaswar, M., Chai, R. S., Ahmed, W., Jing, H., Han, T. F., Liu, K. L., Ye, X. X., Xu, Y. M., Anthonio, C. K., and Zhang, H. M.: Partial substitution of chemical fertilizers with organic amendments increased rice yield by changing phosphorus fractions and improving phosphatase activities in fluvo-aquic soil, Journal of Soils and Sediments, 20, 1285-1296, https://doi.org/10.1007/s11368-019-02476-3, 2020.
Xiong, J., Liu, Z. H., Yan, Y. P., Xu, J. L., Liu, D., Tan, W. F., and Feng, X. H.: Role of clay minerals in controlling phosphorus availability in a subtropical Alfisol, Geoderma, 409, https://doi.org/10.1016/j.geoderma.2021.115592, 2022.
Ylivainio, K., Uusitalo, R., and Turtola, E.: Meat bone meal and fox manure as P sources for ryegrass (Lolium multiflorum) grown on a limed soil, Nutrient Cycling in Agroecosystems, 81, 267-278, https://doi.org/10.1007/s10705-007-9162-y, 2008.
Citation: https://doi.org/10.5194/soil-2021-127-AC1
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AC1: 'Reply on RC1', Yuan Wang, 16 Mar 2022
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CC1: 'Comment on soil-2021-127', Peter Leinweber, 05 Jan 2022
- 1
- 27: The manures and maize straw are P-containing materials but not P fertilizers, sensu stricto.
- 37: Overall, the concluding sentence is very general. Reader in fact remains uninformed, what is novel in this study. No explanation is given for the descriptive findings. For instance, cattle manure performed best but what is the "considerable practical significance" of this finding in P-recycling? ... Using all cattle manure as soil amendments = done anyway; raising more cattle ...? Or, is this an overall meaningless phrase? Authors are vague in their conclusions or remain almost unclear.
- 2
INTRO
l. 46: What in detail are "the attendant ... quality issues"? Vague expression, meaningless if no more details are given.- 64/65: For increases and decreases explained here, different bases were used (proportions vs. contents). Thus, meaning of this statement is unclear. In fact, proportions cannot directly compared with contents/concentrations.
- 3
- 66-69: This literature evaluation is incomplete and rather selective. For sure, much more is known about P in manures and similar materials. All this should have been compiled to disclose real knowledge gaps and lay a basis for the present study. Here it reads rather vague, like "effects are complex and need to be studied". That is not a strong rationale for a laborious scientific study.
- 63-74: Again, references are very incomplete. Much more is known, even on the soil the authors mention at l. 75, 76.
- 73: "contents ... are influenced ...".
- 74-76: Weak conclusive rationale for study. What is meant with “edaphic conditions"?
- 76: "Hedley fractionation" is slang. It is a sequential P fractionation after Hedley et al., modified by Tiessen .... It is a division of total soil P into fractions, not fractions into fractions. Imprecise explanation.
- 78/79: This reference refers to "a subtropical region". For evidencing "wide use" some review articles should have been cited at least (I recommend reading first Cross & Schlesinger).
- 79-82: 2 contrasting statements in 1 sentence but references are not assigned to each of the statements. Unclear for reader....
- 83 ff. As already criticized above for the P fractionation, literature review of 31P NMR is very selective and fragmentary. For instance, not any study of P in manures and other P recycling materials has been mentioned although many of such studies have been published.
4:
l 96: When introducing the soils, authors should use internationally understandable soil units, like the WRB system. "Red" indicates Ferralsols or ferralic subunits of other Major Soil Units, developed from intensive weathering under subtropical/tropical climate conditions. By contrast to this system "Red" as such is not an internationally accepted soil classification; same with "fluvo-aquic" (if not in combination with a WRB unit). This imprecision is hard to understand, considering that the WRB System and secondary literature on it refer to the P issues in great detail.
- 97: "Little is known" is a phrase very often used, but this phrase is meaningless if authors do not communicate what in detail (even if it is not much) is known (… and what is unknown but important to know).
- 100-103: Authors write what they did but they do not report what they intended to find out or what their research hypotheses were. Overall, my impression of the INTRO text is "vague", "not very well reviewed" and "immature" in how the rationale for study was tried to develop.
- MATERIALS & METHODS:
Soil materials should be described in terms of WRB units and soil horizon origin. Instead of "Olsen" the detailed extractant should be given.
- 116-117: This is confusing; better assign the concentrations to each of the materials.
p. 5: - 138-142: Unclear how Pt and Pi were determined if Po is the difference Pt-Pi? Description should be clear and understandable without checking the Figure S1.
l 143: variation? I do think that 31P NMR can quantify species. - 148 ... contains incomplete sentence
RESULTS
l. 176: First of all, I see in Fig. 1, that the differences which appear at the end of incubation are more or less already obvious at the starting point. That indicates that the results reflect inherent properties of the materials added, rather than - or in addition to – the interactions with soil particles. Therefore, the study is incomplete without giving the analyses results for the non-amended soils (maybe controls) and amendments (prior to addition to soil). Study would gain scientific value if the authors would be able to distinguish between effects of materials composition and interaction with soil (the latter leading to differences between soils (… for which details of mineralogy must be known).
l. 180 ff: Differences between treaments better should be explained as factors. Data as percent bear the risk of confusion if basis for calculation is unclear.
l. 177: Olsen P cannot be "improved". This is bad slang. The concentration of NaHCO3-extracted be can be increased by factor of ... (= more precise explanation)- 179-180: Bad wording; better assign factor of increase to each treatment.
Sorry authors, here I stop reading/revising your manuscript. In my view, it is too immature to be seriously reviewed. As a reviewer, I feel wasting my time with your text. A greatly improved version, developed and written with much more care, should be submitted which starts with thorough revision of the pertinent literature, logical deriving knowledge gaps and rationales for study, and testable hypotheses.
>>>> Finally, just a quick jump to the final section >>>>
CONCLUSIONS
l. 339: This is not new but has been shown in many previous studies.
l. 340-348: None of this is conclusion but almost all repetition of previous text. Reader cannot find any original new information from this section.l: 343-344: This is not surprising but could be expected because of same extractant (weak NaHCO3-solution) in sequential extraction and the so-called Olsen-method. As such, it is a meaningless result.
Citation: https://doi.org/10.5194/soil-2021-127-CC1 -
AC3: 'Reply on CC1', Yuan Wang, 16 Mar 2022
Dear Dr. Leinweber,
We greatly appreciate your time and expertise in reviewing our manuscript (soil-2021-127). We have carefully modified the manuscript based on your constructive comments, which significantly improve the manuscript. Appended is our point-by-point response to the comments. The detailed information is as follows:
1. 27: The manures and maize straw are P-containing materials but not P fertilizers, sensu stricto.
Thanks for the nice suggestion. We agree with you and have modified this expression throughout the text.
37: Overall, the concluding sentence is very general. Reader in fact remains uninformed, which is novel in this study. No explanation is given for the descriptive findings. For instance, cattle manure performed best but what is the "considerable practical significance" of this finding in P-recycling? ... Using all cattle manure as soil amendments = done anyway; raising more cattle ...? Or, is this an overall meaningless phrase? Authors are vague in their conclusions or remain almost unclear.
Thanks. Based on your suggestion we have significantly revised the conclusions and highlighted our main findings.
46: What in detail are "the attendant ... quality issues"? Vague expression, meaningless if no more details are given.
Thanks. We have corrected this sentence in the modified manuscript. A modified version is shown as follows: excessive application of phosphate fertilizer is a common phenomenon, which leads to soil P accumulation, water pollution, and crop quality decline.
64/65: For increases and decreases explained here, different bases were used (proportions vs. contents). Thus, the meaning of this statement is unclear. Proportions cannot be directly compared with contents/concentrations.
Thanks. Based on the comments We revise the sentence as follows: Also, application of organic fertilizer increased the proportion of labile organic phosphate (Po) and inositol hexaphosphate (IHP) but decreased stable Ca-associated P proportion.
66-69: This literature evaluation is incomplete and rather selective. For sure, much more is known about P in manures and similar materials. All this should have been compiled to disclose real knowledge gaps and lay a basis for the present study. Here it reads rather vague, like "effects are complex and need to be studied". That is not a strong rationale for a laborious scientific study.
Thanks. As suggested by the reviewers, we have deleted the first sentence and revised the sentence as follows: The P fractions in manure are dependent on various factors, including manure type, solid-liquid separation status, manure removal method, handling way and degree of decomposition, etc (Li et al., 2014a; Pagliari and Laboski, 2013). Especially for manure type, the differences in the digestive system and feed composition of different animals cause large differences in P concentration and fractions in different manures (Garcia-Albacete et al., 2012; Freiberg et al., 2020). Meanwhile, straw turnover is usually applied directly to the soil in agricultural practice, and the P availability in straw requires in-depth analysis (Guan et al., 2020). The bone meal which can be recycled and used as a large amount of organic fertilizer in the future remains unclear in terms of P reuse (Ylivainio et al., 2008). Thus, it is necessary to identify and quantify P fractions from different P-containing materials and their distribution in soil P fractions to determine the potential bioavailability of P from various sources.
63-74: Again, references are very incomplete. Much more is known, even on the soil, the authors mention at l. 75, 76.
As suggested by the reviewers, we have supplemented relevant information in the Introduction section.
73: "contents ... are influenced ...".
Thanks. The initial description has been modified as follows: the relative contents of inorganic and organic P in soil were greatly affected by soil type, land use and the type of organic amendment applied.
74-76: Weak conclusive rationale for the study. What is meant by “edaphic conditions"?
Thank you for your suggestion. We modified the sentence as follows: it is valuable to reveal the transformation mechanism of different P-containing materials in soil and its relationship with soil properties by studying the difference of P fractions in a typical red soil (low pH) and a fluvo-aquic soil (slightly alkaline pH) with different P-containing materials.
76: "Hedley fractionation" is slang. It is a sequential P fractionation after Hedley et al., modified by Tiessen… It is a division of total soil P into fractions, not fractions into fractions. Imprecise explanation.
Thanks. We modified the sentence accordingly.
78/79: This reference refers to "a subtropical region". For evidencing "wide use" some review articles should have been cited at least (I recommend reading first Cross & Schlesinger).
Thank you for the suggestion. We have supplemented the references related to P fractions in other research regions.
79-82: 2 contrasting statements in 1 sentence but references are not assigned to each of the statements. Unclear for the reader…
Thank you. The reference has been modified.
83 ff. As already criticized above for the P fractionation, the literature review of 31P NMR is very selective and fragmentary. For instance, not any study of P in manures and other P recycling materials has been mentioned although many of such studies have been published.
Thank you for the comments. We have supplemented the relevant studies as follows: Previous studies reported that the solution 31P-NMR procedure detected more phytic acid in poultry manure than that in cattle manure (Li et al., 2014b; Jayasundera et al., 2005).
96: When introducing the soils, authors should use internationally understandable soil units, like the WRB system. "Red" indicates Ferralsols or ferric subunits of other Major Soil Units, developed from intensive weathering under subtropical/tropical climate conditions. By contrast to this system, "Red" as such is not an internationally accepted soil classification; same with "fluvo-aquic" (if not in combination with a WRB unit). This imprecision is hard to understand, considering that the WRB System and secondary literature on it refer to the P issues in great detail.
We agree with these comments. We have supplemented the details of these two soils in the materials and methods, to provide a reference for the wider application of this study. The modified as follows: Soil samples were collected from fluvo-aquic soil (calcareous alluvial soil) in Hebei Province and red soil (ultisol) in Yunnan Province. The soil texture of fluvo-aquic soil is silt loam soil with 7.9% of clay (<2 μm), 55.3% of silt (2–20 μm), and 36.8% of sand (20–2,000 μm). The soil texture of red soil is clay with 47.5% of clay (<2 μm), 25.3% of silt (2–20 μm), and 27.2% of sand (20–2,000 μm).
97: "Little is known" is a phrase very often used, but this phrase is meaningless if authors do not communicate what in detail (even if it is not much) is known (and what is unknown but important to know).
Thank you for pointing this out. We have modified it as follows: quantifying the variation of soil P availability on the time scale and in different soil types (representative of acidic and alkaline soils) is worth further investigation.
100-103: Authors write what they did but they do not report what they intended to find out or what their research hypotheses were. Overall, my impression of the INTRO text is "vague", "not very well-reviewed" and "immature" in how the rationale for the study was tried to develop.
We would like to thank the reviewer for her critical and constructive comments. The research objectives and hypothesis has been redrafted at the end of the introduction section. We hypothesized that：(1) Compared with MS, CB, and PM, CM is more efficient renewable P-containing materials. (2) Compared with fluvo-aquic soil, different P-containing materials are more easily fixed in red soil. (3) The difference in potential bioavailability of P from various sources is determined by their distribution to soil labile P fractions.
2. MATERIALS & METHODS:
Soil materials should be described in terms of WRB units and soil horizon origin. Instead of "Olsen" the detailed extractant should be given.
Thanks for the constructive comments. We have supplemented the material methods section with more details on soil properties and Olsen-P extractant.
116-117: This is confusing; better assign the concentrations to each of the materials.
Apologies for this confusing information. We have modified this accordingly.
138-142: Unclear how Pt and Pi were determined if Po is the difference Pt-Pi? The description should be clear and understandable without checking Figure S1.
Thank you for your suggestion. We have modified it as follows: The concentration of Po is equal to the concentration of total P (Pt) minus the concentration of inorganic P (Pi).
143: variation? I do think that 31P NMR can quantify species.
Thank you for your suggestion. The title has been modified.
148: contains the incomplete sentence
Thank you for pointing this out. The sentence has been modified as follows: the solution pH was adjusted to 9.0±1.0, kept steady for 30 min, and again centrifuged at 12000 g (20 ℃) for 30 minutes.
3. 176: First of all, I see in Fig. 1, that the differences which appear at the end of incubation are more or less already obvious at the starting point. That indicates that the results reflect inherent properties of the materials added, rather than - or in addition to – the interactions with soil particles. Therefore, the study is incomplete without giving the analyses results for the non-amended soils (maybe controls) and amendments (prior to addition to soil). The study would gain scientific value if the authors would be able to distinguish between effects of materials composition and interaction with soil (the latter leading to differences between soils (… for which details of mineralogy must be known).
Thank you for these valuable comments. The analysis and discussion of these data have been supplemented in the modified manuscript accordingly.
180 ff: Differences between treatments better should be explained as factors. Data as percent bear the risk of confusion if the basis for calculation is unclear.
Thank you for your suggestion. The expression has been modified as follows: During 0-70 days of incubation, the Olsen-P concentration of SSP, PM and CM enriched fluvo-aquic soil has increased by 49.5 mg·kg-1, 21.7 mg·kg-1, and 34.4 mg·kg-1 compared with CK in average, respectively. In SSP, PM, and CM enriched red soil, the Olsen-P concentration was increased by 29.9 mg·kg-1 15.3 mg·kg-1 and 23.8 mg·kg-1 compared with CK on average during 0-70 days of incubation, respectively. CM outperformed other renewable P-containing materials in increasing Olsen-P concentration. In fluvo-aquic soil, the Olsen-P concentration of soil with CM was significantly increased by 12.7 mg·kg-1, 34.5 mg·kg-1, and 34.24 mg·kg-1 on average compared with PM, MS, and CB, respectively. In red soil, the Olsen-P concentration of soil with CM was significantly increased by 8.5 mg·kg-1, 25.3 mg·kg-1, and 19.4 mg·kg-1 on average compared with PM, MS, and CB, respectively.
177: Olsen P cannot be "improved". This is bad slang. The concentration of NaHCO3-extracted be can be increased by a factor of ... (= more precise explanation)
Thank you for pointing this out. The expression has been modified as follows: based on the effect size, treatments could be grouped into (1) those that significantly increased Olsen-P concentration and (2) those that slightly or insignificantly increased Olsen-P concentration, following soil enrichment with different P-containing materials.
179-180: Bad wording; better assign factor of increase to each treatment.
Thank you for pointing this out. We have modified it accordingly.
Sorry authors, here I stop reading/revising your manuscript. In my view, it is too immature to be seriously reviewed. As a reviewer, I feel wasting my time with your text. A greatly improved version, developed and written with much more care, should be submitted which starts with a thorough revision of the pertinent literature, logical deriving knowledge gaps and rationales for study, and testable hypotheses.
We sincerely accept these criticisms. The main objective of this study is to provide a basis for the closed- P cycle in farming systems by recovering P from agricultural wastes. We attempted to explore promising renewable P-containing materials for achieving a closed cycle of P by understanding the transformation dynamics of different renewable P-containing materials in soil and their P availability. The soil texture and physicochemical properties such as pH and organic matter determined the P sorption reaction (Xiong et al., 2022; Debicka et al., 2016; Bouray et al., 2021). Quantifying the transformations of different P-containing materials in soils with different soil conditions is necessary to enhance P utilization and reduce P resource limitation. We have supplemented this background in the introduction.
To understand the transformation dynamics of different P-containing materials in the soil, we measured the P fractions of the initial soil, four renewable P-containing materials, and two soils with different P-containing materials on days 0,35, and 70 of incubation. As mentioned by the reviewers, the differences which appear at the end of incubation are more or less already obvious at the starting point. The P fractions were not significantly different on day 70 of incubation compared to day 0 of incubation. Therefore, we analyzed the data from day 70 of incubation in manuscript. However, we did not realize that these data are indispensable to understanding the mechanisms of transformation of different P-containing materials in two soils. The analysis and discussion of these data have been supplemented in the modified manuscript. These comments have greatly improved our manuscript. We believe that this study is valuable and meaningful for understanding the mechanisms of P-containing material transformation in different soils.
4. CONCLUSIONS
339: This is not new but has been shown in many previous studies.
340-348: None of this is a conclusion but almost all repetition of the previous text. The reader cannot find any original new information from this section.
343-344: This is not surprising but could be expected because of the same extractant (weak NaHCO3-solution) in sequential extraction and the so-called Olsen method. As such, it is a meaningless result.
We express our sincere appreciation for your careful work and thoughtful suggestions. These comments were valuable and helpful in revising and improving the manuscript. The abstracts have been significantly revised and the conclusions have been rewritten.
The conclusions were modified as follows: Compared with other renewable P-containing materials, CM is a superior source for improving soil P availability in fluvo-aquic and red soils. Compared to fluvo-aquic soil, phosphorus from SSP, PM, and CM was more strongly immobilized in red soil. Further analysis of the P fraction of two soils with different P-containing materials at days 0,35 and 70 of incubation revealed that the distribution of CM to the soil labile P fraction was significantly increased compared to other renewable P-containing materials. And compared with fluvo-aquic soil, the contribution of different P-containing materials to the labile P fraction of red soil was significantly decreased. Changes in P fractions at different incubation periods in soils with different P-containing materials show that most soil P fractions have no significant difference on day 70 of incubation compared to day 0 of incubation. That suggests, in the short term, the difference of potential bioavailability of P from various sources is determined by the distribution to soil labile P fractions rather than its transformation in the soil. In general, there is promising potential to reduce P limitation by recovering cattle manure as an alternative source of P supply. This study provides a basis for closing the P cycle in agricultural systems and for sustainable on-farm P management strategies.
Thank you again for your suggestions and help, and we look forward to receiving your suggestions for our revised manuscript again.
References of response to referee comments
Bouray, M., Moir, J. L., Lehto, N. J., Condron, L. M., Touhami, D., and Hummel, C.: Soil pH effects on phosphorus mobilization in the rhizosphere of Lupinus angustifolius, Plant and Soil, 469, 387-407, https://doi.org/10.1007/s11104-021-05177-4, 2021.
Debicka, M., Kocowicz, A., Weber, J., and Jamroz, E.: Organic matter effects on phosphorus sorption in sandy soils, Archives of Agronomy and Soil Science, 62, 840-855, https://doi.org/10.1080/03650340.2015.1083981, 2016.
Freiberg, Y., Fine, P., Levkovitch, I., and Baram, S.: Effects of the origins and stabilization of biosolids and biowastes on their phosphorous composition and extractability, Waste Management, 113, 145-153, https://doi.org/10.1016/j.wasman.2020.06.002, 2020.
Garcia-Albacete, M., Martin, A., and Cartagena, M. C.: Fractionation of phosphorus biowastes: Characterisation and environmental risk, Waste Management, 32, 1061-1068, https://doi.org/10.1016/j.wasman.2012.02.003, 2012.
Guan, X. K., Wei, L., Turner, N. C., Ma, S. C., Yang, M., and Wang, T. C.: Improved straw management practices promote in situ straw decomposition and nutrient release and increase crop production, Journal of Cleaner Production, 250, 119514.119511-119514.119513, 2020.
Jayasundera, S., , W. F. S., III, J. B. R., and Dao, T. H.: Direct 31P NMR spectroscopic measurement of phosphorus forms in dairy manures, Journal of Food, Agriculture & Environment, 3, 5, 2005.
Li, G., Li, H., Leffelaar, P. A., Shen, J., and Zhang, F.: Characterization of phosphorus in animal manures collected from three (dairy, swine, and broiler) farms in China, PLoS One, 9, e102698, https://doi.org/10.1371/journal.pone.0102698, 2014a.
Li, G. H., Li, H. G., Leffelaar, P. A., Shen, J. B., and Zhang, F. S.: Characterization of Phosphorus in Animal Manures Collected from Three (Dairy, Swine, and Broiler) Farms in China, Plos One, 9, https://doi.org/10.1371/journal.pone.0102698, 2014b.
Pagliari, P. H. and Laboski, C. A. M.: Dairy manure treatment effects on manure phosphorus fractionation and changes in soil test phosphorus, Biology and Fertility of Soils, 49, 987-999, https://doi.org/10.1007/s00374-013-0798-2, 2013.
Xiong, J., Liu, Z. H., Yan, Y. P., Xu, J. L., Liu, D., Tan, W. F., and Feng, X. H.: Role of clay minerals in controlling phosphorus availability in a subtropical Alfisol, Geoderma, 409, https://doi.org/10.1016/j.geoderma.2021.115592, 2022.
Ylivainio, K., Uusitalo, R., and Turtola, E.: Meat bone meal and fox manure as P sources for ryegrass (Lolium multiflorum) grown on a limed soil, Nutrient Cycling in Agroecosystems, 81, 267-278, https://doi.org/10.1007/s10705-007-9162-y, 2008.
Citation: https://doi.org/10.5194/soil-2021-127-AC3
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RC2: 'Comment on soil-2021-127', Chiara Pistocchi, 14 Feb 2022
The manuscript of Wang and colleagues reports the effect of four organic amendments/fertilizers on phosphorus (P) pools in two different soils assessed through an incubation experiment. The soil P pools are investigated by sequential P fractionation and 31P solution nuclear magnetic resonance (NMR). The subject is relevant and timely as it deals with the recycling of P in order to reduce the use of mineral P fertilizers, which are produced from non-renewable resources. Although the manuscript is well structured and the experiment is well designed, some major points need to be addressed before publication. See specific comments.
Specific comments:
The main issue in my opinion is the lack of mechanistic interpretation of the reported findings. The effect of organic amendments or fertilizers on soil P has been investigate by several studies, see the non-exhaustive list of references reported below. The authors need to highlight better how their work allows advancing in the understanding of mechanisms driving P availability after the addition of organic amendments and what is the general interest of their research. This issue is also evident from the lack of scientific questions or hypotheses in the introduction, where only operational goals are reported (L98-103)
Motavalli, P., and R. Miles. "Soil phosphorus fractions after 111 years of animal manure and fertilizer applications." Biology and fertility of soils 36.1 (2002): 35-42.
Waldrip, Heidi M., Zhongqi He, and M. Susan Erich. "Effects of poultry manure amendment on phosphorus uptake by ryegrass, soil phosphorus fractions and phosphatase activity." Biology and Fertility of Soils 47.4 (2011): 407-418.
Halajnia, Akram, et al. "Phosphorus fractions in calcareous soils amended with P fertilizer and cattle manure." Geoderma 150.1-2 (2009): 209-213.
Kashem, Md Abul, Olalekan Oluwole Akinremi, and Geza Joseph Racz. "Phosphorus fractions in soil amended with organic and inorganic phosphorus sources." Canadian Journal of Soil Science 84.1 (2004): 83-90.
Brod, Eva, et al. "Waste products as alternative phosphorus fertilisers part I: inorganic P species affect fertilisation effects depending on soil pH." Nutrient Cycling in Agroecosystems 103.2 (2015): 167-185.
Brod, E., Øgaard, A.F., Haraldsen, T.K. et al. Waste products as alternative phosphorus fertilisers part II: predicting P fertilisation effects by chemical extraction. Nutr Cycl Agroecosyst 103, 187–199 (2015). https://doi.org/10.1007/s10705-015-9731-4
A second point is about the recycled fertilizer/amendment material: why these specific materials were chosen? For example, why including maize straw, which is commonly left in the field and therefore do not constitute an external P input? In addition, these materials are poorly characterized. The total NPK contents are not sufficient to characterize these materials as already pointed out by the first reviewer. Information concerning the repartition between inorganic and organic P as well as the water-soluble or bicarbonate-soluble P forms in the fertilizers should be provided. I wonder why the sequential extraction was not performed on these products. A more detailed characterization of the applied material would help a more mechanistic interpretation of the results. Additional variables, such as dissolved and total organic carbon in these products, would help interpret the results. Dissolved organic compounds, for example might displace some adsorbed phosphorus, thus increasing its availability. The discussion Section “Large variability for soil P availability…” would greatly benefit and be less speculative if a more detailed characterization of the organic materials was performed.
The third point concerns the data analysis and other soil variables. The Olsen P and labile P fractions from the sequential extraction are correlated in the structural equation model because the P extracted with these two procedures is largely the same (L232-234 and L343-344). For this reason, it is confusing to state that “the labile P fractions and the moderately labile P fractions had positive effects on soil Olsen P” (L232-233) and other similar expressions. To provide a more mechanistic understanding using the SEM, it would be useful to include independent soil variables, such as clay content, iron oxides content, soluble organic carbon (which is expected to vary with the addition of organic material), which are all known to influence the sorption/desorption reactions of P in soils and therefore its availability.
It is also not clear which data were used to build the SEM, i.e. corresponding to which time points of the incubation.
Finally, language editing is needed, paying attention also to terminology. For example, the P fractions are most of the time called labile/moderately labile etc., but sometimes the words “stable” or “active” or “inert” are used. This might create confusion, as these terms are not specifically defined. I suggest adopting a consistent terminology throughout the manuscript. Another point: according to their NPK content, some of the organic products, ex maize straw, are technically amendments and not fertilizers.
Minor comments:
Please check throughout the manuscript the numbers after the decimal point in the percentages (sometimes zero, sometimes one or two numbers are shown, ex line 181, line 200, line 206) and homogenise to significant precision.
L45-46: “the attendant environmental…” unclear formulation, please revise
L58: “it also affects” not clear what it refers to
L79-80: there are many papers published on the effect of organic fertilizers/amendments on soil P fractions (see the non-exhaustive list above). I suggest checking and integrating this literature into the introduction
L109-112: other properties of the two soils such as the mineralogy or at least the texture would be useful, as well as a classification of the soils such as according the international World Reference Base (WRB)
L117: please, specify whether the P and K concentration in the products are given as P2O5 and K2O or as P and K. It is always preferable to express them as P and K, see:
Lambers, Hans, and N. J. Barrow. "Pervasive use of P2O5, K2O, CaO, MgO, and basic cations, none of which exist in soil." Biology and Fertility of Soils 56.6 (2020): 743-745.
L127: please, specify to what the percent of soil moisture is referred to, e.g. water holding capacity or soil weight …
L122-123: what is the rationale of this quantity of P added?
L143: “quantitation” is rather “quantification”?
L184: what are these ranges referred to? Is that the time points?
L190: “soil P fractions” instead of “fractionations”
L191-192 and L214: does the P added was completely recovered in the extracted fractions or not? This information is not easy to infer from table 2 or figure 3 but it would be useful to verify how much of the added P was not accounted for in the sequential extraction end ended up into non-extractable P.
L225-226: “and more inositol… both soils” awkward formulation, please re-word
L226 “supplemented both soil”, please reformulate
L269: what “drab soil” means?
L279 “found rapid integration” please, reformulate this sentence
L307-310: please refer to the supplementary figure showing pH values.
L343-344: The P extracted with the Olsen extractant largely overlaps with the labile fractions of the sequential extraction. See also the third main point.
Tables and figures
Table 2: I am surprised by the very good precision of the measurements in some fractions, such as in the NaOH-Po, for which, in my experience, the variability usually is quite large. Are those analytical or real replicates?
Not all the figures in supplementary materials are referenced in the text
Citation: https://doi.org/10.5194/soil-2021-127-RC2 -
AC2: 'Reply on RC2', Yuan Wang, 16 Mar 2022
Dear Dr. Pistocchi,
We greatly appreciate your time and expertise in reviewing our manuscript (soil-2021-127). We have carefully modified the manuscript based on your constructive comments, which significantly improve the manuscript. Appended is our point-by-point response to the comments. The detailed information is as follows:
1. The main issue in my opinion is the lack of mechanistic interpretation of the reported findings. The effect of organic amendments or fertilizers on soil P has been investigated by several studies, see the non-exhaustive list of references reported below. The authors need to highlight better how their work allows advancing in the understanding of mechanisms driving P availability after the addition of organic amendments and what is the general interest of their research. This issue is also evident from the lack of scientific questions or hypotheses in the introduction, where only operational goals are reported (L98-103).
Good suggestion. The application of organic fertilizer in agriculture as a soil structure improvement and nitrogen source has been widely studied. While the problem of high environmental risk caused by a large amount of P in organic fertilizer is becoming more and more prominent. Therefore, this study focuses on the soil P transformation from different renewable P-containing materials and aims to quantify the variation of soil P availability on the time scale and in different soil types (representative of acidic and alkaline soils). Based on the suggestion, we supplement the scientific hypotheses in the Introduction as follows: We hypothesized that：(1) Compared with MS, CB, and PM, CM is more efficient renewable P-containing materials. (2) Compared with fluvo-aquic soil, different P-containing materials are more easily fixed in red soil. (3) The difference in potential bioavailability of P from various sources is determined by their distribution to soil labile P fractions.
We attempted to explore promising renewable P-containing materials for achieving a closed cycle of P by understanding the transformation dynamics of different renewable P-containing materials in soil and their P availability. We have supplemented this background in the introduction. To understand the transformation dynamics of different P-containing materials in the soil, we measured the P fractions of the initial soil, four renewable P-containing materials, and two soils with different P-containing materials on days 0,35, and 70 of incubation. The P fractions were not significantly different on day 70 of incubation compared to day 0 of incubation. Therefore, we analyzed the data from day 70 of incubation in the manuscript. However, we did not realize that these data are indispensable to understanding the mechanisms of transformation of different P-containing materials in two soils. The analysis and discussion of these data have been supplemented in the modified manuscript. We believe that this study is helpful and meaningful for understanding the mechanisms of P-containing material transformation in different soils.
And the conclusions were modified as follows: Compared with other renewable P-containing materials, CM is a superior source for improving soil P availability in fluvo-aquic and red soils. Compared to fluvo-aquic soil, phosphorus from SSP, PM, and CM were more strongly immobilized in red soil. Further analysis of the P fraction of two soils with different P-containing materials at days 0,35 and 70 of incubation revealed that the distribution of CM to the soil labile P fraction was significantly increased compared to other renewable P-containing materials. And compared with fluvo-aquic soil, the contribution of different P-containing materials to the labile P fraction of red soil was significantly decreased. Changes in P fractions at different incubation periods in soils with different P-containing materials show that most soil P fractions have no significant difference on day 70 of incubation compared to day 0 of incubation. That suggests, in the short term, the difference of potential bioavailability of P from various sources is determined by the distribution to soil labile P fractions rather than its transformation in the soil. In general, there is promising potential to reduce P limitation by recovering cattle manure as an alternative source of P supply. This study provides a basis for closing the P cycle in agricultural systems and for sustainable on-farm P management strategies.
2. A second point is about the recycled fertilizer/amendment material: why these specific materials were chosen? For example, why include maize straw, which is commonly left in the field and therefore does not constitute an external P input? In addition, these materials are poorly characterized. The total NPK contents are not sufficient to characterize these materials as already pointed out by the first reviewer. Information concerning the repartition between inorganic and organic P as well as the water-soluble or bicarbonate-soluble P forms in the fertilizers should be provided. I wonder why the sequential extraction was not performed on these products. A more detailed characterization of the applied material would help a more mechanistic interpretation of the results. Additional variables, such as dissolved and total organic carbon in these products, would help interpret the results. Dissolved organic compounds, for example, might displace some adsorbed phosphorus, thus increasing its availability. The Discussion Section “Large variability for soil P availability…” would greatly benefit and be less speculative if a more detailed characterization of the organic materials was performed.
Thanks. In this study, we choose poultry manure, cattle manure, maize straw, and bone meal as the renewable P-containing materials to conduct research. Poultry manure and cattle manure is widely used as renewable P-containing materials in current agricultural production. More importantly, the composition of manure P is affected by the digestive system difference between ruminants and non-ruminants, and the role of this difference in the subsequent P transformation process needs further study (Freiberg et al., 2020; Li et al., 2014). Meanwhile, straw turnover is usually applied directly to the soil in agricultural practice, and the P availability in straw requires in-depth analysis. The bone meal which can be recycled and used as a large amount of organic fertilizer in the future remains unclear in terms of P reuse (Ylivainio et al., 2008). We have supplemented the description of the organic materials in the Introduction.
As suggested, we analyzed all P-containing materials including total organic carbon and P fractions and other physicochemical properties before the start of incubation experiments. We have supplemented this detailed information in the modified manuscript. And we supplemented the discussion related to the P forms from raw materials.
3. The third point concerns the data analysis and other soil variables. The Olsen P and labile P fractions from the sequential extraction are correlated in the structural equation model because the P extracted with these two procedures is largely the same (L232-234 and L343-344). For this reason, it is confusing to state that the labile P fractions and the moderately labile P fractions had positive effects on soil Olsen P (L232-233) and other similar expressions. To provide a more mechanistic understanding using the SEM, it would be useful to include independent soil variables, such as clay content, iron oxides content, soluble organic carbon (which is expected to vary with the addition of organic material), which are all known to influence the sorption/desorption reactions of P in soils and therefore its availability.
Thanks for your suggestion. We attempted to better understand the contribution of different P fractions to the variation of soil Olsen-P concentration and the effects of environmental factors on P transformation by structural equation modeling. We have redescribed the SEM results in the modified manuscript.
It is also not clear which data were used to build the SEM, i.e. corresponding to which time points of the incubation.
Thanks. All data for the structural equation modeling were obtained from measurements on day 70 of incubation. We have supplemented this information in the modified manuscript.
Finally, language editing is needed, paying attention also to terminology. For example, the P fractions are most of the time called labile/moderately labile, etc., but sometimes the words “stable” or “active” or “inert” are used. This might create confusion, as these terms are not specifically defined. I suggest adopting consistent terminology throughout the manuscript. Another point: according to their NPK content, some of the organic products, ex maize straw, are technical amendments and not fertilizers.
Good suggestions. During the revision process, we have also done very careful language polishing accordingly. We carefully proofread the whole manuscript and standardized the terminology throughout the manuscript. In addition, we agreed with the reviewers' suggestion to define organic production as fertilizers are not strictly. We have modified the expression throughout the text accordingly.
Minor comments:
Please check throughout the manuscript the numbers after the decimal point in the percentages (sometimes zero, one or two numbers are shown, ex line 181, line 200, line 206) and homogenize to significant precision.
Thank you. We have improved this in the modified manuscript by homogenizing the number of decimal places in percentages to one digit throughout the manuscript.
L45-46: “the attendant environmental…” unclear formulation, please revise.
We have revised the sentence as follows: excessive application of phosphate fertilizer is a common phenomenon, which leads to soil P accumulation, water pollution, and crop quality decline.
L58: “it also affects” not clear what it refers to
Thanks. We have revised the sentence as follows: These renewable P-containing materials can also affect the P kinetics of the soil by changing the adsorption capacity of the soil to P.
L79-80: there are many papers published on the effect of renewable P-containing materials/amendments on soil P fractions (see the non-exhaustive list above). I suggest checking and integrating this literature into the introduction
Thanks for your suggestions. We have supplemented the introduction to the modified manuscript with a description of these research advances. And, the initial sentence has been modified as follows: Quantifying the transformations of different P-containing materials in soils with different soil conditions is necessary to enhance P utilization and reduce P resource limitation.
L109-112: other properties of the two soils such as the mineralogy or at least the texture would be useful, as well as a classification of the soils such as according to the international World Reference Base (WRB)
We agree with these comments. We have supplemented the details of these two soils in the materials and methods, to provide a reference for the wider application of this study. The modified as follows: Soil samples were collected from fluvo-aquic soil (calcareous alluvial soil) in Hebei Province and red soil (ultisol) in Yunnan Province. The soil texture of fluvo-aquic soil is silt loam soil with 7.9% of clay (<2 μm), 55.3% of silt (2–20 μm), and 36.8% of sand (20–2,000 μm). The soil texture of red soil is clay with 47.5% of clay (<2 μm), 25.3% of silt (2–20 μm), and 27.2% of sand (20–2,000 μm).
L117: please, specify whether the P and K concentration in the products are given as P2O5 and K2O or as P and K. It is always preferable to express them as P and K, see:
Thanks. The P, K concentrations of all P-containing materials are indicated by total P and total potassium. We have emphasized this in the Materials Methods section of the modified manuscript.
L127: please, specify to what the percent of soil moisture is referred to, e.g. water holding capacity or soil weight …
We have modified the sentence as follows: During the whole incubation stage, the gravimetric soil water content was kept at about 30% by soil weighing.
L122-123: what is the rationale for this quantity of P added?
The amount of P addition is based on the sufficient soil P amount of most crops to ensure the growth which is derived from the previous study (Kamran et al., 2019; Frazao et al., 2019). We have supplemented the modified manuscript with citations to relevant publications.
L143: “quantitation” is rather “quantification”?
This word has been modified accordingly.
L184: what are these ranges referred to? Are those the time points?
Data refer to the percentage increase in Olsen-P concentration in soils with CM compared to soils with other renewable P-containing materials. The description has been modified in the manuscript.
L190: “soil P fractions” instead of “fractionations”
Thank you. We have modified this in the manuscript.
L191-192 and L214: does the P added was completely recovered in the extracted fractions or not? This information is not easy to infer from table 2 or figure 3 but it would be useful to verify how much of the added P was not accounted for in the sequential extraction end ended up into non-extractable P.
Thank you for your suggestion. Except for the maize straw, all P-containing materials were well recovered during the measurements. We have supplemented the discussion of this result in the manuscript.
L225-226: “and more inositol… both soils” awkward formulation, please re-word
Thank you for pointing this out. We have revised the sentence as follows: Compared with other P-containing materials, the content of inositol hexakisphosphate in the two soils with PM increased significantly " in the modified manuscript.
L226 “supplemented both soils”, please reformulate
Thank you. We have revised the sentence as follows: Although the detected signals were weak, compared with SSP, more signals monoester P and inositol hexakisphosphate were detected in fluvo-aquic soil and red soil with PM and CM.
L269: what does “drab soil” means?
"drab soil" is a soil class according to the Chinese soil genetic classification, which corresponds to the Alfisols of the Soil Taxonomy, and here we follow the author's expression in the cited publication.
L279 “found rapid integration” please, reformulate this sentence
We have modified this in the manuscript.
L307-310: please refer to the supplementary figure showing pH values.
Thank you for your suggestions. We have supplemented the modified manuscript with a description of the changes of pH in soil with different P-containing materials.
L343-344: The P extracted with the Olsen extractant largely overlaps with the labile fractions of the sequential extraction. See also the third main point.
Thank you for your suggestion. We have redescribed the results of structural equation modeling in the modified manuscript.
Table 2: I am surprised by the very good precision of the measurements in some fractions, such as in the NaOH-Po, for which, in my experience, the variability usually is quite large. Are those analytical or real replicates?
We sieved all P-containing materials and soil through a 2 mm sieve before arranging the test and then mixed the soil with the P-containing materials thoroughly. And the samples were well mixed when collecting the samples. This was done to minimize errors caused by the uneven distribution of the samples. And, we strictly managed the environmental temperature and chromogenic time in the operation of the test. All samples were measured under the same conditions to minimize the effects of P transformation on the results during the extraction process. We believe that these results can be reproduced.
Not all the figures in supplementary materials are referenced in the text
Thank you for your suggestion. We have checked the whole manuscript in detail and supplemented the modified manuscript with a description of all the tables and figures in the supplementary materials.
References of response to referee comments
Frazao, J. J., Benites, V. D., Ribeiro, J. V. S., Pierobon, V. M., and Lavres, J.: Agronomic effectiveness of a granular poultry litter-derived organometal phosphate fertilizer in tropical soils: Soil phosphorus fractionation and plant responses, Geoderma, 337, 582-593, https://doi.org/10.1016/j.geoderma.2018.10.003, 2019.
Freiberg, Y., Fine, P., Levkovitch, I., and Baram, S.: Effects of the origins and stabilization of biosolids and biowastes on their phosphorous composition and extractability, Waste Management, 113, 145-153, https://doi.org/10.1016/j.wasman.2020.06.002, 2020.
Kamran, M. A., Xu, R. K., Li, J. Y., Jiang, J., and Shi, R. Y.: Impacts of chicken manure and peat-derived biochars and inorganic P alone or in combination on phosphorus fractionation and maize growth in an acidic ultisol, Biochar, 1, 283-291, https://doi.org/10.1007/s42773-019-00022-5, 2019.
Li, G. H., Li, H. G., Leffelaar, P. A., Shen, J. B., and Zhang, F. S.: Characterization of Phosphorus in Animal Manures Collected from Three (Dairy, Swine, and Broiler) Farms in China, Plos One, 9, https://doi.org/10.1371/journal.pone.0102698, 2014.
Ylivainio, K., Uusitalo, R., and Turtola, E.: Meat bone meal and fox manure as P sources for ryegrass (Lolium multiflorum) grown on a limed soil, Nutrient Cycling in Agroecosystems, 81, 267-278, https://doi.org/10.1007/s10705-007-9162-y, 2008.
Citation: https://doi.org/10.5194/soil-2021-127-AC2
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AC2: 'Reply on RC2', Yuan Wang, 16 Mar 2022
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EC1: 'Comment on soil-2021-127', Luisella Celi, 25 Apr 2022
Dear Authors,
I have completed my evaluation of your manuscript, after your reply to reviewers comments. Your replies have been addressed very carefully, but the criticisms were hard and require a major revision of your paper. As I wrote in the previous evaluation, I invite you to resubmit your manuscript incorporating all revisions you suggested in the replies. Please resubmit your revised manuscript soon.
When revising your manuscript, please consider all issues mentioned in the reviewers' comments carefully. Please note that your revised submission may need to be re-reviewed, due to the strong criticisms arosen by the reviewers.
Kind regards,
Luisella Celi
Topical Editor
Citation: https://doi.org/10.5194/soil-2021-127-EC1
Status: closed
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RC1: 'Comment on soil-2021-127', Anonymous Referee #1, 20 Dec 2021
Phosphorus (P) is an essential crop nutrient but its cycling is still poorly understood. Globally, there are concerns about the long-term sustainability of the rock phosphate reserves that are used to make chemical P fertilizers. The use of recycled wastes, including animal manures, could be used to replace some or all of P fertilizers, but studies are needed to understand the availability of these wastes to crops. The objective of this study was to investigate P availability over time in incubated soils after amendment with recycled wastes, including poultry and cattle manure and maize straw. In general, the topic of the study is suitable for this journal, and could be of interest to readers. However, there are a number of problems with the manuscript that must be addressed before the manuscript can be accepted for publication.
1. This manuscript presents the results of a very simple study: the authors added four fertilizers developed from recycled waste materials, plus a chemical P fertilizer and a check with no fertilizer, to two soils and incubated them for 70 days. They monitored soil test (Olsen) P regularly over the 70-day incubation, but did more detailed analyses on samples incubated for the full 70 days only. However, as the authors themselves point out in the Introduction and the Discussion, incubation studies with organic P sources such as manures are very common, and the majority of the conclusions of this study (e.g., “different P sources had different effects on soil P availability”, “soil Olsen-P content was mainly affected by the labile P fraction”, etc.) have been shown many times before. Therefore, while the results may be useful in the region where this study was conducted, the overall novelty is low as currently written. If this manuscript is revised, the authors must clearly indicate the factors that make this study different from previous studies, including novel results not shown by any previous study.
2. One major concern is the lack of detailed information about the soils used in this study. The authors describe them as “calcareous fluvo-aquic soil in Quzhou” and “red soil in Shilin County” (line 108), and include very limited information about these soils in lines 109-113”. However, in the discussion, they make statements indicating that they view the results of this study to be widely applicable (e.g. “suggests that the application of bone meal in red soil”, lines 273-273; “adding maize straw and cattle bone meal to fluvo-aquic soil”, line 297). The authors need to provide a lot more information about these soils to demonstrate that the results of this study can be more widely applied than to just the soils used in this study.
3. Another concern, related to the previous point, is the incomplete descriptions of the recycled P materials used in this study. The authors seem to assume that “poultry manure”, “cattle manure”, “maize straw” and “cattle bone powder” are adequate descriptions, despite indicating in the introduction that these materials can vary in composition (lines 65-70). based on the literature cited in lines 79-82. However, it is well-established in the literature that this is not true, especially for manure P. Many things will influence P forms and their cycling in manures even within the same species, including diet, animal age and life stage, animal bedding that may be including with animal feces, and storage and treatment of the manures before adding to soils. Diet formulations, including high or low concentrations of dietary P and the addition of phytase has shown to strongly affect P species and concentrations in manure, including for poultry (Maguire et al. 2004 J. Environ. Qual. 33:2306-2316; McGrath et al. 2005 J. Environ. Qual. 34:1896-1909; Leytem et al. 2007 J. Sci. Food Agric. 87:1495-1501), swine (Yi et al. 1996 J. Anim. Sci. 74:1601-1611; Leytem and Thacker 2008 J. Anim. Vet. Advan. 7:113-120), sheep (Leytem et al. 2007 An. Feed. Sci. Technol. 138:13-28) and dairy (Toor et al., 2005 J. Environ. Qual. 34:1380-1391; McDowell et al. 2008 J. Environ. Qual. 37:741-752; He et al. 2009 J. Environ. Qual. 38:1909-1918). Storage conditions, length of storage and amendments during storage, including additives such as phytase or alum will also affect manure P forms and their availability (e.g. Dao et al. 2001 J. Environ. Qual. 30:1693-1698; Moore and Edwards 2007 J. Environ. Qual. 36:163-174; Warren et al. 2008 J. Environ. Qual. 37:469-476; Hill and Cade-Menun 2009 J. Environ. Qual. 38:130-138; Casteel et al. 2011 Poult. Sci. 90:2689-2696; Peirce et al. 2013 Plant Soil 373:359-372; Huang et al. 2018 J. Environ. Qual. 47:345-352).
The authors have provided very limited information about the manures used in this study, beyond the amount of each fertilizer added (Table 1) and some very bad NMR spectra in the supplemental materials. They have not even included P pools from sequential fractionation (Table 2) for the fertilizers. This is not enough. They must include more detailed descriptions of the sources of these manures, including: feed, storage and treatments of manure (if any) during storage; concentrations of agronomically-relevant nutrients and N and P pools in these manures (e.g. Olsen P or other soil test P values; nitrate, ammonium or other soil test N values); total organic P; pH, exchangeable cations, etc.
Without detailed information about the organic fertilizers, it is difficult to extrapolate the results of this study to other manures; instead, the results become specific only to these particular fertilizers in these particular soils. And that is not very relevant scientifically, and will not be of interest to other readers of this journal.
4. The main method for soil P pools was a modified version of the Hedley fractionation method, which the authors used for soils only. Sequential P fraction is a common technique that is widely used. However, this is mainly because it is a simple, inexpensive method, rather than because it is chemically precise. All fractionation methods are operationally-defined, meaning that they are defined by the extractants used and the steps in the fractionation method (the order in which each extractant is used). Most extractants used are not specific for any particular P compounds, with the result that the method yields little meaningful data about specific soil P chemistry, as has been discussed for decades, and which has been demonstrated by comparing fractionation results to those from more advanced techniques such as P k-edge XANES (x-ray adsorption near edge structure) spectroscopy (e.g. Saunders 1959. Nature 4704:2037; Condron and Newman 2011 J. Soil Sediments 11: 830-840; Kar et al. 2011 Soil Sci. 176:589-595; Klotzbücher et al., 2019. J. Plant Nutr. Soil Sci. 182:570-577; Barrow et al., 2021 Plant Soil 459:1-11; Gu and Marginot 2021 Plant Soil 459:13-17).
4a. The authors used a very long extraction procedure, with many of the steps requiring 16 hours of extraction (Fig. S1). However, they do not indicate that they added anti-microbial agents (e.g. toluene, sodium azide). With long extractions such as this, microbial growth can transform P within the samples, either by mineralization of organic P species or by uptake and conversion of phosphate to complex inorganic P forms (e.g. polyphosphates) or organic P forms such as phospholipids or DNA. How certain are the authors that the fractionation results reflect P in the soil samples, and not transformations during the fractionation method?
4b. I am pleased to see that the authors have not labelled the fractions with any specific chemical terms. However, I am concerned that the authors have interpreted changes in these soil fraction as “transformations”(e.g., lines 28, 236, 346). The authors do not provide any information about the fractions in the fertilizers themselves. In my opinion, all the changes they see after incubations reflect the properties of the fertilizers added. If the authors genuinely want to show transformations of soil during the incubation experiment, then they need to provide data for the fertilizer materials and for the soil samples immediately after the fertilizers were added, in addition to data after 70 days of incubations.
4c. I am concerned about the authors’ determination of organic P in their fractions. First, the methods described in lines 138-142 describe the measurement of phosphate colorimetrically in each fraction before and after digestion. The authors are correct that the measurement after digestion is total P (TP) in each extract. However, the colorimetric measurement before digestion is not total inorganic P, but is merely the phosphate that can react with the color reagent (molybdate-reactive P, MRP). Thus, the difference between TP and MRP is not organic P, but is molybdate-unreactive P (MUP), which can include complex inorganic P compounds such as pyrophosphate.
5. A second main method used to characterize P in these samples was 31P nuclear magnetic resonance spectroscopy (P-NMR). The spectra shown in Figs. 4 and S2 are very pool quality. There are also problems with the identification of peaks in these samples. For example, the authors indicate “inositol hexaphosphate” for a general region of the spectra, labelled “C”, rather than identifying any individual peaks. There are several stereoisomers of inositol hexakisphosphates that can be present in spectra of soil extracts, each with multiple peaks that must be identified to confirm the presence of these compounds in samples. In addition, the broad region of the spectra labelled as “C” can contain a number of other compounds, products of diester degradation during sample extraction and analysis. Any peak identification requires spiking samples with known P compounds after the initial P-NMR analysis, and then reanalyzing the samples by P-NMR to confirm peak identifications. If the authors did this, then they need to show the results of these spiking experiments to confirm their peak identifications. If they did not conduct spiking experiments, then they need to do so in order for these P-NMR results to be publishable in any scientific journal.
6. I am also concerned by the authors’ correlation results in Fig. S4. Only independent variables should be correlated with each other. Methods such as NMR and sequential fractionation produce auto-correlated results, not independent variables: NMR because the results are determined as relative proportions, and P fractionation because each fractionation will depend on what is extracted in the previous fraction. Thus, many of the correlation results in Fig. S4 are meaningless because they are not all for independent variables. I am also concerned about the use of structural equation modelling (SEM) to draw conclusions about factors influencing P cycling in these soils, because SEM is merely a fancy method of correlation, and so is governed by the same rules as for simple correlations (e.g., using independent variables), and because I have concerned about the results in general (see previous points).
7. References: there are a number of problems with the references in this manuscript.
7a. The number of references cited is out of proportion to the length of the paper: the total length of the manuscript (including abstract and conclusions) is 326 lines, while the References is 220 lines. The authors should carefully check each reference to see if it is necessary.
7b. There are problems with many of the listings in the References. For example, “Gerard and Frederic” (lines 424-425) and “Gérard” (lines 426-427) are the same reference. The author’s name is Frederic Gérard, which the authors somehow split into to different authors. Unfortunately, they cite both of these in the text (lines 301-302). There are also problems with other references (e.g. Jiang et al. 2012.
8. There are problems with editing and quality of English through the text (e.g., “The relative contents of inorganic and organic P in soil is greatly” should be “The relative contents of inorganic and organic P in soil are greatly”, because the verb modifies “contents”. The authors need to carefully edit any revised manuscript.
Citation: https://doi.org/10.5194/soil-2021-127-RC1 -
AC1: 'Reply on RC1', Yuan Wang, 16 Mar 2022
Dear reviewer,
We greatly appreciate your time and expertise in reviewing our manuscript (soil-2021-127). We have carefully modified the manuscript based on your constructive comments, which significantly improve the manuscript. Appended is our point-by-point response to the comments. The detailed information is as follows:
1. This manuscript presents the results of a very simple study: the authors added four fertilizers developed from recycled waste materials, plus a chemical P fertilizer and a check with no fertilizer, to two soils and incubated them for 70 days. They monitored soil test (Olsen) P regularly over the 70-day incubation but did more detailed analyses on samples incubated for the full 70 days only. However, as the authors themselves point out in the Introduction and the Discussion, incubation studies with organic P sources such as manures are very common, and the majority of the conclusions of this study (e.g., “different P sources had different effects on soil P availability”, “soil Olsen-P content was mainly affected by the labile P fraction”, etc.) have been shown many times before. Therefore, while the results may be useful in the region where this study was conducted, the overall novelty is low as currently written. If this manuscript is revised, the authors must clearly indicate the factors that make this study different from previous studies, including novel results not shown by any previous study.
Thanks for your nice suggestions. Based on the comments, we have conducted a detailed revision in the Introduction. The main objective of this study is to provide a basis for the closed- P cycle in farming systems by recovering P from agricultural wastes. We attempted to explore promising renewable P-containing materials for achieving a closed cycle of P by understanding the transformation dynamics of different renewable P-containing materials in soil and their P availability. The soil texture and physicochemical properties such as pH and organic matter determined the P sorption reaction (Xiong et al., 2022; Debicka et al., 2016; Bouray et al., 2021). Quantifying the transformations of different phosphorus-containing materials in soils with different soil conditions is necessary to enhance phosphorus utilization and reduce phosphorus resource limitation. We have supplemented this background in the introduction.
To understand the transformation dynamics of different P-containing materials in the soil, we measured the P fractions of the initial soil, four renewable P-containing materials, and two soils with different P-containing materials on days 0,35, and 70 of incubation. The P fractions were not significantly different on day 70 of incubation compared to day 0 of incubation. Therefore, we analyzed the data from day 70 of incubation in the manuscript. However, we did not realize that these data are indispensable to understanding the mechanisms of transformation of different P-containing materials in two soils. The analysis and discussion of these data have been supplemented in the modified manuscript. We believe that this study is helpful and meaningful for understanding the mechanisms of P-containing material transformation in different soils.
And the conclusions were modified as follows: Compared with other renewable P-containing materials, CM is a superior source for improving soil P availability in fluvo-aquic and red soils. Compared to fluvo-aquic soil, phosphorus from SSP, PM, and CM was more strongly immobilized in red soil. Further analysis of the P fraction of two soils with different P-containing materials at days 0,35 and 70 of incubation revealed that the distribution of CM to the soil labile P fraction was significantly increased compared to other renewable P-containing materials. And compared with fluvo-aquic soil, the contribution of different P-containing materials to the labile P fraction of red soil was significantly decreased. Changes in P fractions at different incubation periods in soils with different P-containing materials show that most soil P fractions have no significant difference on day 70 of incubation compared to day 0 of incubation. That suggests, in the short term, the difference of potential bioavailability of P from various sources is determined by the distribution to soil labile P fractions rather than its transformation in the soil. In general, there is promising potential to reduce P limitation by recovering cattle manure as an alternative source of P supply. This study provides a basis for closing the P cycle in agricultural systems and for sustainable on-farm P management strategies.
2. One major concern is the lack of detailed information about the soils used in this study. The authors describe them as “calcareous fluvo-aquic soil in Quzhou” and “red soil in Shilin County” (line 108), and include very limited information about these soils in lines 109-113”. However, in the discussion, they make statements indicating that they view the results of this study to be widely applicable (e.g. “suggests that the application of bone meal in red soil”, lines 273-273; “adding maize straw and cattle bone meal to fluvo-aquic soil”, line 297). The authors need to provide a lot more information about these soils to demonstrate that the results of this study can be more widely applied than just the soils used in this study.
Thanks for pointing this out. The transformation process of P in soil is closely related to soil properties. Therefore, we selected two typical soils with different textures and pH for analysis. We have supplemented the details of these two soils in the materials and methods, to provide a reference for the wider application of this study. The modified as follows: Soil samples were collected from fluvo-aquic soil (calcareous alluvial soil) in Hebei Province and red soil (ultisol) in Yunnan Province. The soil texture of fluvo-aquic soil is silt loam soil with 7.9% of clay (<2 μm), 55.3% of silt (2–20 μm), and 36.8% of sand (20–2,000 μm). The soil texture of red soil is clay with 47.5% of clay (<2 μm), 25.3% of silt (2–20 μm), and 27.2% of sand (20–2,000 μm).
3. Another concern, related to the previous point, is the incomplete descriptions of the recycled P materials used in this study. The authors seem to assume that “poultry manure”, “cattle manure”, “maize straw” and “cattle bone powder” are adequate descriptions, despite indicating in the introduction that these materials can vary in composition (lines 65-70). based on the literature cited in lines 79-82. However, it is well-established in the literature that this is not true, especially for manure P. Many things will influence P forms and their cycling in manures even within the same species, including diet, animal age and life stage, animal bedding that may be included with animal feces, and storage and treatment of the manures before adding to soils. Diet formulations, including high or low concentrations of dietary P and the addition of phytase, has shown to strongly affect P species and concentrations in manure, including for poultry (Maguire et al. 2004 J. Environ. Qual. 33:2306-2316; McGrath et al. 2005 J. Environ. Qual. 34:1896-1909; Leytem et al. 2007 J. Sci. Food Agric. 87:1495-1501), swine (Yi et al. 1996 J. Anim. Sci. 74:1601-1611; Leytem and Thacker 2008 J. Anim. Vet. Advan. 7:113-120), sheep (Leytem et al. 2007 An. Feed. Sci. Technol. 138:13-28) and dairy (Toor et al., 2005 J. Environ. Qual. 34:1380-1391; McDowell et al. 2008 J. Environ. Qual. 37:741-752; He et al. 2009 J. Environ. Qual. 38:1909-1918). Storage conditions, length of storage, and amendments during storage, including additives such as phytase or alum, will also affect manure P forms and their availability (e.g. Dao et al. 2001 J. Environ. Qual. 30:1693-1698; Moore and Edwards 2007 J. Environ. Qual. 36:163-174; Warren et al. 2008 J. Environ. Qual. 37:469-476; Hill and Cade-Menu 2009 J. Environ. Qual. 38:130-138; Casteel et al. 2011 Poult. Sci. 90:2689-2696; Peirce et al. 2013 Plant Soil 373:359-372; Huang et al. 2018 J. Environ. Qual. 47:345-352). The authors have provided very limited information about the manures used in this study, beyond the amount of each fertilizer added (Table 1) and some very bad NMR spectra in the supplemental materials. They have not even included P pools from sequential fractionation (Table 2) for the fertilizers. This is not enough. They must include more detailed descriptions of the sources of these manures, including feed, storage, and treatments of manure (if any) during storage; concentrations of agronomically-relevant nutrients, and N and P pools in these manures (e.g. Olsen P or other soil test P values; nitrate, ammonium or other soil test N values); total organic P; pH, exchangeable cations, etc. Without detailed information about the organic fertilizers, it is difficult to extrapolate the results of this study to other manures; instead, the results become specific only to these particular fertilizers in these particular soils. And that is not very relevant scientifically, and will not be of interest to other readers of this journal.
Good suggestion. We have analyzed the basic properties of different P-containing materials including P fractions before the experiment, and the specific information about the four renewable P-containing materials has been supplemented in the materials and methods. For specific data, please refer to the materials and methods and supplementary materials of the revised manuscripts.
As suggested by the reviewers, we have modified as follows: The phosphorus fractions in manure are dependent on various factors, including manure type, solid-liquid separation status, manure removal method, handling way and degree of decomposition, etc (Li et al., 2014; Pagliari and Laboski, 2013). Especially for manure type, the differences in the digestive system and feed composition of different animals cause large differences in phosphorus concentration and fractions in different manures (Garcia-Albacete et al., 2012; Freiberg et al., 2020). Meanwhile, straw turnover is usually applied directly to the soil in agricultural practice, and the P availability in straw requires in-depth analysis (Guan et al., 2020). The bone meal which can be recycled and used as a large amount of organic fertilizer in the future remains unclear in terms of P reuse (Ylivainio et al., 2008). Thus, it is necessary to identify and quantify P fractions from different P-containing materials and their distribution in soil P fractions to determine the potential bioavailability and the environmental impact of P from various sources.
4. The main method for soil P pools was a modified version of the Hedley fractionation method, which the authors used for soils only. Sequential P fraction is a common technique that is widely used. However, this is mainly because it is a simple, inexpensive method, rather than because it is chemically precise. All fractionation methods are operationally-defined, meaning that they are defined by the extractants used and the steps in the fractionation method (the order in which each extractant is used). Most extractants used are not specific for any particular P compounds, with the result that the method yields little meaningful data about specific soil P chemistry, as has been discussed for decades, and which has been demonstrated by comparing fractionation results to those from more advanced techniques such as P K-edge XANES (x-ray absorption near edge structure) spectroscopy (e.g. Saunders 1959. Nature 4704:2037; Condron and Newman 2011 J. Soil Sediments 11: 830-840; Kar et al. 2011 Soil Sci. 176:589-595; Klotzbücher et al., 2019. J. Plant Nutr. Soil Sci. 182:570-577; Barrow et al., 2021 Plant Soil 459:1-11; Gu and Marginot 2021 Plant Soil 459:13-17).
We agree with you that the new techniques such as P K-edge XANES is useful to understanding the soil P transformation progress, while it is difficult for us now due to the crowded monitoring. We will try the advanced techniques to improve our future work.
4a. The authors used a very long extraction procedure, with many of the steps requiring 16 hours of extraction (Fig. S1). However, they do not indicate that they added anti-microbial agents (e.g. toluene, sodium azide). With long extractions such as this, microbial growth can transform P within the samples, either by mineralization of organic P species or by uptake and conversion of phosphate to complex inorganic P forms (e.g. polyphosphates) or organic P forms such as phospholipids or DNA. How certain are the authors that the fractionation results reflect P in the soil samples and not transformations during the fractionation method?
Thanks for pointing out this important point. We strictly follow the improved P sequential fractionation method by Tiessen and Moir. We agree that microorganisms will have an impact on the transformation of P in the long-term extraction process. Therefore, we strictly managed to shake time, environmental temperature, and chromogenic time in the operation of the test. All samples were measured under the same conditions to minimize the effects of P transformation on the results during the extraction process.
4b. I am pleased to see that the authors have not labeled the fractions with any specific chemical terms. However, I am concerned that the authors have interpreted changes in these soil fractions as “transformations” (e.g., lines 28, 236, 346). The authors do not provide any information about the fractions in the fertilizers themselves. In my opinion, all the changes they see after incubations reflect the properties of the fertilizers added. If the authors genuinely want to show transformations of soil during the incubation experiment, then they need to provide data for the fertilizer materials and the soil samples immediately after the fertilizers were added, in addition to data after 70 days of incubations.
Thanks for the helpful suggestions. We have supplemented the data of soil P fractions on days 0 and 35 of incubation in the supplementary materials and supplemented the discussion of these results in the manuscript.
4c. I am concerned about the authors’ determination of organic P in their fractions. First, the methods described in lines 138-142 describe the measurement of phosphate colorimetrically in each fraction before and after digestion. The authors are correct that the measurement after digestion is total P (TP) in each extract. However, the colorimetric measurement before digestion is not total inorganic P but is merely the phosphate that can react with the color reagent (molybdate-reactive P, MRP). Thus, the difference between TP and MRP is not organic P but is molybdate-unreactive P (MUP), which can include complex inorganic P compounds such as pyrophosphate.
Thanks. We followed the improved P sequential fractionation method to classify different P fractions. The P fractions before and after digestion are divided into inorganic P and organic P. We agree with the reviewer's suggestion and annotate this point in the Materials and Methods section of the manuscript.
5. A second main method used to characterize P in these samples was 31P nuclear magnetic resonance spectroscopy (P-NMR). The spectra shown in Figs. 4 and S2 are of very poor quality. There are also problems with the identification of peaks in these samples. For example, the authors indicate “inositol hexaphosphate” for a general region of the spectra, labeled “C”, rather than identifying any individual peaks. There are several stereoisomers of inositol hexakisphosphates that can be present in spectra of soil extracts, each with multiple peaks that must be identified to confirm the presence of these compounds in samples. In addition, the broad region of the spectra labeled as “C” can contain several other compounds, products of diester degradation during sample extraction and analysis. Any peak identification requires spiking samples with known P compounds after the initial P-NMR analysis and then reanalyzing the samples by P-NMR to confirm peak identifications. If the authors did this, then they need to show the results of these spiking experiments to confirm their peak identifications. If they did not conduct spiking experiments, then they need to do so for these P-NMR results to be publishable in any scientific journal.
Thank you for pointing out this lack of detailed information. This information has been supplemented with the modified manuscript.
6. I am also concerned by the authors’ correlation results in Fig. S4. Only independent variables should be correlated with each other. Methods such as NMR and sequential fractionation produce auto-correlated results, not independent variables: NMR because the results are determined as relative proportions, and P fractionation because each fractionation will depend on what is extracted in the previous fraction. Thus, many of the correlation results in Fig. S4 are meaningless because they are not all for independent variables. I am also concerned about the use of structural equation modeling (SEM) to conclude factors influencing P cycling in these soils, because SEM is merely a fancy method of correlation, and so is governed by the same rules as for simple correlations (e.g., using independent variables), and because I have concerned about the results in general (see previous points).
Thanks for the helpful suggestions. We modified the graphical representation of the correlation between Olsen-P and P fractions in the supplementary materials. Please refer to supplementary material figure S4 for specific modifications. Structural equation modeling (SEM) can intuitively show the complex path relationship. SEM is also widely used in the study of the soil P cycle (Hou et al., 2016; Costa et al., 2016; Qaswar et al., 2020). In this study, SEM helps us to better understand the process and environmental factors driving soil P transformation. We have redescribed the SEM results in the modified manuscript.
7. References: there are several problems with the references in this manuscript.
7a. The number of references cited is out of proportion to the length of the paper: the total length of the manuscript (including abstract and conclusions) is 326 lines, while the References is 220 lines. The authors should carefully check each reference to see if it is necessary.
We have updated the references accordingly.
7b. There are problems with many of the listings in the References. For example, “Gerard and Frederic” (lines 424-425) and “Gérard” (lines 426-427) are the same references. The author’s name is Frederic Gérard, which the authors somehow split into two different authors. Unfortunately, they cite both of these in the text (lines 301-302). There are also problems with other references (e.g. Jiang et al. 2012.
Thank you for pointing this out. We have updated the references accordingly.
8. There are problems with editing and quality of English through the text (e.g., “The relative contents of inorganic and organic P in soil is great” should be “The relative contents of inorganic and organic P in soil are great” because the verb modifies “contents”. The authors need to carefully edit any revised manuscript.
We would like to express our heartfelt thanks to the reviewer for the thorough reading of our manuscript and the very useful suggestions. We carefully considered the reviewers' suggestions and made corresponding modifications, which greatly improved our manuscript. During the revision process, we have also done very careful language polishing accordingly.
References of response to referee comments
Bouray, M., Moir, J. L., Lehto, N. J., Condron, L. M., Touhami, D., and Hummel, C.: Soil pH effects on phosphorus mobilization in the rhizosphere of Lupinus angustifolius, Plant and Soil, 469, 387-407, https://doi.org/10.1007/s11104-021-05177-4, 2021.
Costa, M. G., Gama-Rodrigues, A. C., Goncalves, J. L. D., Gama-Rodrigues, E. F., Sales, M. V. D., and Aleixo, S.: Labile and Non-Labile Fractions of Phosphorus and Its Transformations in Soil under Eucalyptus Plantations, Brazil, Forests, 7, https://doi.org/10.3390/f7010015, 2016.
Debicka, M., Kocowicz, A., Weber, J., and Jamroz, E.: Organic matter effects on phosphorus sorption in sandy soils, Archives of Agronomy and Soil Science, 62, 840-855, https://doi.org/10.1080/03650340.2015.1083981, 2016.
Freiberg, Y., Fine, P., Levkovitch, I., and Baram, S.: Effects of the origins and stabilization of biosolids and biowastes on their phosphorous composition and extractability, Waste Management, 113, 145-153, https://doi.org/10.1016/j.wasman.2020.06.002, 2020.
Garcia-Albacete, M., Martin, A., and Cartagena, M. C.: Fractionation of phosphorus biowastes: Characterisation and environmental risk, Waste Management, 32, 1061-1068, https://doi.org/10.1016/j.wasman.2012.02.003, 2012.
Guan, X. K., Wei, L., Turner, N. C., Ma, S. C., Yang, M., and Wang, T. C.: Improved straw management practices promote in situ straw decomposition and nutrient release and increase crop production, Journal of Cleaner Production, 250, 119514.119511-119514.119513, 2020.
Hou, E. Q., Chen, C. R., Kuang, Y. W., Zhang, Y. G., Heenan, M., and Wen, D. Z.: A structural equation model analysis of phosphorus transformations in global unfertilized and uncultivated soils, Global Biogeochemical Cycles, 30, 1300-1309, https://doi.org/10.1002/2016gb005371, 2016.
Li, G., Li, H., Leffelaar, P. A., Shen, J., and Zhang, F.: Characterization of phosphorus in animal manures collected from three (dairy, swine, and broiler) farms in China, PLoS One, 9, e102698, https://doi.org/10.1371/journal.pone.0102698, 2014.
Pagliari, P. H. and Laboski, C. A. M.: Dairy manure treatment effects on manure phosphorus fractionation and changes in soil test phosphorus, Biology and Fertility of Soils, 49, 987-999, https://doi.org/10.1007/s00374-013-0798-2, 2013.
Qaswar, M., Chai, R. S., Ahmed, W., Jing, H., Han, T. F., Liu, K. L., Ye, X. X., Xu, Y. M., Anthonio, C. K., and Zhang, H. M.: Partial substitution of chemical fertilizers with organic amendments increased rice yield by changing phosphorus fractions and improving phosphatase activities in fluvo-aquic soil, Journal of Soils and Sediments, 20, 1285-1296, https://doi.org/10.1007/s11368-019-02476-3, 2020.
Xiong, J., Liu, Z. H., Yan, Y. P., Xu, J. L., Liu, D., Tan, W. F., and Feng, X. H.: Role of clay minerals in controlling phosphorus availability in a subtropical Alfisol, Geoderma, 409, https://doi.org/10.1016/j.geoderma.2021.115592, 2022.
Ylivainio, K., Uusitalo, R., and Turtola, E.: Meat bone meal and fox manure as P sources for ryegrass (Lolium multiflorum) grown on a limed soil, Nutrient Cycling in Agroecosystems, 81, 267-278, https://doi.org/10.1007/s10705-007-9162-y, 2008.
Citation: https://doi.org/10.5194/soil-2021-127-AC1
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AC1: 'Reply on RC1', Yuan Wang, 16 Mar 2022
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CC1: 'Comment on soil-2021-127', Peter Leinweber, 05 Jan 2022
- 1
- 27: The manures and maize straw are P-containing materials but not P fertilizers, sensu stricto.
- 37: Overall, the concluding sentence is very general. Reader in fact remains uninformed, what is novel in this study. No explanation is given for the descriptive findings. For instance, cattle manure performed best but what is the "considerable practical significance" of this finding in P-recycling? ... Using all cattle manure as soil amendments = done anyway; raising more cattle ...? Or, is this an overall meaningless phrase? Authors are vague in their conclusions or remain almost unclear.
- 2
INTRO
l. 46: What in detail are "the attendant ... quality issues"? Vague expression, meaningless if no more details are given.- 64/65: For increases and decreases explained here, different bases were used (proportions vs. contents). Thus, meaning of this statement is unclear. In fact, proportions cannot directly compared with contents/concentrations.
- 3
- 66-69: This literature evaluation is incomplete and rather selective. For sure, much more is known about P in manures and similar materials. All this should have been compiled to disclose real knowledge gaps and lay a basis for the present study. Here it reads rather vague, like "effects are complex and need to be studied". That is not a strong rationale for a laborious scientific study.
- 63-74: Again, references are very incomplete. Much more is known, even on the soil the authors mention at l. 75, 76.
- 73: "contents ... are influenced ...".
- 74-76: Weak conclusive rationale for study. What is meant with “edaphic conditions"?
- 76: "Hedley fractionation" is slang. It is a sequential P fractionation after Hedley et al., modified by Tiessen .... It is a division of total soil P into fractions, not fractions into fractions. Imprecise explanation.
- 78/79: This reference refers to "a subtropical region". For evidencing "wide use" some review articles should have been cited at least (I recommend reading first Cross & Schlesinger).
- 79-82: 2 contrasting statements in 1 sentence but references are not assigned to each of the statements. Unclear for reader....
- 83 ff. As already criticized above for the P fractionation, literature review of 31P NMR is very selective and fragmentary. For instance, not any study of P in manures and other P recycling materials has been mentioned although many of such studies have been published.
4:
l 96: When introducing the soils, authors should use internationally understandable soil units, like the WRB system. "Red" indicates Ferralsols or ferralic subunits of other Major Soil Units, developed from intensive weathering under subtropical/tropical climate conditions. By contrast to this system "Red" as such is not an internationally accepted soil classification; same with "fluvo-aquic" (if not in combination with a WRB unit). This imprecision is hard to understand, considering that the WRB System and secondary literature on it refer to the P issues in great detail.
- 97: "Little is known" is a phrase very often used, but this phrase is meaningless if authors do not communicate what in detail (even if it is not much) is known (… and what is unknown but important to know).
- 100-103: Authors write what they did but they do not report what they intended to find out or what their research hypotheses were. Overall, my impression of the INTRO text is "vague", "not very well reviewed" and "immature" in how the rationale for study was tried to develop.
- MATERIALS & METHODS:
Soil materials should be described in terms of WRB units and soil horizon origin. Instead of "Olsen" the detailed extractant should be given.
- 116-117: This is confusing; better assign the concentrations to each of the materials.
p. 5: - 138-142: Unclear how Pt and Pi were determined if Po is the difference Pt-Pi? Description should be clear and understandable without checking the Figure S1.
l 143: variation? I do think that 31P NMR can quantify species. - 148 ... contains incomplete sentence
RESULTS
l. 176: First of all, I see in Fig. 1, that the differences which appear at the end of incubation are more or less already obvious at the starting point. That indicates that the results reflect inherent properties of the materials added, rather than - or in addition to – the interactions with soil particles. Therefore, the study is incomplete without giving the analyses results for the non-amended soils (maybe controls) and amendments (prior to addition to soil). Study would gain scientific value if the authors would be able to distinguish between effects of materials composition and interaction with soil (the latter leading to differences between soils (… for which details of mineralogy must be known).
l. 180 ff: Differences between treaments better should be explained as factors. Data as percent bear the risk of confusion if basis for calculation is unclear.
l. 177: Olsen P cannot be "improved". This is bad slang. The concentration of NaHCO3-extracted be can be increased by factor of ... (= more precise explanation)- 179-180: Bad wording; better assign factor of increase to each treatment.
Sorry authors, here I stop reading/revising your manuscript. In my view, it is too immature to be seriously reviewed. As a reviewer, I feel wasting my time with your text. A greatly improved version, developed and written with much more care, should be submitted which starts with thorough revision of the pertinent literature, logical deriving knowledge gaps and rationales for study, and testable hypotheses.
>>>> Finally, just a quick jump to the final section >>>>
CONCLUSIONS
l. 339: This is not new but has been shown in many previous studies.
l. 340-348: None of this is conclusion but almost all repetition of previous text. Reader cannot find any original new information from this section.l: 343-344: This is not surprising but could be expected because of same extractant (weak NaHCO3-solution) in sequential extraction and the so-called Olsen-method. As such, it is a meaningless result.
Citation: https://doi.org/10.5194/soil-2021-127-CC1 -
AC3: 'Reply on CC1', Yuan Wang, 16 Mar 2022
Dear Dr. Leinweber,
We greatly appreciate your time and expertise in reviewing our manuscript (soil-2021-127). We have carefully modified the manuscript based on your constructive comments, which significantly improve the manuscript. Appended is our point-by-point response to the comments. The detailed information is as follows:
1. 27: The manures and maize straw are P-containing materials but not P fertilizers, sensu stricto.
Thanks for the nice suggestion. We agree with you and have modified this expression throughout the text.
37: Overall, the concluding sentence is very general. Reader in fact remains uninformed, which is novel in this study. No explanation is given for the descriptive findings. For instance, cattle manure performed best but what is the "considerable practical significance" of this finding in P-recycling? ... Using all cattle manure as soil amendments = done anyway; raising more cattle ...? Or, is this an overall meaningless phrase? Authors are vague in their conclusions or remain almost unclear.
Thanks. Based on your suggestion we have significantly revised the conclusions and highlighted our main findings.
46: What in detail are "the attendant ... quality issues"? Vague expression, meaningless if no more details are given.
Thanks. We have corrected this sentence in the modified manuscript. A modified version is shown as follows: excessive application of phosphate fertilizer is a common phenomenon, which leads to soil P accumulation, water pollution, and crop quality decline.
64/65: For increases and decreases explained here, different bases were used (proportions vs. contents). Thus, the meaning of this statement is unclear. Proportions cannot be directly compared with contents/concentrations.
Thanks. Based on the comments We revise the sentence as follows: Also, application of organic fertilizer increased the proportion of labile organic phosphate (Po) and inositol hexaphosphate (IHP) but decreased stable Ca-associated P proportion.
66-69: This literature evaluation is incomplete and rather selective. For sure, much more is known about P in manures and similar materials. All this should have been compiled to disclose real knowledge gaps and lay a basis for the present study. Here it reads rather vague, like "effects are complex and need to be studied". That is not a strong rationale for a laborious scientific study.
Thanks. As suggested by the reviewers, we have deleted the first sentence and revised the sentence as follows: The P fractions in manure are dependent on various factors, including manure type, solid-liquid separation status, manure removal method, handling way and degree of decomposition, etc (Li et al., 2014a; Pagliari and Laboski, 2013). Especially for manure type, the differences in the digestive system and feed composition of different animals cause large differences in P concentration and fractions in different manures (Garcia-Albacete et al., 2012; Freiberg et al., 2020). Meanwhile, straw turnover is usually applied directly to the soil in agricultural practice, and the P availability in straw requires in-depth analysis (Guan et al., 2020). The bone meal which can be recycled and used as a large amount of organic fertilizer in the future remains unclear in terms of P reuse (Ylivainio et al., 2008). Thus, it is necessary to identify and quantify P fractions from different P-containing materials and their distribution in soil P fractions to determine the potential bioavailability of P from various sources.
63-74: Again, references are very incomplete. Much more is known, even on the soil, the authors mention at l. 75, 76.
As suggested by the reviewers, we have supplemented relevant information in the Introduction section.
73: "contents ... are influenced ...".
Thanks. The initial description has been modified as follows: the relative contents of inorganic and organic P in soil were greatly affected by soil type, land use and the type of organic amendment applied.
74-76: Weak conclusive rationale for the study. What is meant by “edaphic conditions"?
Thank you for your suggestion. We modified the sentence as follows: it is valuable to reveal the transformation mechanism of different P-containing materials in soil and its relationship with soil properties by studying the difference of P fractions in a typical red soil (low pH) and a fluvo-aquic soil (slightly alkaline pH) with different P-containing materials.
76: "Hedley fractionation" is slang. It is a sequential P fractionation after Hedley et al., modified by Tiessen… It is a division of total soil P into fractions, not fractions into fractions. Imprecise explanation.
Thanks. We modified the sentence accordingly.
78/79: This reference refers to "a subtropical region". For evidencing "wide use" some review articles should have been cited at least (I recommend reading first Cross & Schlesinger).
Thank you for the suggestion. We have supplemented the references related to P fractions in other research regions.
79-82: 2 contrasting statements in 1 sentence but references are not assigned to each of the statements. Unclear for the reader…
Thank you. The reference has been modified.
83 ff. As already criticized above for the P fractionation, the literature review of 31P NMR is very selective and fragmentary. For instance, not any study of P in manures and other P recycling materials has been mentioned although many of such studies have been published.
Thank you for the comments. We have supplemented the relevant studies as follows: Previous studies reported that the solution 31P-NMR procedure detected more phytic acid in poultry manure than that in cattle manure (Li et al., 2014b; Jayasundera et al., 2005).
96: When introducing the soils, authors should use internationally understandable soil units, like the WRB system. "Red" indicates Ferralsols or ferric subunits of other Major Soil Units, developed from intensive weathering under subtropical/tropical climate conditions. By contrast to this system, "Red" as such is not an internationally accepted soil classification; same with "fluvo-aquic" (if not in combination with a WRB unit). This imprecision is hard to understand, considering that the WRB System and secondary literature on it refer to the P issues in great detail.
We agree with these comments. We have supplemented the details of these two soils in the materials and methods, to provide a reference for the wider application of this study. The modified as follows: Soil samples were collected from fluvo-aquic soil (calcareous alluvial soil) in Hebei Province and red soil (ultisol) in Yunnan Province. The soil texture of fluvo-aquic soil is silt loam soil with 7.9% of clay (<2 μm), 55.3% of silt (2–20 μm), and 36.8% of sand (20–2,000 μm). The soil texture of red soil is clay with 47.5% of clay (<2 μm), 25.3% of silt (2–20 μm), and 27.2% of sand (20–2,000 μm).
97: "Little is known" is a phrase very often used, but this phrase is meaningless if authors do not communicate what in detail (even if it is not much) is known (and what is unknown but important to know).
Thank you for pointing this out. We have modified it as follows: quantifying the variation of soil P availability on the time scale and in different soil types (representative of acidic and alkaline soils) is worth further investigation.
100-103: Authors write what they did but they do not report what they intended to find out or what their research hypotheses were. Overall, my impression of the INTRO text is "vague", "not very well-reviewed" and "immature" in how the rationale for the study was tried to develop.
We would like to thank the reviewer for her critical and constructive comments. The research objectives and hypothesis has been redrafted at the end of the introduction section. We hypothesized that：(1) Compared with MS, CB, and PM, CM is more efficient renewable P-containing materials. (2) Compared with fluvo-aquic soil, different P-containing materials are more easily fixed in red soil. (3) The difference in potential bioavailability of P from various sources is determined by their distribution to soil labile P fractions.
2. MATERIALS & METHODS:
Soil materials should be described in terms of WRB units and soil horizon origin. Instead of "Olsen" the detailed extractant should be given.
Thanks for the constructive comments. We have supplemented the material methods section with more details on soil properties and Olsen-P extractant.
116-117: This is confusing; better assign the concentrations to each of the materials.
Apologies for this confusing information. We have modified this accordingly.
138-142: Unclear how Pt and Pi were determined if Po is the difference Pt-Pi? The description should be clear and understandable without checking Figure S1.
Thank you for your suggestion. We have modified it as follows: The concentration of Po is equal to the concentration of total P (Pt) minus the concentration of inorganic P (Pi).
143: variation? I do think that 31P NMR can quantify species.
Thank you for your suggestion. The title has been modified.
148: contains the incomplete sentence
Thank you for pointing this out. The sentence has been modified as follows: the solution pH was adjusted to 9.0±1.0, kept steady for 30 min, and again centrifuged at 12000 g (20 ℃) for 30 minutes.
3. 176: First of all, I see in Fig. 1, that the differences which appear at the end of incubation are more or less already obvious at the starting point. That indicates that the results reflect inherent properties of the materials added, rather than - or in addition to – the interactions with soil particles. Therefore, the study is incomplete without giving the analyses results for the non-amended soils (maybe controls) and amendments (prior to addition to soil). The study would gain scientific value if the authors would be able to distinguish between effects of materials composition and interaction with soil (the latter leading to differences between soils (… for which details of mineralogy must be known).
Thank you for these valuable comments. The analysis and discussion of these data have been supplemented in the modified manuscript accordingly.
180 ff: Differences between treatments better should be explained as factors. Data as percent bear the risk of confusion if the basis for calculation is unclear.
Thank you for your suggestion. The expression has been modified as follows: During 0-70 days of incubation, the Olsen-P concentration of SSP, PM and CM enriched fluvo-aquic soil has increased by 49.5 mg·kg-1, 21.7 mg·kg-1, and 34.4 mg·kg-1 compared with CK in average, respectively. In SSP, PM, and CM enriched red soil, the Olsen-P concentration was increased by 29.9 mg·kg-1 15.3 mg·kg-1 and 23.8 mg·kg-1 compared with CK on average during 0-70 days of incubation, respectively. CM outperformed other renewable P-containing materials in increasing Olsen-P concentration. In fluvo-aquic soil, the Olsen-P concentration of soil with CM was significantly increased by 12.7 mg·kg-1, 34.5 mg·kg-1, and 34.24 mg·kg-1 on average compared with PM, MS, and CB, respectively. In red soil, the Olsen-P concentration of soil with CM was significantly increased by 8.5 mg·kg-1, 25.3 mg·kg-1, and 19.4 mg·kg-1 on average compared with PM, MS, and CB, respectively.
177: Olsen P cannot be "improved". This is bad slang. The concentration of NaHCO3-extracted be can be increased by a factor of ... (= more precise explanation)
Thank you for pointing this out. The expression has been modified as follows: based on the effect size, treatments could be grouped into (1) those that significantly increased Olsen-P concentration and (2) those that slightly or insignificantly increased Olsen-P concentration, following soil enrichment with different P-containing materials.
179-180: Bad wording; better assign factor of increase to each treatment.
Thank you for pointing this out. We have modified it accordingly.
Sorry authors, here I stop reading/revising your manuscript. In my view, it is too immature to be seriously reviewed. As a reviewer, I feel wasting my time with your text. A greatly improved version, developed and written with much more care, should be submitted which starts with a thorough revision of the pertinent literature, logical deriving knowledge gaps and rationales for study, and testable hypotheses.
We sincerely accept these criticisms. The main objective of this study is to provide a basis for the closed- P cycle in farming systems by recovering P from agricultural wastes. We attempted to explore promising renewable P-containing materials for achieving a closed cycle of P by understanding the transformation dynamics of different renewable P-containing materials in soil and their P availability. The soil texture and physicochemical properties such as pH and organic matter determined the P sorption reaction (Xiong et al., 2022; Debicka et al., 2016; Bouray et al., 2021). Quantifying the transformations of different P-containing materials in soils with different soil conditions is necessary to enhance P utilization and reduce P resource limitation. We have supplemented this background in the introduction.
To understand the transformation dynamics of different P-containing materials in the soil, we measured the P fractions of the initial soil, four renewable P-containing materials, and two soils with different P-containing materials on days 0,35, and 70 of incubation. As mentioned by the reviewers, the differences which appear at the end of incubation are more or less already obvious at the starting point. The P fractions were not significantly different on day 70 of incubation compared to day 0 of incubation. Therefore, we analyzed the data from day 70 of incubation in manuscript. However, we did not realize that these data are indispensable to understanding the mechanisms of transformation of different P-containing materials in two soils. The analysis and discussion of these data have been supplemented in the modified manuscript. These comments have greatly improved our manuscript. We believe that this study is valuable and meaningful for understanding the mechanisms of P-containing material transformation in different soils.
4. CONCLUSIONS
339: This is not new but has been shown in many previous studies.
340-348: None of this is a conclusion but almost all repetition of the previous text. The reader cannot find any original new information from this section.
343-344: This is not surprising but could be expected because of the same extractant (weak NaHCO3-solution) in sequential extraction and the so-called Olsen method. As such, it is a meaningless result.
We express our sincere appreciation for your careful work and thoughtful suggestions. These comments were valuable and helpful in revising and improving the manuscript. The abstracts have been significantly revised and the conclusions have been rewritten.
The conclusions were modified as follows: Compared with other renewable P-containing materials, CM is a superior source for improving soil P availability in fluvo-aquic and red soils. Compared to fluvo-aquic soil, phosphorus from SSP, PM, and CM was more strongly immobilized in red soil. Further analysis of the P fraction of two soils with different P-containing materials at days 0,35 and 70 of incubation revealed that the distribution of CM to the soil labile P fraction was significantly increased compared to other renewable P-containing materials. And compared with fluvo-aquic soil, the contribution of different P-containing materials to the labile P fraction of red soil was significantly decreased. Changes in P fractions at different incubation periods in soils with different P-containing materials show that most soil P fractions have no significant difference on day 70 of incubation compared to day 0 of incubation. That suggests, in the short term, the difference of potential bioavailability of P from various sources is determined by the distribution to soil labile P fractions rather than its transformation in the soil. In general, there is promising potential to reduce P limitation by recovering cattle manure as an alternative source of P supply. This study provides a basis for closing the P cycle in agricultural systems and for sustainable on-farm P management strategies.
Thank you again for your suggestions and help, and we look forward to receiving your suggestions for our revised manuscript again.
References of response to referee comments
Bouray, M., Moir, J. L., Lehto, N. J., Condron, L. M., Touhami, D., and Hummel, C.: Soil pH effects on phosphorus mobilization in the rhizosphere of Lupinus angustifolius, Plant and Soil, 469, 387-407, https://doi.org/10.1007/s11104-021-05177-4, 2021.
Debicka, M., Kocowicz, A., Weber, J., and Jamroz, E.: Organic matter effects on phosphorus sorption in sandy soils, Archives of Agronomy and Soil Science, 62, 840-855, https://doi.org/10.1080/03650340.2015.1083981, 2016.
Freiberg, Y., Fine, P., Levkovitch, I., and Baram, S.: Effects of the origins and stabilization of biosolids and biowastes on their phosphorous composition and extractability, Waste Management, 113, 145-153, https://doi.org/10.1016/j.wasman.2020.06.002, 2020.
Garcia-Albacete, M., Martin, A., and Cartagena, M. C.: Fractionation of phosphorus biowastes: Characterisation and environmental risk, Waste Management, 32, 1061-1068, https://doi.org/10.1016/j.wasman.2012.02.003, 2012.
Guan, X. K., Wei, L., Turner, N. C., Ma, S. C., Yang, M., and Wang, T. C.: Improved straw management practices promote in situ straw decomposition and nutrient release and increase crop production, Journal of Cleaner Production, 250, 119514.119511-119514.119513, 2020.
Jayasundera, S., , W. F. S., III, J. B. R., and Dao, T. H.: Direct 31P NMR spectroscopic measurement of phosphorus forms in dairy manures, Journal of Food, Agriculture & Environment, 3, 5, 2005.
Li, G., Li, H., Leffelaar, P. A., Shen, J., and Zhang, F.: Characterization of phosphorus in animal manures collected from three (dairy, swine, and broiler) farms in China, PLoS One, 9, e102698, https://doi.org/10.1371/journal.pone.0102698, 2014a.
Li, G. H., Li, H. G., Leffelaar, P. A., Shen, J. B., and Zhang, F. S.: Characterization of Phosphorus in Animal Manures Collected from Three (Dairy, Swine, and Broiler) Farms in China, Plos One, 9, https://doi.org/10.1371/journal.pone.0102698, 2014b.
Pagliari, P. H. and Laboski, C. A. M.: Dairy manure treatment effects on manure phosphorus fractionation and changes in soil test phosphorus, Biology and Fertility of Soils, 49, 987-999, https://doi.org/10.1007/s00374-013-0798-2, 2013.
Xiong, J., Liu, Z. H., Yan, Y. P., Xu, J. L., Liu, D., Tan, W. F., and Feng, X. H.: Role of clay minerals in controlling phosphorus availability in a subtropical Alfisol, Geoderma, 409, https://doi.org/10.1016/j.geoderma.2021.115592, 2022.
Ylivainio, K., Uusitalo, R., and Turtola, E.: Meat bone meal and fox manure as P sources for ryegrass (Lolium multiflorum) grown on a limed soil, Nutrient Cycling in Agroecosystems, 81, 267-278, https://doi.org/10.1007/s10705-007-9162-y, 2008.
Citation: https://doi.org/10.5194/soil-2021-127-AC3
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RC2: 'Comment on soil-2021-127', Chiara Pistocchi, 14 Feb 2022
The manuscript of Wang and colleagues reports the effect of four organic amendments/fertilizers on phosphorus (P) pools in two different soils assessed through an incubation experiment. The soil P pools are investigated by sequential P fractionation and 31P solution nuclear magnetic resonance (NMR). The subject is relevant and timely as it deals with the recycling of P in order to reduce the use of mineral P fertilizers, which are produced from non-renewable resources. Although the manuscript is well structured and the experiment is well designed, some major points need to be addressed before publication. See specific comments.
Specific comments:
The main issue in my opinion is the lack of mechanistic interpretation of the reported findings. The effect of organic amendments or fertilizers on soil P has been investigate by several studies, see the non-exhaustive list of references reported below. The authors need to highlight better how their work allows advancing in the understanding of mechanisms driving P availability after the addition of organic amendments and what is the general interest of their research. This issue is also evident from the lack of scientific questions or hypotheses in the introduction, where only operational goals are reported (L98-103)
Motavalli, P., and R. Miles. "Soil phosphorus fractions after 111 years of animal manure and fertilizer applications." Biology and fertility of soils 36.1 (2002): 35-42.
Waldrip, Heidi M., Zhongqi He, and M. Susan Erich. "Effects of poultry manure amendment on phosphorus uptake by ryegrass, soil phosphorus fractions and phosphatase activity." Biology and Fertility of Soils 47.4 (2011): 407-418.
Halajnia, Akram, et al. "Phosphorus fractions in calcareous soils amended with P fertilizer and cattle manure." Geoderma 150.1-2 (2009): 209-213.
Kashem, Md Abul, Olalekan Oluwole Akinremi, and Geza Joseph Racz. "Phosphorus fractions in soil amended with organic and inorganic phosphorus sources." Canadian Journal of Soil Science 84.1 (2004): 83-90.
Brod, Eva, et al. "Waste products as alternative phosphorus fertilisers part I: inorganic P species affect fertilisation effects depending on soil pH." Nutrient Cycling in Agroecosystems 103.2 (2015): 167-185.
Brod, E., Øgaard, A.F., Haraldsen, T.K. et al. Waste products as alternative phosphorus fertilisers part II: predicting P fertilisation effects by chemical extraction. Nutr Cycl Agroecosyst 103, 187–199 (2015). https://doi.org/10.1007/s10705-015-9731-4
A second point is about the recycled fertilizer/amendment material: why these specific materials were chosen? For example, why including maize straw, which is commonly left in the field and therefore do not constitute an external P input? In addition, these materials are poorly characterized. The total NPK contents are not sufficient to characterize these materials as already pointed out by the first reviewer. Information concerning the repartition between inorganic and organic P as well as the water-soluble or bicarbonate-soluble P forms in the fertilizers should be provided. I wonder why the sequential extraction was not performed on these products. A more detailed characterization of the applied material would help a more mechanistic interpretation of the results. Additional variables, such as dissolved and total organic carbon in these products, would help interpret the results. Dissolved organic compounds, for example might displace some adsorbed phosphorus, thus increasing its availability. The discussion Section “Large variability for soil P availability…” would greatly benefit and be less speculative if a more detailed characterization of the organic materials was performed.
The third point concerns the data analysis and other soil variables. The Olsen P and labile P fractions from the sequential extraction are correlated in the structural equation model because the P extracted with these two procedures is largely the same (L232-234 and L343-344). For this reason, it is confusing to state that “the labile P fractions and the moderately labile P fractions had positive effects on soil Olsen P” (L232-233) and other similar expressions. To provide a more mechanistic understanding using the SEM, it would be useful to include independent soil variables, such as clay content, iron oxides content, soluble organic carbon (which is expected to vary with the addition of organic material), which are all known to influence the sorption/desorption reactions of P in soils and therefore its availability.
It is also not clear which data were used to build the SEM, i.e. corresponding to which time points of the incubation.
Finally, language editing is needed, paying attention also to terminology. For example, the P fractions are most of the time called labile/moderately labile etc., but sometimes the words “stable” or “active” or “inert” are used. This might create confusion, as these terms are not specifically defined. I suggest adopting a consistent terminology throughout the manuscript. Another point: according to their NPK content, some of the organic products, ex maize straw, are technically amendments and not fertilizers.
Minor comments:
Please check throughout the manuscript the numbers after the decimal point in the percentages (sometimes zero, sometimes one or two numbers are shown, ex line 181, line 200, line 206) and homogenise to significant precision.
L45-46: “the attendant environmental…” unclear formulation, please revise
L58: “it also affects” not clear what it refers to
L79-80: there are many papers published on the effect of organic fertilizers/amendments on soil P fractions (see the non-exhaustive list above). I suggest checking and integrating this literature into the introduction
L109-112: other properties of the two soils such as the mineralogy or at least the texture would be useful, as well as a classification of the soils such as according the international World Reference Base (WRB)
L117: please, specify whether the P and K concentration in the products are given as P2O5 and K2O or as P and K. It is always preferable to express them as P and K, see:
Lambers, Hans, and N. J. Barrow. "Pervasive use of P2O5, K2O, CaO, MgO, and basic cations, none of which exist in soil." Biology and Fertility of Soils 56.6 (2020): 743-745.
L127: please, specify to what the percent of soil moisture is referred to, e.g. water holding capacity or soil weight …
L122-123: what is the rationale of this quantity of P added?
L143: “quantitation” is rather “quantification”?
L184: what are these ranges referred to? Is that the time points?
L190: “soil P fractions” instead of “fractionations”
L191-192 and L214: does the P added was completely recovered in the extracted fractions or not? This information is not easy to infer from table 2 or figure 3 but it would be useful to verify how much of the added P was not accounted for in the sequential extraction end ended up into non-extractable P.
L225-226: “and more inositol… both soils” awkward formulation, please re-word
L226 “supplemented both soil”, please reformulate
L269: what “drab soil” means?
L279 “found rapid integration” please, reformulate this sentence
L307-310: please refer to the supplementary figure showing pH values.
L343-344: The P extracted with the Olsen extractant largely overlaps with the labile fractions of the sequential extraction. See also the third main point.
Tables and figures
Table 2: I am surprised by the very good precision of the measurements in some fractions, such as in the NaOH-Po, for which, in my experience, the variability usually is quite large. Are those analytical or real replicates?
Not all the figures in supplementary materials are referenced in the text
Citation: https://doi.org/10.5194/soil-2021-127-RC2 -
AC2: 'Reply on RC2', Yuan Wang, 16 Mar 2022
Dear Dr. Pistocchi,
We greatly appreciate your time and expertise in reviewing our manuscript (soil-2021-127). We have carefully modified the manuscript based on your constructive comments, which significantly improve the manuscript. Appended is our point-by-point response to the comments. The detailed information is as follows:
1. The main issue in my opinion is the lack of mechanistic interpretation of the reported findings. The effect of organic amendments or fertilizers on soil P has been investigated by several studies, see the non-exhaustive list of references reported below. The authors need to highlight better how their work allows advancing in the understanding of mechanisms driving P availability after the addition of organic amendments and what is the general interest of their research. This issue is also evident from the lack of scientific questions or hypotheses in the introduction, where only operational goals are reported (L98-103).
Good suggestion. The application of organic fertilizer in agriculture as a soil structure improvement and nitrogen source has been widely studied. While the problem of high environmental risk caused by a large amount of P in organic fertilizer is becoming more and more prominent. Therefore, this study focuses on the soil P transformation from different renewable P-containing materials and aims to quantify the variation of soil P availability on the time scale and in different soil types (representative of acidic and alkaline soils). Based on the suggestion, we supplement the scientific hypotheses in the Introduction as follows: We hypothesized that：(1) Compared with MS, CB, and PM, CM is more efficient renewable P-containing materials. (2) Compared with fluvo-aquic soil, different P-containing materials are more easily fixed in red soil. (3) The difference in potential bioavailability of P from various sources is determined by their distribution to soil labile P fractions.
We attempted to explore promising renewable P-containing materials for achieving a closed cycle of P by understanding the transformation dynamics of different renewable P-containing materials in soil and their P availability. We have supplemented this background in the introduction. To understand the transformation dynamics of different P-containing materials in the soil, we measured the P fractions of the initial soil, four renewable P-containing materials, and two soils with different P-containing materials on days 0,35, and 70 of incubation. The P fractions were not significantly different on day 70 of incubation compared to day 0 of incubation. Therefore, we analyzed the data from day 70 of incubation in the manuscript. However, we did not realize that these data are indispensable to understanding the mechanisms of transformation of different P-containing materials in two soils. The analysis and discussion of these data have been supplemented in the modified manuscript. We believe that this study is helpful and meaningful for understanding the mechanisms of P-containing material transformation in different soils.
And the conclusions were modified as follows: Compared with other renewable P-containing materials, CM is a superior source for improving soil P availability in fluvo-aquic and red soils. Compared to fluvo-aquic soil, phosphorus from SSP, PM, and CM were more strongly immobilized in red soil. Further analysis of the P fraction of two soils with different P-containing materials at days 0,35 and 70 of incubation revealed that the distribution of CM to the soil labile P fraction was significantly increased compared to other renewable P-containing materials. And compared with fluvo-aquic soil, the contribution of different P-containing materials to the labile P fraction of red soil was significantly decreased. Changes in P fractions at different incubation periods in soils with different P-containing materials show that most soil P fractions have no significant difference on day 70 of incubation compared to day 0 of incubation. That suggests, in the short term, the difference of potential bioavailability of P from various sources is determined by the distribution to soil labile P fractions rather than its transformation in the soil. In general, there is promising potential to reduce P limitation by recovering cattle manure as an alternative source of P supply. This study provides a basis for closing the P cycle in agricultural systems and for sustainable on-farm P management strategies.
2. A second point is about the recycled fertilizer/amendment material: why these specific materials were chosen? For example, why include maize straw, which is commonly left in the field and therefore does not constitute an external P input? In addition, these materials are poorly characterized. The total NPK contents are not sufficient to characterize these materials as already pointed out by the first reviewer. Information concerning the repartition between inorganic and organic P as well as the water-soluble or bicarbonate-soluble P forms in the fertilizers should be provided. I wonder why the sequential extraction was not performed on these products. A more detailed characterization of the applied material would help a more mechanistic interpretation of the results. Additional variables, such as dissolved and total organic carbon in these products, would help interpret the results. Dissolved organic compounds, for example, might displace some adsorbed phosphorus, thus increasing its availability. The Discussion Section “Large variability for soil P availability…” would greatly benefit and be less speculative if a more detailed characterization of the organic materials was performed.
Thanks. In this study, we choose poultry manure, cattle manure, maize straw, and bone meal as the renewable P-containing materials to conduct research. Poultry manure and cattle manure is widely used as renewable P-containing materials in current agricultural production. More importantly, the composition of manure P is affected by the digestive system difference between ruminants and non-ruminants, and the role of this difference in the subsequent P transformation process needs further study (Freiberg et al., 2020; Li et al., 2014). Meanwhile, straw turnover is usually applied directly to the soil in agricultural practice, and the P availability in straw requires in-depth analysis. The bone meal which can be recycled and used as a large amount of organic fertilizer in the future remains unclear in terms of P reuse (Ylivainio et al., 2008). We have supplemented the description of the organic materials in the Introduction.
As suggested, we analyzed all P-containing materials including total organic carbon and P fractions and other physicochemical properties before the start of incubation experiments. We have supplemented this detailed information in the modified manuscript. And we supplemented the discussion related to the P forms from raw materials.
3. The third point concerns the data analysis and other soil variables. The Olsen P and labile P fractions from the sequential extraction are correlated in the structural equation model because the P extracted with these two procedures is largely the same (L232-234 and L343-344). For this reason, it is confusing to state that the labile P fractions and the moderately labile P fractions had positive effects on soil Olsen P (L232-233) and other similar expressions. To provide a more mechanistic understanding using the SEM, it would be useful to include independent soil variables, such as clay content, iron oxides content, soluble organic carbon (which is expected to vary with the addition of organic material), which are all known to influence the sorption/desorption reactions of P in soils and therefore its availability.
Thanks for your suggestion. We attempted to better understand the contribution of different P fractions to the variation of soil Olsen-P concentration and the effects of environmental factors on P transformation by structural equation modeling. We have redescribed the SEM results in the modified manuscript.
It is also not clear which data were used to build the SEM, i.e. corresponding to which time points of the incubation.
Thanks. All data for the structural equation modeling were obtained from measurements on day 70 of incubation. We have supplemented this information in the modified manuscript.
Finally, language editing is needed, paying attention also to terminology. For example, the P fractions are most of the time called labile/moderately labile, etc., but sometimes the words “stable” or “active” or “inert” are used. This might create confusion, as these terms are not specifically defined. I suggest adopting consistent terminology throughout the manuscript. Another point: according to their NPK content, some of the organic products, ex maize straw, are technical amendments and not fertilizers.
Good suggestions. During the revision process, we have also done very careful language polishing accordingly. We carefully proofread the whole manuscript and standardized the terminology throughout the manuscript. In addition, we agreed with the reviewers' suggestion to define organic production as fertilizers are not strictly. We have modified the expression throughout the text accordingly.
Minor comments:
Please check throughout the manuscript the numbers after the decimal point in the percentages (sometimes zero, one or two numbers are shown, ex line 181, line 200, line 206) and homogenize to significant precision.
Thank you. We have improved this in the modified manuscript by homogenizing the number of decimal places in percentages to one digit throughout the manuscript.
L45-46: “the attendant environmental…” unclear formulation, please revise.
We have revised the sentence as follows: excessive application of phosphate fertilizer is a common phenomenon, which leads to soil P accumulation, water pollution, and crop quality decline.
L58: “it also affects” not clear what it refers to
Thanks. We have revised the sentence as follows: These renewable P-containing materials can also affect the P kinetics of the soil by changing the adsorption capacity of the soil to P.
L79-80: there are many papers published on the effect of renewable P-containing materials/amendments on soil P fractions (see the non-exhaustive list above). I suggest checking and integrating this literature into the introduction
Thanks for your suggestions. We have supplemented the introduction to the modified manuscript with a description of these research advances. And, the initial sentence has been modified as follows: Quantifying the transformations of different P-containing materials in soils with different soil conditions is necessary to enhance P utilization and reduce P resource limitation.
L109-112: other properties of the two soils such as the mineralogy or at least the texture would be useful, as well as a classification of the soils such as according to the international World Reference Base (WRB)
We agree with these comments. We have supplemented the details of these two soils in the materials and methods, to provide a reference for the wider application of this study. The modified as follows: Soil samples were collected from fluvo-aquic soil (calcareous alluvial soil) in Hebei Province and red soil (ultisol) in Yunnan Province. The soil texture of fluvo-aquic soil is silt loam soil with 7.9% of clay (<2 μm), 55.3% of silt (2–20 μm), and 36.8% of sand (20–2,000 μm). The soil texture of red soil is clay with 47.5% of clay (<2 μm), 25.3% of silt (2–20 μm), and 27.2% of sand (20–2,000 μm).
L117: please, specify whether the P and K concentration in the products are given as P2O5 and K2O or as P and K. It is always preferable to express them as P and K, see:
Thanks. The P, K concentrations of all P-containing materials are indicated by total P and total potassium. We have emphasized this in the Materials Methods section of the modified manuscript.
L127: please, specify to what the percent of soil moisture is referred to, e.g. water holding capacity or soil weight …
We have modified the sentence as follows: During the whole incubation stage, the gravimetric soil water content was kept at about 30% by soil weighing.
L122-123: what is the rationale for this quantity of P added?
The amount of P addition is based on the sufficient soil P amount of most crops to ensure the growth which is derived from the previous study (Kamran et al., 2019; Frazao et al., 2019). We have supplemented the modified manuscript with citations to relevant publications.
L143: “quantitation” is rather “quantification”?
This word has been modified accordingly.
L184: what are these ranges referred to? Are those the time points?
Data refer to the percentage increase in Olsen-P concentration in soils with CM compared to soils with other renewable P-containing materials. The description has been modified in the manuscript.
L190: “soil P fractions” instead of “fractionations”
Thank you. We have modified this in the manuscript.
L191-192 and L214: does the P added was completely recovered in the extracted fractions or not? This information is not easy to infer from table 2 or figure 3 but it would be useful to verify how much of the added P was not accounted for in the sequential extraction end ended up into non-extractable P.
Thank you for your suggestion. Except for the maize straw, all P-containing materials were well recovered during the measurements. We have supplemented the discussion of this result in the manuscript.
L225-226: “and more inositol… both soils” awkward formulation, please re-word
Thank you for pointing this out. We have revised the sentence as follows: Compared with other P-containing materials, the content of inositol hexakisphosphate in the two soils with PM increased significantly " in the modified manuscript.
L226 “supplemented both soils”, please reformulate
Thank you. We have revised the sentence as follows: Although the detected signals were weak, compared with SSP, more signals monoester P and inositol hexakisphosphate were detected in fluvo-aquic soil and red soil with PM and CM.
L269: what does “drab soil” means?
"drab soil" is a soil class according to the Chinese soil genetic classification, which corresponds to the Alfisols of the Soil Taxonomy, and here we follow the author's expression in the cited publication.
L279 “found rapid integration” please, reformulate this sentence
We have modified this in the manuscript.
L307-310: please refer to the supplementary figure showing pH values.
Thank you for your suggestions. We have supplemented the modified manuscript with a description of the changes of pH in soil with different P-containing materials.
L343-344: The P extracted with the Olsen extractant largely overlaps with the labile fractions of the sequential extraction. See also the third main point.
Thank you for your suggestion. We have redescribed the results of structural equation modeling in the modified manuscript.
Table 2: I am surprised by the very good precision of the measurements in some fractions, such as in the NaOH-Po, for which, in my experience, the variability usually is quite large. Are those analytical or real replicates?
We sieved all P-containing materials and soil through a 2 mm sieve before arranging the test and then mixed the soil with the P-containing materials thoroughly. And the samples were well mixed when collecting the samples. This was done to minimize errors caused by the uneven distribution of the samples. And, we strictly managed the environmental temperature and chromogenic time in the operation of the test. All samples were measured under the same conditions to minimize the effects of P transformation on the results during the extraction process. We believe that these results can be reproduced.
Not all the figures in supplementary materials are referenced in the text
Thank you for your suggestion. We have checked the whole manuscript in detail and supplemented the modified manuscript with a description of all the tables and figures in the supplementary materials.
References of response to referee comments
Frazao, J. J., Benites, V. D., Ribeiro, J. V. S., Pierobon, V. M., and Lavres, J.: Agronomic effectiveness of a granular poultry litter-derived organometal phosphate fertilizer in tropical soils: Soil phosphorus fractionation and plant responses, Geoderma, 337, 582-593, https://doi.org/10.1016/j.geoderma.2018.10.003, 2019.
Freiberg, Y., Fine, P., Levkovitch, I., and Baram, S.: Effects of the origins and stabilization of biosolids and biowastes on their phosphorous composition and extractability, Waste Management, 113, 145-153, https://doi.org/10.1016/j.wasman.2020.06.002, 2020.
Kamran, M. A., Xu, R. K., Li, J. Y., Jiang, J., and Shi, R. Y.: Impacts of chicken manure and peat-derived biochars and inorganic P alone or in combination on phosphorus fractionation and maize growth in an acidic ultisol, Biochar, 1, 283-291, https://doi.org/10.1007/s42773-019-00022-5, 2019.
Li, G. H., Li, H. G., Leffelaar, P. A., Shen, J. B., and Zhang, F. S.: Characterization of Phosphorus in Animal Manures Collected from Three (Dairy, Swine, and Broiler) Farms in China, Plos One, 9, https://doi.org/10.1371/journal.pone.0102698, 2014.
Ylivainio, K., Uusitalo, R., and Turtola, E.: Meat bone meal and fox manure as P sources for ryegrass (Lolium multiflorum) grown on a limed soil, Nutrient Cycling in Agroecosystems, 81, 267-278, https://doi.org/10.1007/s10705-007-9162-y, 2008.
Citation: https://doi.org/10.5194/soil-2021-127-AC2
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AC2: 'Reply on RC2', Yuan Wang, 16 Mar 2022
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EC1: 'Comment on soil-2021-127', Luisella Celi, 25 Apr 2022
Dear Authors,
I have completed my evaluation of your manuscript, after your reply to reviewers comments. Your replies have been addressed very carefully, but the criticisms were hard and require a major revision of your paper. As I wrote in the previous evaluation, I invite you to resubmit your manuscript incorporating all revisions you suggested in the replies. Please resubmit your revised manuscript soon.
When revising your manuscript, please consider all issues mentioned in the reviewers' comments carefully. Please note that your revised submission may need to be re-reviewed, due to the strong criticisms arosen by the reviewers.
Kind regards,
Luisella Celi
Topical Editor
Citation: https://doi.org/10.5194/soil-2021-127-EC1
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