This study was conducted in the locality of Guiring, situated in the Diamaré Division (Maroua III Subdivision) in the Far-North Region of Cameroon, located between 10° 32^′21.8^′′ and 10°41^′55.7^′′ North latitude and 14°15^′33.8^′′ and 14°29^′42.0^′′ East longitude (Fig. 1). The area has a Sudano–Sahelian climate (Suchel, 1987), with a short and irregularly distributed rainy season of four months from June to September (Aridity index > 20), followed by a long dry season of eight months lasting from October to May (Aridity index < 20). The average annual rainfall is approximately 792.25 mm, and the average annual temperature reaches 27.7 °C (Table 1). The highest temperatures are recorded in April, while the lowest occur in January. The terrain is mainly characterized by a relatively flat topography, marked by several ecological zones, including the Sahelo–Sudanian domain, the elevated Sudanian domain, and the periodically flooded Sahelian domain. The substratum consists of alluvial deposits of Quaternary age (Tamen et al., 2015; Gountié et al., 2019). The vegetation consists of scattered trees and shrubs associated with grasses. Among the most representative species are Acacia seyal, Balanites aegyptiaca, Faidherbia albida, and Ziziphus mauritiana (Letouzey, 1985).

The experimental design is a completely randomized block design with six (06) treatments (T0, T1, T2, T3, T4, T5) as described in Table 2 and four replicates, resulting in twenty-four plots (6 × 4) (Fig. 2). The choice of a completely randomized block design accounts for environmental heterogeneity and variability in the soil's natural fertility by randomly distributing treatments within each block, thereby minimizing the influence of uncontrolled factors. Each experimental unit received one of the recommended treatments, T0, T1, T2, T3, T4, and T5 (Table 2). Treatment T0 corresponds to the plot that received no input. It serves as the initial reference for evaluating the effects of the various treatments. To enable an objective and effective comparison of the treatments, a standard treatment based on synthetic NPK fertilizer combined with urea (T5) was included, also representing a control, a reference fertilization practice in the region recommended by CIFOR-ICRAF (2024). After the experimental setup was established and the seedlings had emerged, the rock powder was applied locally, directly into each planting hole. It was incorporated to a depth of approximately 5 cm to reduce leaching by water and dispersion by wind. This targeted incorporation enhances the availability of nutrients at the root level while minimizing losses. The maize density was 0.8 m × 0.3 m, with 2 to 3 seeds needed per hole. Two weeks after sowing, thinning was performed to leave one plant per cluster. In each experimental unit, a yield square was demarcated by eliminating plants located at the edges. Parameters were measured on the three central lines, and the four best plants from each line were selected, for a total of 12 plants per plot. A total of 288 plants were retained for all replicates. The plant material used is the CMS-9015 variety of maize, developed by IRAD, which is an open-pollinated variety. This variety is specifically adapted to the Sudanese-Sahelian zone of Cameroon. Under normal conditions, it produces grain yields ranging from 4 to 4.5 tha-1, with a vegetative cycle of 95 d. Manual weeding was carried out throughout the experiment, based on the appearance and development of weeds, to prevent excessive competition with the crops.

Samples of trachyte (Fig. 3a) were collected from the localities of Zamai, at 10°38^′06^′′ north latitude and 13°53^′55^′′ east longitude and that of basalts (Fig. 3b) from the locality of Gawar, at 10°30^′50.7^′′ north latitude and 13°50^′25.68^′′ east longitude. Approximately 500 kg of each type of rock were sampled. These samples were then carefully transported for grinding, thin section preparation, petrographic analyses, and geochemical analyses. In total, 3 samples of trachyte and 3 samples of basalts were subjected to petrographic and geochemical analysis in the laboratory.

The rock sample was fragmented and passed through a ball mill, then sieved using a 2 mm mesh to obtain powder less than 2 mm (Fig. 3c and d). This powder was composed of 49 %, 22 % and 29 % of fractions passing through 0.8, 0.3, and 0.1 mm sieves, respectively. In total, 100 kg of trachyte powder and 100 kg of basalt powder were obtained.

The petrographic analysis was carried out on thin sections prepared at the Tokyo Institute of Technology, Japan. The microscopic description was done in the geology laboratory at the University of Maroua (Cameroon) using an optic microscope to examine the rock samples in detail. This phase allowed for the precise identification of the different minerals present in each sample, based on their optical and textural characteristics. The observations focused on mineralogical assemblages, grain shapes and the relationships between the various minerals.

For the measurements of trace and major elements, all samples were crushed into millimetre-sized fragments using a jaw crusher, and fragments with saw and hammer marks were carefully separated. After each sample, the jaw crusher was systematically cleaned with compressed air and deionized water. The major elements and some trace elements, including scandium (Sc), cobalt (Co), vanadium (V), nickel (Ni), and chromium (Cr), were analysed by X-ray fluorescence (XRF) using a Rigaku RIX2100 (manufactured by Rigaku Corporation, Japan) at Osaka City University, Graduate School of Science in Japan. The trace element concentrations in the samples were determined by ICP-MS (manufactured by Thermo Fisher Scientific, USA) at the Tokyo Institute of Technology, Japan, in accordance with the method described by Yokoyama et al. (1999). Approximately 50 mg of rock powder were digested with nitric acid (HNO3), perchloric acid (HClO4), hydrochloric acid (HCl), and hydrofluoric acid (HF). Before acid digestion, enriched spikes of 113In and 203Tl were added to the sample to serve as internal standards during measurement. The data reported by Makishima and Nakamura (2006) were used to calibrate the trace element concentrations against the basalt and rhyolite standards JB-3 and JR-1, respectively. The typical analytical reproducibility (2σ) was 4 % for niobium (Nb) and lead (Pb), 5 % for yttrium (Y) and tantalum (Ta), and < 3 % for other trace elements.

The fieldwork was carried out in two phases. The first phase consisted of direct observation and a detailed description of the study site and its surroundings. In the second phase, a representative soil profile (10°33^′17^′′ north latitude, 14°22^′16^′′ east longitude, 386 m of altitude) with a thickness of 270 cm was excavated in a flat relief, under highly anthropogenized vegetation, and described in situ following the guidelines for soil profile description according to Baize and Jabiol (2011). The soil description took into account several parameters: colour, porosity, texture, coarse elements, structure, biological activity, thickness, and the boundaries between horizons. The colour was determined in its dry state using the Munsell Soil Colour Charts (2009). A total of six (06) samples, each weighing approximately 0.5 kg, were collected from the different horizons of the profile. The collected samples were placed in polyethylene bags, carefully labelled, and prepared for laboratory analysis.

In the laboratory, the main analyses focused on mineralogical and physicochemical analyses. Particles size distribution was performed using the Robinson pipette method on air-dried, ground, and 2 mm-sieved samples. The pH was measured in a soil-water suspension, then in a normal potassium chloride solution at 1:2.5 ratio using a glass electrode pH meter. Exchangeable bases (calcium: Ca2+, magnesium: Mg2+, potassium: K+, and sodium: Na+) were extracted from the soil using a pH 7 ammonium acetate solution and measured by atomic absorption spectrophotometry. The total exchangeable bases (TEB) was determined by adding the concentrations of Ca2+, Mg2+, K+, and Na+. Cation exchange capacity (CEC) was measured using an ammonium acetate solution at pH 7, following a three-step process: washing the soil with alcohol to remove the ammonium solution saturating the pores, determining NH4+ by Kjeldahl distillation after quantitative desorption with KCl. The CEC of the clay fraction was calculated from the CEC at pH 7, organic carbon content, and clay percentage. Base saturation (BS) was calculated using the formula (TBE/CEC) × 100. Total nitrogen (N) was determined by the Kjeldahl method. Organic carbon (OC) was measured by wet oxidation according to Walkley and Black (1934) using a sodium dichromate and concentrated H2SO4 mixture. Organic matter (OM) content was calculated by multiplying the OC by 1.724, and the C/N ratio was determined. Available phosphorus was measured using the Bray no. 2 method (Bray and Kurtz, 1945). Soil classification was done according to IUSS Working Group WRB (2022).

Mineralogical analysis was carried out using infrared (IR) spectroscopy, a non-destructive analytical method widely used to identify and characterize the functional groups present in samples. This technique provides detailed information about the chemical bonds and molecular structures of minerals. Diffuse reflectance IR spectra were recorded in the range of 4000 to 400 cm-1 using a Perkin Elmer 2000 FTIR spectrometer (Perkin Elmer, Waltham, MA, USA), equipped with a DTGS (deuterated triglycine sulphate) detector, optimized for high sensitivity and precise resolution. To avoid contamination from atmospheric moisture and ensure the reliability of the results, measurements were carried out under strictly controlled environmental conditions. This method not only allows for the identification of minerals present in the soil but also helps describe their local chemical environments, providing a deeper understanding of the composition and properties of soils.

The percentage of nitrogen, potassium and phosphorus in rock powder was calculated using the chemical composition of the rock. To calculate the quantity of each element in the NPK fertilizer, the percentages indicated on the label (14-24-14), the molar masses of these elements and the quantity of fertilizer were used. The percentage of nitrogen in urea was calculated using the amount of nitrogen and the molar mass of urea. The amounts of nitrogen, phosphorus and potassium used are shown in Table 3.

The pedoclimatic assessment aimed to determine the suitability of the study area for maize cultivation based on climatic data (precipitation, temperature, relative humidity, and insolation) collected at the Maroua-Salak station (Cameroon, 10°27^′0^′′ north latitude and 14°15^′0^′′ east longitude) between 1980 and 2020, and the pedological characteristics of soils such as topography, flooding, texture, depth, and cation exchange capacity, base saturation, organic carbon, pH and salinity, in accordance with the climatic conditions and requirements of crops (Sys, 1985; Sys et al., 1993; Issiné et al., 2022). It allows to identify the potential limiting factors for maize cultivation. A climatic index (CI) was calculated using the parametric formula (Sys, 1985): CI=Rmin×A100×B100×…, where Rmin is the smallest value, A,B,… are the other parametric values. Adjustments are made if the CI falls between 25 and 92.5.

The pedological assessment used a table of soil characteristics to determine a land index, based on similar parametric values using the formula (Sys, 1985): LI=Rmin×A100×B100×…,

The calculation of the CI and LI allows for an integrated assessment of agroclimatic and soil quality for agricultural production.

The growth and yield parameters of maize, including germination rate, plant height, number of leaves per plant, stem diameter, ear length, ear diameter, ear weight, 100-grain weight, and grain yield (kgha-1), were measured. To minimize the influence of edge effects on the average value of the response variables of interest, only the plants located at the centre of each experimental plot were considered for measurements. The germination rate was assessed 10 d after sowing by counting the number of germinated seeds in each plot. It was calculated using the following formula (Ellis et al., 1986): Germination Rate(%)=Number of germinated seedsTotal number of seeds sown×100

Plant height was measured using a tape measure, recording the distance from the soil to the top of the stem, with measurements taken every 21 d. These measurements were performed on a representative sample from each plot and an average value was considered (Cox and Andrade, 1988). The number of leaves was counted by tallying the leaves deployed on the main stem, with an average estimation made every 3 weeks (Cox and Andrade, 1988). The stem and ear diameter were measured using a calliper, respectively before and after harvest (Ngoune Tandzi and Mutengwa, 2019). The ear length, measured from base to tip, was recorded with a tape measure when the ears were mature. The weight of the ears was obtained by weighing them with a high-precision electronic scale after harvest (Muthaura et al., 2017). The weight of 100 randomly selected dried maize grains was also measured using a precision electronic scale (Soleymani, 2018). The yield per hectare was estimated by harvesting a representative portion of each plot, weighing the harvest, and then extrapolating the results to the hectare scale using a conversion factor (Soleymani, 2018).

Statistical analyses focused on the physicochemical properties of soils as well as the growth and yield parameters of maize. The physicochemical properties of soils were subjected to standard statistical analyses, including mean, maximum-minimum values, standard deviation, and coefficient of variation. The normality of the distribution was assessed using the Anderson–Darling test. Relationships among the various soil parameters were examined using Spearman's correlation test, with a significance threshold set at p < 0.05. Since the data distribution did not follow a normal law, a logarithmic transformation was applied to measured plant parameter values (Daumas, 1982). Subsequently, the data from plants within the same plot were averaged to produce a single value per replicate, thus representing an independent experimental unit. This approach aimed to avoid pseudo-replication in the statistical analysis. A two-factor analysis of variance (two-way ANOVA) was then performed to assess the existence of statistically significant differences (p< 0.05) between treatments. In case of significant differences, a Tukey's HSD post hoc test was conducted to precisely identify the groups showing differences. All statistical analyses were carried out using the R software (R Core Team, version 4.5.0).

Petrographically, trachyte outcrops in the form of slabs in the Zamai locality and exhibits an aphyric texture, with rare phenocrysts (≤ 5 %). These scarce phenocrysts are mainly composed of amphibole (Fig. 4a), sanidine (Fig. 4b), sometimes associated with clinopyroxene. Sanidine, characterized by elongated euhedral prisms reaching up to 0.6 mm × 1.8 mm, displays simple Carlsbad twins (Fig. 4b). The trachytes are composed of feldspar microliths, accompanied by a low proportion of clinopyroxene and oxides (Fig. 4a andb). Basalts outcrop as lava flows, exhibiting well-defined columnar joints and a porphyritic texture. Plagioclase, olivine, and clinopyroxene constitute the phenocrysts (Fig. 4c andd). Olivine, present in some samples, is often altered to iddingsite. Peridotite xenoliths are also observed in some samples, containing approximately 65 % olivine and 35 % pyroxene. Plagioclase microliths, associated with clinopyroxene, olivine, and oxides, are the main components of the basalt matrix. Microliths and volcanic glass constitute the groundmass of basalts and trachytes.

From a geochemical perspective, the concentration of major and trace elements in the studied rocks are summarized in Table 4. Trachyte exhibit variations in major element contents across samples. The SiO2 content ranges between 65.3 % and 66.5 %, meanwhile the TiO2 content varies from 0.2 % to 0.3 %. The Al2O3 content remains constant at 16.3 %, whereas Fe2O3 concentrations fluctuate between 4.4 % and 5.6 %. The contents of CaO and K2O show variations ranging from 0.6 % to 1.1 % and 4.7 % to 4.8 %, respectively. Regarding basalts, notable variations are also observed in the proportions of major elements. The SiO2 content ranges from 40.9 % to 41.3 %, while TiO2 content is between 4.2 % and 4.3 %. Similarly, the percentage of Al2O3 fluctuates between 13.2 % and 13.4 %. Fe2O3 concentrations vary slightly, ranging from 15.3 % to 15.4 %, while CaO content is between 10.1 % and 10.4 %, and K2O ranges from 1.4 % to 1.7 %. These subtle yet significant differences highlight the important geochemical variations between trachyte and basalt samples, underscoring the diversity of their mineralogical composition.

Trace element concentrations in the trachyte show significant fluctuation. The chromium (Cr) content remains relatively constant at 2 ppm, while other elements such as nickel (Ni), strontium (Sr), rubidium (Rb), yttrium (Y), barium (Ba), and niobium (Nb) exhibit more pronounced variations, ranging from 7.2 to 9.1 ppm, 7.3 to 20.9 ppm, 136.2 to 148.8 ppm, 60.4 to 97.1 ppm, 16.2 to 48.9 ppm, and 194.2 to 197.3 ppm, respectively. In contrast, basalts show much higher concentrations of Cr (176.1 to 183 ppm), Ni (269.6 to 277.7 ppm), Sr (1648.5 to 1685.5 ppm), and Ba (561.1 to 572.7 ppm). However, the basalts have relatively low levels of Rb (18.9 to 23.5 ppm) and Y (22.9 to 23.2 ppm) compared to the trachyte (Table 4). These variations indicate substantial differences in trace elements between trachytes and basalts, reflecting distinct geochemical signatures.

The studied soil profile consists of six horizons (Fig. 5) divided into four distinct textural groups: sandy loam, loamy sand, loamy clayey sand, clayey sand and sandy. The colours range from light yellow-brown (10YR 5/4) to dark brown (7.5YR 3/2), passing through light yellow (10YR 5/4) and up to pale yellow (2.5Y 7/4). Each horizon has a fine, granular structure with significant biological and matrix porosity, promoting good permeability and optimal friability. The transitions between horizons are gradual and regular (Table 5).

Mineralogically, the infrared spectra of the soil, illustrated in Fig. 6, revealed the presence of kaolinite, smectites, sepiolite, and quartz. In the high-frequency region, the hydroxyl groups display two bands at 3774–3622 cm-1, corresponding to the stretching vibrations of the OH- groups characteristic of kaolinite according to Farmer and Russell (1964) and Frost and Johanson (1998). The low intensity absorption band located at 1621 cm-1 is attributed to water molecules, possibly associated with smectites. Sepiolite is primarily distinguished by the band at 531 cm-1. The presence of quartz is manifested by the peaks at 1003, 774, 693, 531, and 459 cm-1, which correspond to Si-O vibrations.

The particle size distribution is dominated by sand fraction with proportions varying from 62 % to 82 %, corresponding to a mean value of 76.2 ± 9.2 % (Table 6). Clay constitutes the second important particle size fraction, with proportions ranging from 13 % to 23 %, with a mean value of 16.3 ± 5.2 %. Silt fraction appears to be the least abundant, with proportions varying from 5 % to 15 %, with an average of 9.2 ± 4.9 %.

The analysed soils exhibit a pH ranging from acidic to slightly basic (6.8 to 7.2), with an average of 7.0 ± 0.2. Except for clay, which was strongly positively correlated with pH (r = 0.9, p< 0.05), no significant correlations were observed between pH and other soil parameters. The organic matter (OM) and total nitrogen (N) contents are relatively low, with values ranging from 1.3 % to 3.2 %, and 0.1 %, with averages of 2.6 ± 0.7 %, and 1.1 ± 0.0 % (Table 6). The C/N ratio, relatively low, varies from 6 to 16, with an average of 12.3 ± 3.6. Base saturation (BS) varies between 23.6 % and 42.4 %, with an average value of 31.1 ± 7.4 % (Table 6).

The total exchangeable bases (Ca2+, Mg2+, K+, and Na+) exhibit notable variation across the soil profile. Calcium (Ca2+) and magnesium (Mg2+) concentrations are low to moderate, with values ranging from 2.6 to 6.0 cmolckg-1 in the case of Ca2+ and 0.7 to 5.4 cmolckg-1 for Mg2+, with respective averages of 3.9 ± 1.5 and 2.5 ± 1.6 cmolckg-1 (Table 6). Regarding potassium (K+) and sodium (Na+), their contents are very low to low, oscillating between 0.1 and 0.4 cmolckg-1 for K+ and between 0.1 and 0.6 cmolckg-1 for Na+, with respective averages of 0.2 ± 0.1 and 0.3 ± 0.2 cmolckg-1 (Table 6). Mg2+ shows a positive correlation with clay (r = 0.6, p< 0.05) and pH H2O (r = 0.7, p< 0.05). K+ is strongly correlated with clay (r = 0.8, p< 0.05) and moderately with pH H2O (r = 0.7, p< 0.05). The total of exchangeable bases (TEB) ranges from 5.1 to 8.9 cmolkg-1, with an average value of 6.9 ± 1.7 cmolckg-1 (Table 6). This TEB shows a moderately positive correlation with clay content (r = 0.8, p< 0.05). The cation exchange capacity (CEC) displays relatively high values, ranging from 18.7 to 25.0 cmolckg-1, with an average of 22.1 ± 2.5 cmolckg-1 (Table 6). It shows a strong correlation with the clay fraction (r = 0.8, p< 0.05), as well as with pH H2O (r = 0.8, p< 0.05). It is also moderately correlated with potassium (K+) (r = 0.8, p< 0.05) (Table 7). Phosphorus (P) shows concentrations ranging from low to medium, with values between 12.6 and 30.3 mgkg-1, and an average of 19.0 ± 7.0 mgkg-1 (Table 6). Phosphorus shows a strong correlation with clay content (r = 0.9, p< 0.05) and with CEC (r = 0.8, p< 0.05) (Table 7). Base saturation (BS) presents values ranging from 23.6 % to 42.4 %, with an average of 31.1 ± 7.4 %. Electrical conductivity varies from 0.0 to 1.2 dSm-1, with an average of 0.3 ± 0.5 dSm-1 (Table 6). The latter is strongly correlated with Na, with a coefficient of r = 0.9 (p< 0.05).

Morphologically, the study soil profile is characterized by an alternation of different soil textures which are sandy loam, loamy sand, loamy clayey sand, clayey sand and sandy, in line with the alluvial nature of the parent material. This alternation of soil textures is confirmed by the zigzag evolution of the percentage of different particle size distribution fraction noted in Table 5. These characteristics correspond to those of Fluvisols. Base saturation ratio in all soil horizons is below 50 %, leading to the choice of Dystric as principal qualifier. The light colour of soils and the organic matter content (< 3 %) lead to classify the studied soils as Ochric Dystric Fluvisols according to the IUSS Working Group WRB (2022).

The study area presents very favourable climatic conditions for the growth and yield of maize. The average temperature of 26.6 °C during the growing cycle presents a slight limitation for the production of maize (S1-1) (Table 8). The precipitation during the growing cycle, approximately 649 mm, has no limitation for the cultivation of maize. The climatic index of 91.4 (S1-0) indicates that there are no major limitations for maize cultivation in this area. This means that climatic conditions are favourable, suggesting the possibility of achieving optimal yields.

The low slope (1 %), presents a slight limitation (S1-1). The risk of flooding is non-existent (FO), and drainage is of good quality, indicating that there are no constraints related to soil moisture (S1-0) (Table 9). The soil texture, of the sandy-loamy type (SL), classified as S2, has proven to be a moderate limitation with a parametric value of 67.4. The soil depth, greater than 100 cm, is very suitable (S1-0), which is optimal for root development. Presence of coarse fragments displays a slight limitation (S1.1), with a parametric value of 96.3 for maize production (Table 9). The apparent cation exchange capacity (CEC) of the soil, classified as S1-1, indicates a slight limitation, with a parametric value of 90. Base saturation and organic carbon content, both classified as S2, reveal moderate limitations, with respective parametric values of 75.2 and 72.8. The soil pH (S1-1) and the electrical conductivity is suitable (S1-0) for the production of maize although there is a slight limitation related to pH (Table 9). The overall land suitability index is 62.4, which classifies it as S2sf, indicating moderate suitability for cultivation, primarily due to constraints related to the soil's physical properties and fertility.

Particle size analyses revealed that the upper part of the soil profile primarily consists of a sandy-loam horizon, characterized by a high sand content ranging from 67 % to 82 %. The underlying horizons exhibit a succession of sandy and sandy-clay textures, with similar sand proportions. These observations are consistent with those observed in Fluvisols from various arid regions around the world (Romanens et al., 2019). The predominance of sand fractions can negatively affect water and nutrient retention capacities while directly impacting plant root development (Basga et al., 2018; Tsozué et al., 2020a). The limited presence of silt particles may help mitigate these effects by enhancing infiltration and slightly increasing the soil's water and nutrient retention capacity (Lu et al., 2020; Tsozué et al., 2021). The clay fraction, ranging from 13 % to 18 %, plays a significant role in the soil's structural stability and fertility, and can enhance both nutrient availability and water retention in the soil (Kome et al., 2019; Gautam et al., 2022).

From a mineralogical perspective, the studied soils are predominantly composed of quartz, along with clay minerals such as kaolinite, smectites, and sepiolite. Kaolinite, an indicator of advanced weathering processes in tropical environments, results from climatic conditions that promote the leaching of basic cations and the neoformation of secondary minerals (Tsozué et al., 2020b; Lyu and Lu, 2024). In contrast, the presence of smectite suggests moderate pedoclimatic conditions with variable humidity, which enhance cation exchange capacity and water retention. However, due to its swelling and shrinking behaviour, smectite could cause drainage problems and surface water stagnation, limiting agricultural use for certain sensitive crops (Hopmans et al., 2021). Sepiolite, on the other hand, is characteristic of semi-arid environments with low leaching rates (Bannari and Abuelgasim, 2021). According to Easwaran et al. (2024), this mineral is notable for its remarkable ability to retain water and nutrients, making it particularly beneficial for soils in arid areas or regions prone to drought.

From a physicochemical perspective, the pH reveals low acidity, typical of soils under a Sudano–Sahelian climate, consistent with the chemical conditions observed in this region (Tsozué et al., 2020a; Tamto Mamdem et al., 2024). The slight acidification, particularly in the surface layer, can be attributed to the leaching of bases and the use of synthetic fertilizers and pesticides (Pahalvi et al., 2021; Sarkar et al., 2024). The strong correlation between pH and cation exchange capacity highlights the importance of regulating pH to optimize CEC and, consequently, improve the availability of essential nutrients for crops (Tsozué et al., 2021; Poggi et al. 2023; Santos et al., 2023; Thiaw et al., 2024). Organic matter plays a key role in soil fertility; its low proportion could be explained by several factors, including overexploitation of agricultural lands and intensive grazing after harvest, the semi-arid climate characteristic of the study area and the sandy texture of the soils (Abdelhak, 2022; Plaza et al., 2018; de Alencar et al., 2024). Improved management practices, such as adding organic matter, crop rotation, or using cover crops to improve soil fertility and overall health, could be corrective measures (Arif et al., 2021; Choudhury et al., 2024; Yang et al., 2024). The very low C/N ratio indicates rapid mineralization, likely related to high temperatures and the sandy texture of the soils (Chen et al., 2024). The low content of available phosphorus in the soil, although essential for crop growth and yield, could be attributed to its fixation on the clay-humic complex, a phenomenon strongly influenced by the clay content, pH, and calcium levels (Joshi et al., 2021; Lotse Tedontsah et al., 2022). The relatively high CEC is a crucial indicator of soil fertility, illustrating its ability to retain and exchange nutrients, essential for plant growth. According to Obi et al. (2020), this suggests that the soil can sustainably provide nutrients. High concentrations of Ca2+ and Mg2+, especially at depth, indicate a good reserve of nutrients for plants (Hechmi et al., 2023). In contrast, the relatively low K+ content could limit plant growth, as potassium is important for photosynthesis and water regulation (Johnson et al., 2022). The moderate Na+ concentration would be beneficial in preventing salinity issues (Hussain et al., 2021). These exchangeable bases play a vital role in plant health and improving agricultural yields (Verma et al., 2024). Electrical conductivity is a key indicator of soil salinity. Since the measured values are low, this would not favour optimal absorption of water and nutrients by plant roots (Golia, 2023).

The release of nutrients from trachyte and basalt powders is a key topic in pedology and geochemistry, particularly in bioweathering (Podia et al., 2023). These processes enhance the bioavailability of essential plant nutrients (Medeiros et al., 2023). Mineral hydration from water input causes swelling and disintegration, releasing cations like K, Ca, and Mg (Ramos et al., 2022; Wakeel, 2013). The release of nutrients from trachyte and basalt powders is governed by interdependent physical, chemical, and biological processes (Swoboda et al., 2022). Basalt, rich in plagioclase feldspars, pyroxenes, and olivine, provides Ca, Mg, Fe, and trace elements. Its high reactivity stems from mafic minerals, which are more easily altered (Ghasera and Rashid, 2024). In contrast, trachyte, mainly composed of alkali feldspars, is a major K source but has lower reactivity due to its felsic nature (Meena and Biswas, 2014; Mbissik et al., 2021). Particle size significantly influences mineral dissolution and nutrient release (Duarte et al., 2013; Burbano et al., 2022; Rodrigues et al., 2024). Acidic pH favours silicate dissolution and K, Mg, and Fe release, while reducing conditions increase Fe and Mn mobility (Wakeel, 2013; Vondráčková et al., 2017). Organic matter and microbial activity play key roles in mineral weathering (Yang et al., 2016; Rout et al., 2024). This microbial activity, coupled with mycorrhizal interactions, enhances mineral breakdown and nutrient uptake (Ma and Yamaji, 2006; Meena and Biswas, 2014). These symbioses boost root access to nutrients and activate biological processes that promote silicate dissolution (Yadegari and Etesami, 2024). These combined mechanisms make trachyte and basalt powders particularly effective in nutrient-deficient soils, facilitating the release of K, Ca, and Mg. High humidity promotes mineral alteration and microbial activity, while excessive rainfall can cause nutrient leaching (Basak and Biswas, 2009; Lima et al., 2010; Duarte et al., 2013).

The climate of the study area offers favourable conditions for maize growth and yield, as evidenced by annual rainfall and the climatic index. Conversely, some edaphic parameters pose moderate limitations, including the sandy-loam texture and low base saturation, which affect water retention and nutrient availability (Verdoodt et al., 2003; Tsozué et al., 2015; Issiné et al., 2022; Scanlan et al., 2022). To address these limitations, adapted management practices are essential. Adding organic matter, such as compost or crop residues, and using cover crops like legumes can improve soil structure and water retention capacity (Obi et al., 2020). Additionally, the application of lime or dolomite could increase calcium and magnesium saturation, while potassium fertilizers can correct low potassium availability (Hechmi et al., 2023). Adding biochar with and without additional compost and manure, identified by Hussain et al. (2021) and Seyedsadr et al. (2022) as an effective solution, enhances water retention and cation exchange capacity, both of which are fundamental properties for the fertility of sandy soils. The use of organic fertilizers is similarly effective in overcoming fertility limitations while promoting sustainable soil management (Van Leeuwen et al., 2015; Das et al., 2024; Robinson, 2024). Trachyte and basalt powders, used as natural amendments, represent a promising alternative for improving soil fertility, especially in semi-arid regions where soils are often degraded by nutrient depletion and poor structure. These powders gradually release essential mineral elements such as calcium, magnesium, and potassium, thereby increasing exchangeable bases and cation saturation (Swoboda et al., 2022; Basak et al., 2023). They enhance nutrient retention, improve soil mineral composition, increase cation exchange capacity, and contribute to sustainable agricultural fertility management (Manning and Theodoro, 2020; Ramos et al., 2022). As slow-release mineral sources, these powders also help restore nutrient balances, improve water retention, and revitalize soil microbial activity (Anda et al., 2015; Ramos et al., 2022; Guo et al., 2023). This is particularly relevant in semi-arid zones, where conventional fertilizers are often ineffective due to rapid nutrient leaching and unfavourable climatic conditions (Ramos et al., 2022; Cardozo et al., 2024).

Trachyte powder, with relatively high concentrations of K2O and Na2O, promotes plant growth, particularly potassium, which is essential for photosynthesis and water regulation. Its low level of Fe and Mg limits its direct nutrient contribution for maize, which primarily requires nitrogen, phosphorus, and potassium for its growth (Reimann et al., 2018; Linhares et al., 2021). In contrast, basalts, characterized by high concentrations of Fe2O3, CaO, TiO2, and P2O5, while exhibiting reduced levels of SiO2 and Al2O3, can serve as a natural nutrient source (Oppon et al., 2023). They are particularly suited to enriching soils' deficient in these elements, thereby improving soil fertility and productivity (Kagou Dongmo et al., 2018; Luchese et al., 2021; Conceição et al., 2022).

The application of rock powders and conventional fertilizers known as reference fertilization practice in the region (T5) led to an increase in essential parameters related to maize growth and yield, compared to the control (T0). Plots treated solely with trachyte and basalt powders exhibited significantly higher growth compared to control plots, confirming their potential as effective amendments for improving maize growth (Ramos et al., 2015, 2017, 2021, 2022; Oliveira et al., 2020; Mein'da et al., 2022; Luchese et al., 2023; Reis et al., 2024). This improvement could influence photosynthesis, biomass production, and even seed quality, contributing to increased productivity and yield (Oliveira et al., 2020; Marinho Viana et al., 2024; Swoboda et al., 2022; Luchese et al., 2023).

There is an overall significant improvement of maize yield, increasing from 646 kgha-1 in the control to 2764 kgha-1 in the plot treated with trachyte powder and 2931 kgha-1 in the plot amended with basalt powder. For NPK + urea as 100 % relative yield, basalt + urea reached 92.6 % and trachyte + urea reached 87.3 % of the maximum yield, whereas the remineralizers alone resulted in relative yields of 80.8 % and 74.7 % for basalt and trachyte, respectively. These results are consistent with the findings of Sánchez-Marañón et al. (2002), who emphasized the need to strengthen fertilization in tropical soils that are inherently poor in nutrients. Although the highest yield was obtained with the application of conventional fertilizers known as reference fertilization practice in the region recommended by CIFOR-ICRAF (2024) (3165 kgha-1), trachyte and basalt powders could be more advantageous due to their local availability, lower cost, and positive effects on the soil (Tamfuh et al., 2020; Ramos et al., 2021; Mbissik et al., 2021). They release nutrients slowly and sustainably over multiple seasons, unlike conventional fertilizers, which provide nutrients rapidly but for a short duration. They help improve soil fertility without causing pollution or harming biodiversity (Nkouathio et al., 2008; Lopes et al., 2014; Oliveira et al., 2020; Luchese et al., 2023).

Although no comparison was made between NPK fertilizers and rock powder, rock powder naturally contains a variety of micronutrients essential for plant health, which are often absent in NPK fertilizers. Deficiencies of micronutrients are major causes of low maize yields in poorly responsive soils (Njoroge et al., 2018). This phenomenon minimizes the agronomic efficiency of N, P and K fertilizers and consequently results in a dwindling economic benefit associated with their use (Njoroge et al., 2018). It is recognised that basalt powder, for example, improves soil fertility and maize nutrition and can help combat plant diseases by strengthening their natural resistance (Conceição et al., 2022). Rock powder can be used in biological agriculture unlike synthetic NPK fertilizers. Rock powder therefore offers a more sustainable and environmentally friendly approach to soil fertilization, improving long-term fertility and reducing the risk of pollution (Nkouathio et al., 2008). It represents an attractive alternative to NPK fertilizers for those seeking to adopt more environmentally friendly and sustainable agricultural practices.