We thank the anonymous reviewer for reviewing this manuscript and their support of this work.

We thank the anonymous reviewer for their succinct summary of our manuscript and for highlighting the positive contribution that they believe this research can bring to soil science and agricultural research communities.  

We thank the review for their advice and will add the following text (underlined) to the Abstract and Introduction:

Abstract: We believe this is the first report of two-dimensional spatially resolved mapping of P bioavailability obtained in situ (field) at the fertiliser band scale in a dryland cropping system.

Introduction, Page 3:  To the best of our knowledge, such an approach has not been used to investigate the availability of P from fertilisers in field trials of major crops, excluding rice, and specifically not in any dryland cropping systems.

Introduction, Page 3: Here, we report the design of a novel field DGT (fDGT) device and its evaluation for visualising and assessing the spatial availability of P from different fertiliser sources in a barley field trial for the first time.

Thank you for the suggestions regarding the Discussion. We will add the following text to the manuscript:

Discussion, Page 9: 

This mechanistic knowledge of how fertilisers behave in the field can be used to drive improvements in management practices and fertiliser formulations, ultimately increasing fertiliser nutrient use efficiency (Lombi et al., 2025). In contrast to the bulk soil, the fertosphere is likely to also have steep gradients for soil pH and EC which can influence nutrient availability. Therefore, by better understanding these spatial differences, agronomic practices could be improved by developing fertiliser formulations with a more sustained nutrient supply, in turn reducing precipitation and fixation reactions, and by optimising the placement of fertilisers (Lombi et al., 2025). For example, for this fertiliser-soil combination (i.e. DAP granules in a calcareous soil), if seeds are placed ≤ 5 mm from the fertiliser, primary roots would be exposed to the highest concentration of available P, but increasing the application rate of P may not be beneficial as the P availability plateau has been reached. In addition, although sorption reactions dominate further away from the granule, vertical spacing between fertiliser and seed bands should not exceed 20 mm due to the limited vertical diffusion of P.

We agree with the reviewer regarding the comment on reduced plant biomass at high DAP rates, and agree that this is an important point. However, we contend that this has already been addressed in the Discussion at Line 188-192:

Line 188-192: The lower biomass at the higher DAP rate, is possibly due to ammonia/ammonium (NH₃/NH₄⁺) toxicity; a known issue when ammoniacal fertilisers are banded in the vicinity of seeds (Pan et al., 2016). A review of the literature in relation to ammonia/ammonium-induced plant toxicity, caused by fertilisers with a high N:P ratio, shows that nutrient uptake, root proliferation and plant biomass can be reduced when NH₃/NH₄⁺ accumulate (Sica et al., 2025).

For Table 2, we appreciate this comment and agree that the pH and EC data were minimally impacted by fertiliser application due to potential masking by the bulk sampling protocol (0-4 cm and 4-6 cm). However, we feel there is still value in presenting these data as there were significant differences in pH (albeit minimal) between the two depths. We feel this information is also important for highlighting the importance of shifting from focussing on bulk chemistry to spatially resolved approaches.

For Figure 2, we will define all abbreviations in the legend and update the figure. The original colour scheme was ‘colourblind safe’, but we will insert a new figure (still colourblind safe) where the treatments are paired together as suggested and the colours better show the grouping i.e. light blue and dark blue for shallow and deep sampling depths. For some treatments due to the colourblind safe scheme a light and dark option is not always available but we will reorder the grouping of treatments to make this image clearer.

For Figure 3, thank you for picking this up. We will amend the figure caption as suggested to more clearly explain the colour scale and how we averaged the XFM data for each horizontal transect to produce 1 point per depth.

Proposed revised Figure 3 legend: Two dimensional phosphorus diffusion images measured using field-deployed DGT in combination with XFM, where (a) are phosphorus XFM images of the DGT binding layers collected from; the diammonium phosphate treatment (DAP) where P was applied at 10 kg ha^-1, the DAP treatment (DAP², 20 kg ha^-1) and Biochar + DAP treatment (20 kg P ha^-1), and (b) labile P concentrations (Cp, μg P L⁻¹) calculated as a function of depth for the three fertiliser regimes tested – obtained by averaging the 2D XFM maps across the horizontal axis i.e. each coloured point in (b) is the average of the Cp values in a horizontal transect across the gel and each transect is 100 um apart. ‘Depth’ is the distance from the soil surface.

We thank the reviewer for their time taken in reviewing this manuscript and their suggestions to improve its quality.