Improving Nitrogen Availability and Crop Productivity Using Bioameliorants in Maize–Soybean Intercropping on Suboptimal Land

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article describes different treatment on maize-soybean systems to improve plant nutrition and yield, the paper is well presented. However, the reviewer has a few comments that hope the authors can help address, please see below:

Figure 3: the error bar and the figure is misaligned. Are set a and b actually statistically different when it comes to concentration of organics?
Figure 5: the error bar and the figure is misaligned. The data is barely showing significant statistical difference.
Section 4.3: please utilize more data in the discussion session.
Section 4.4: when mention high yield, please present numerical measurement of said matrix.

Author Response

Response to Reviewer Comments

Dear Editor and Reviewers,

We would like to sincerely thank you for the valuable comments and constructive suggestions that have greatly improved the quality of our manuscript. We have carefully revised the manuscript according to all the recommendations from both Reviewer 1 and Reviewer 2. All corrections and revisions have been highlighted in blue text in the revised version of the manuscript. In addition, references that were not directly relevant to the content of the paper have been removed to improve focus and clarity.

Response to Reviewer 1

1. Figure 3: The error bars have been removed and replaced with letter notations to indicate statistically significant differences among treatments in the bar charts. This adjustment makes the figure clearer and easier to interpret. The alignment and formatting of the figure have also been corrected to ensure accurate layout and uniform sizing. We further verified the statistical differences, particularly in relation to organic concentration, to ensure accurate interpretation.
2. Figure 5: Similar to Figure 3, the error bars have been replaced with letter notations to more clearly display statistically significant differences. The figure has also been reformatted to improve clarity, with alignment and sizing corrected to achieve consistency across all figures.
3. Section 4.3: The discussion has been expanded with additional supporting data to strengthen the analysis and interpretation.
4. Section 4.4: Numerical measurements have been added to support the statement regarding high yield, providing clear quantitative evidence.

Reviewer 2 Report

Comments and Suggestions for Authors

This study aims to evaluate the effects of different bioameliorant compositions on nitrogen availability, plant growth, and yield in maize–soybean intercropping on suboptimal land.

The experimental measurements seem well done. However, the sampling of soil and plants needs more detail. I think to be worthy of the journal Nitrogen  that there needs to be some analysis and discussion of nitrogen balance. The discussion on bioameliorants is comprehensive. The results need converting to a standard area measure.

Detailed comments:

Section 2.4. Was the AMF inoculum applied to the F0 treatment – this needs specifying? The nitrogen and phosphorus position needs further detailing. The total major nutrients applied, including those in the bioameliorant (maybe include Table 2 here), need converting, as elements, to a standard area format format. As an aside, the application of urea to soybean may well reduce its nitrogen fixation capacity.

Section 2.5. How were the soil samples taken, how many and when (before or after cultivation)? The harvest sampling details are incomplete. Were individual plants harvested, the whole of each plot of maize and soybean, or was only the central row of each crop harvested (best to avoid edge effects)? What was used for the nutrient analysis for nutrient uptake - the whole plant, the cob or just the kernels? How were the samples dried?

There is no Section 2.6.

Figure 3. This is an unusual result for N and P because usually after a crop has grown it greatly reduces the concentration of available nutrients. There should be some discussion of how this occurs made in the Discussion.

Figure 4. Was this for the whole plant or just the cobs and pods? Can you estimate how much of these nutrients was taken up by the plants on a standard area basis?

Figure 6. Please revise the descriptions of the measures to be consistent with the text. It is also desirable if they could be converted to a standard area measure (was there twice the area of corn as soybean harvested?). The grain (kernel) yields are very low at 9-12% of maize cobs and 3-6% of soybean pods, indicating fertility problems possibly resulting from drought stress or overcrowding of the soybeans. An explanation please?

L399. Although the hyphae allow access by plant roots to extra N, the Kjeldahl analysis should have shown this in the soil.

L415 How was NUE estimated?

Author Response

Response to Reviewer Comments

Dear Editor and Reviewers,

We would like to sincerely thank you for the valuable comments and constructive suggestions that have greatly improved the quality of our manuscript. We have carefully revised the manuscript according to all the recommendations from both Reviewer 1 and Reviewer 2. All corrections and revisions have been highlighted in blue text in the revised version of the manuscript. In addition, references that were not directly relevant to the content of the paper have been removed to improve focus and clarity.

Response to Reviewer 2

1. Experimental measurements: More detail has been added regarding soil and plant sampling, including the timing, number of samples, and sampling procedures.
2. Nitrogen balance: A discussion on nitrogen balance has been incorporated to strengthen the ecological interpretation of the findings.
3. Nutrient application: The total amounts of nutrients applied, including those supplied through bioameliorants, have been converted to elemental units on a standard area basis (Table 2 has been revised accordingly). Clarification has also been added regarding the AMF inoculum in the F0 treatment.
4. Soil sampling: Additional details are now provided on how, when, and how many soil samples were collected, as well as the procedures for harvest sampling (whole plots vs. central rows) to avoid edge effects.
5. Plant nutrient analysis: Clarification has been made regarding the plant parts analyzed for nutrient uptake (whole plant, cobs, kernels, etc.) and the drying methods applied.
6. Section 2.6: This section has been corrected and added to provide completeness and consistency.
7. Figures 3, 4, and 6: These figures and their descriptions have been revised for clarity. The results are now presented in a standard area measure to allow proper comparison. The unusual trend of nutrient availability after crop growth has been explained in the Discussion, attributing it to continuous nutrient release and microbial mobilization.
• For Figure 4, clarification is given regarding which plant parts were analyzed, and nutrient uptake is estimated on a standard area basis.
• For Figure 6, the yield data have been revised and described consistently with the text, with conversions to a standard area basis. The low grain-to-pod/cob ratios are explained as likely due to drought stress and interspecific competition in dense soybean planting.
8. Soil nitrogen analysis (L399): Clarification has been added to explain the relationship between hyphal access to nitrogen and the Kjeldahl soil analysis.
9. NUE estimation (L415): The method for estimating Nitrogen Use Efficiency (NUE) has been clearly described to ensure transparency.

We are confident that these revisions address all reviewer concerns and have substantially improved the manuscript.

Thank you again for your thorough review and guidance.

Sincerely,
Wahyu Astiko (on behalf of all authors)

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have improved the manuscript considerably. Thank you for the extra detail.

L339. My first calculation was incorrect. I now believe that the kernel to cob weight in maize was 64.8 to 60.5% and the kernel to pod weight in soybean to be 20.5 to 32.5%, which is still low. Moreover, the highest combined kernel yield of 11.1 kg/plot (25 m²) comes to about 4.4 t/ha, which is on the low side.