Review Reports - Subsoiling Operations Concurrent to the Distribution of Acidity Amendments in the Soil Profile: The Response from Soybeans

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper focused on the evaluation of the effects of the subsoiling operation concomitantly with the application of soil acidity corrector on the nutrition and productivity of soybean crops.Six treatments and four replication were used, compared and analyzed. However, the overall writing of the paper is relatively rough, with unclear logic and structure, less workload, and insufficient in-depth analysis and summary of the results. The overall significance of the paper is also not clearly explained.In my opinion, it is not ready for publication in current form. Here are my specific comments.

1. The abstract is incomplete, lacks research objectives with unclear significance.

2. What is ‘S’ in the abstract?

3. What is the basis for selecting the dosage of improvers in different treatments?

4. Introduction part, the explanation of the impact of cultivation methods and the summary of the use of soybean amendments are not sufficient, the research significance is not explained enough, the purpose is not clear enough, and the hypothesis is not well presented.

5. There is no distribution image of the research area, and the local climate conditions and soil characteristics should be given more accurately.

6. Why is Figure 2 only applicable to the treatment of T4 and T3, and why are other treatments not provided, and the characterization effect of this figure is not significant.

7. The expression of the unit is incorrect, for example, line 135, line 186, ha-1

8. Line 111, missing unit, layer of 0-20,20-40, what units, cm?

9. The meaning of ‘-m’ in Figure 5c?

10. What’s ‘a’ and ‘b’ in Table 2, Table 3?

11. The discussion part is not deep enough.

12. The citation is not correct in the manuscript, especially for the discussion part.

13. Conclusion is hasty and insufficient, besides, only one paragraph is recommended.

Comments on the Quality of English Language

There are issues with the citation of literature, formatting issues in the paper, and difficulty in understanding English expressions. It is recommended to further have native English speakers check and verify your manuscript.

Author Response

Dear editor, below is the file with the corrections/suggestions proposed by the reviewers, referring to the article entitled: Subsoiling operation concurrent to the distribution of acidity amendment in the soil profile: Response from Soybeans.

We emphasize that all corrections/suggestions were taken into account and greatly contributed to improving the quality of the article. We greatly appreciate the opportunity to publish in this renowned journal. FOLLOW THE RESPONSES IN ACCORDANCE WITH THE CORRECTIONS/SUGGESTIONS HIGHLIGHTED BY THE REVIEWERS:REVIEWER 1: 1. The abstract is incomplete, lacks research objectives with unclear significance.Answer: suggestion accepted- The soils of the Brazilian Cerrado region have great agricultural potential, however, they are naturally acidic soils due to the constitution of the source material and the high weathering process. Liming has been the main tool for correcting acidity and supplying Ca²⁺ and Mg²⁺to the soil, however, the effect of the corrector is limited to the soil surface. Therefore, the benefits of liming are restricted to the surface layer of the soil, and consequently, do not solve subsurface acidity problems.2. What is ‘S’ in the abstract?Answer: suggestion accepted- súlfur3. What is the basis for selecting the dosage of improvers in different treatments?Answer: suggestion accepted-

The calculations to determine the dosages of lime used in each treatment were carried out based on the equation proposed by [33], which establishes that the need for lime, in Mg ha^-1, to be applied to the soil, every 20 cm deep, can be obtained by the equation: NL (0-20 cm) = Tx(V2-V1)/PRNT. Where NL represents the need for liming in Mg ha^-1; T refers to the cation exchange capacity at pH = 7.0; V2 represents the base saturation you want to achieve; V1 is the current base saturation and PRNT is the actual total neutralization capacity of the limestone used.

In this way, there are the following quantities of limestone to be applied to the soil, for each treatment, according to the information obtained in the analysis present in the table 1:

T2- Superficial application of limestone: NL (0-20 cm) = 7.60x(60-36.8)/175= 1.00 Mg ha^-1.

T3- Application of limestone using the subsoiler, with a spacing between rods of 0.37 m: NL (0-20 cm) = 7.60x(60-36.8)/175= 1.00 Mg ha^-1, added to the recommendation for a layer of 20-40 cm, NL (20-40 cm) = 5.60x(60-27.5)/175= 1.04 Mg ha^-1; added to the recommendation for a layer of 40-60 cm, NL (40-60 cm) = 4.20x(60-27.1)/175= 0.789 Mg ha^-1, totaling 2.82 Mg ha^-1 of limestone.

T4- Application of limestone using the subsoiler, with a spacing between rods of 0.75 m: NL (0-20 cm) = 7.60x(60-36.8)/175= 1.00 Mg ha^-1, added to the recommendation for a layer of 20-40 cm, NL (20-40 cm) = 5.60x(60-27.5)/175= 1.04 Mg ha^-1; added to the recommendation for a layer of 40-60 cm, NL (40-60 cm) = 4.20x(60-27.1)/175= 0.789 Mg ha^-1, totaling 2.82 Mg ha^-1 of limestone.

T6- Subsoiling, followed by surface liming: NL (0-20 cm) = 7.60x(60-36.8)/175= 1.00 Mg ha^-1.

Introduction part, the explanation of the impact of cultivation methods and the summary of the use of soybean amendments are not sufficient, the research significance is not explained enough, the purpose is not clear enough, and the hypothesis is not well presented.

Answer: suggestion accepted-

Physical preparation operation to decompress soils can be used opportunistically to incorporate correctives [13]. Suggested that if a tillage operation was used to incorporate limestone to the depths where soil pH restriction occurs [14]. This soil preparation used to incorporate limestone, would promote favorable conditions for the growth and development of crops, contributing positively to the volume of soil explored by the roots [15], infiltration [16] supply and cycling of nutrients [17].

Evaluating the feasibility of improving subsurface acidity using residual (undissolved) limestone and to test whether deep plowing and incorporation can correct subsurface soil acidity, observed that the use of a rotary hoe to a depth of 0.25 m significantly increased soil pH, and the deep incorporation of 6 Mg ha^-1 of limestone to a depth of 0.45 m with a rotary hoe also increased pH and decreased toxic aluminum [21].

Assessing the relative productivity of grains, determined by the combined analysis of four crops (soybeans, corn, beans and wheat) in three years of agricultural production, noting that the direct planting system involving subsoiling and application of additional lime on the surface and scarification treatment, promoted higher crop yields over the three years of evaluation compared to the direct planting system without mechanical intervention [25].

Assessing the subsoiling at 0.4; 0.60 and 0.80 m depth, concluded that the subsoiling tested in the study presented efficiencies proportional to the profile disturbance gradient, improving the root environment, evaluated by attributes that describe the dynamics and distribution of water in the soil profile [26].

Hypothesis

Therefore, it is hypothesized that the incorporation of limestone in depth with the use of the subsoiler will provide greater development of the root system along the soil profile, with a consequent increase in the plant’s ability to absorb water and nutrients, resulting in an increase in soybean grain productivity.

There is no distribution image of the research area, and the local climate conditions and soil characteristics should be given more accurately.

Answer: suggestion accepted- It is possible to observe that there was an accumulated rainfall of 850 mm, with an average temperature of 26°C, during the period of conducting the experiment for the 2019/2020 harvest and 745 mm, with an average temperature of 23°C, during the period of conducting the experiment for the 2020/2021 harvest.

Why is Figure 2 only applicable to the treatment of T4 and T3, and why are other treatments not provided, and the characterization effect of this figure is not significant.

Answer: suggestion accepted- Dual-function implement, used in the experiment, which decompact the soil (subsoiling) and the limestone by gravity behind its rods, up to 60 cm deep.

The expression of the unit is incorrect, for example, line 135, line 186, ha-1

Answer: suggestion accepted-

Line 111, missing unit, layer of 0-20,20-40, what units, cm?

The evaluator probably did not pay attention, however, the measurement unit in “cm” is already included in the second line of the table.

The meaning of ‘-m’ in Figure 5c?

Answer: suggestion accepted-

What’s ‘a’ and ‘b’ in Table 2, Table 3?

The letters a and b are used to demonstrate the statistical differences between the means, where means followed by the same letter do not differ from each other using the Tukey test.

The discussion part is not deep enough.

Answer: Suggestion accepted according to the text highlighted in the paper returned as an annex.

The citation is not correct in the manuscript, especially for the discussion part.

Answer: Suggestion accepted according to the text highlighted in the paper returned as an annex.

Conclusion is hasty and insufficient, besides, only one paragraph is recommended.

Answer: suggestion accepted- The superficial application of the oxide increases the mineral nutrition of plants, the production components, and the productivity of soybeans. There is agronomic feasibility for using the subsoiler to incorporation limestone.

Kind regards!!

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript study the subsoiling operation combined with the application of soil acidity amendment on the nutrition and productivity of soybean, these studies can be applied to the production of soybeans and have important application value. However, the Introdction is inadequately elaborated，particularly about the negetive effort of soil acidification and the acidity origin；2.3.1 should be 2.3.2, AND the descripition should be more concise.

Moreover, the data analysis was too simple, there would be more if the correlation analysis is added, the manuscript may be more meaningful and in-depth.

Author Response

We emphasize that all corrections/suggestions were taken into account and greatly contributed to improving the quality of the article. We greatly appreciate the opportunity to publish in this renowned journal. FOLLOW THE RESPONSES IN ACCORDANCE WITH THE CORRECTIONS/SUGGESTIONS HIGHLIGHTED BY THE REVIEWERS: REVIEWER 2:1. The manuscript study the subsoiling operation combined with the application of soil acidity amendment on the nutrition and productivity of soybean, these studies can be applied to the production of soybeans and have important application value. However, the Introdction is inadequately elaborated，particularly about the negetive effort of soil acidification and the acidity origin；2.3.1 should be 2.3.2, AND the descripition should be more concise.Answer: suggestion accepted- The authors agree with the reviewer's observations and sought to insert some more information to meet what was requested.

Moreover, the data analysis was too simple, there would be more if the correlation analysis is added, the manuscript may be more meaningful and in-depth.

For the initial analysis of the data in this article, the authors consulted a statistics specialist who initially recommended correction analysis, principal component analysis and the Tukey Test. However, after further study of the completed analyses, it was suggested that only the Tukey Test should remain, since the correlation and main components analyzes did not present information that would help in understanding and explaining the results.

Kind regards!!

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript investigated subsoiling and lime incorporation to improve soybean production in acidic soils. This is a worthwhile experimental aim, particularly as subsoil acidity is difficult to manage. It is difficult for readers to assess the level of acidity as the methods are not presented in full. Reference to standard Brazilian methods with no summarised details, when the methods are in Portuguese, is too opaque for an English language international journal and must be corrected prior to publication. For example, most 1:5 soil:CaCl2 extractions would have a critical pH near 4.7-4.8, which would indicate marginal levels of acidity if this is the method used, if the soil:solution ratio is lower however, perhaps the acidity is significant. The results suggest yield depression and response to liming, so one guesses that acidity is a constraint. However, readers should not have to guess such basic information. Brazilian methods are also flawed with respect to measuring CEC in my experience, as they record 'H+' that is not really present until the method is applied (i.e, it is an experimental artefact). Within Brazil, these consistently incorrect methods do allow producers and scientists to make practical management decisions, because of their extensive, and professionally undertaken, use. However, they do make it challenging to present results in an international context. The authors are encouraged to present a summary of the methods used for international readers so that they can draw conclusions in context.

The results seem to indicate limited effects, with lime addition having a positive effect - through N and S responses. The yield differences however are quite minor and no evidence is presented that subsoiling is worth the expense. The economics of the intervention would ideally be presented and compared against the limited benefits - that would then quantify the value of the intervention appropriately. If the results are as presented the conclusions would then be adjusted to reflect the limited benefits.

The explanations are simplistic and rather unlikely. The results suggest that improved S nutrition is associated not with 'increased organic matter' but with increased mineralisation and release of S. Marginally improved nodulation where surface liming occurred likely improved N nutrition. When stepping back and considering the actual results, all that happened was standard liming responses were observed, and nothing is contributed to the scientific literature. Perhaps if the authors dug trenches and measured the area of improved pH a significant and valuable contribution to the literature would occur as that is the key gap with these interventions, and is independent of the disappointing, but expected, plant responses. Most of the presented, non-significant, responses could safely be removed.

Comments on the Quality of English Language

Incomplete proofing throughout, Figure 3 for example, but otherwise a competent English presentation.

Author Response

The manuscript investigated subsoiling and lime incorporation to improve soybean production in acidic soils. This is a worthwhile experimental aim, particularly as subsoil acidity is difficult to manage. It is difficult for readers to assess the level of acidity as the methods are not presented in full. Reference to standard Brazilian methods with no summarised details, when the methods are in Portuguese, is too opaque for an English language international journal and must be corrected prior to publication. For example, most 1:5 soil:CaCl2 extractions would have a critical pH near 4.7-4.8, which would indicate marginal levels of acidity if this is the method used, if the soil:solution ratio is lower however, perhaps the acidity is significant. The results suggest yield depression and response to liming, so one guesses that acidity is a constraint. However, readers should not have to guess such basic information. Brazilian methods are also flawed with respect to measuring CEC in my experience, as they record 'H+' that is not really present until the method is applied (i.e, it is an experimental artefact). Within Brazil, these consistently incorrect methods do allow producers and scientists to make practical management decisions, because of their extensive, and professionally undertaken, use. However, they do make it challenging to present results in an international context. The authors are encouraged to present a summary of the methods used for international readers so that they can draw conclusions in context.

Answer: suggestion accepted- The summary of the methodologies used to determine the chemical attributes of the soil are described below:pH: Measurement of the effective concentration of H⁺ions in the soil solution, electronically, using a combined electrode, immersed in a soil suspension: 0.01 mol L^-1 CaCl₂ solution in a ratio of 1:2.5.

Calcium, Magnesium and Aluminum: Exchangeable Ca and Mg are extracted by KCl 1 mol L^-1 extracted together with exchangeable Al, titrating, in a fraction of the extract, aluminum with NaOH, in the presence of bromothymol blue as an indicator. In another fraction of the extract, calcium and magnesium are titrated by complexometry with EDTA, using eriochrome black-T as an indicator. In a third aliquot, calcium is determined by complexometry with EDTA and calcon carbonic acid as an indicator.

Hydrogen + Aluminum: Extraction using calcium acetate based on the buffering property of the salt, resulting from the presence of acetate anions. With the pH set ate 7.0, it extracts much of the soil’s potential acidity up to that pH value.

Phosphorus, Potassium, Sodium and Micronutrients: The Mehlich 1 extracting solution consists of a mixture of HCl 0.05 mol L^-1 +H₂SO₄ 0.0125 mol L^-1. The use of this solution is based on the solubilization of these elements by the effect of pH, between 2 and 3, with the role of chlorine being to restrict the readsorption process of newly extracted phosphates [29]. For micronutrients, the soil: extract ratio used was 1:5, while for the other elements it was 1:10 [30].

Sulfur: extraction of sulfate by phosphate ions (500 mg P/L) dissolved in 2.0 mol L^-1 acetic acid and subsequent quantification of available S by measurement in a spectrophotometer [31].

Organic Matter: The determination of the amount of organic matter was carried out by oxidizing it to CO₂ by dichromate ions, in a strongly acidic medium.

The results seem to indicate limited effects, with lime addition having a positive effect - through N and S responses. The yield differences however are quite minor and no evidence is presented that subsoiling is worth the expense. The economics of the intervention would ideally be presented and compared against the limited benefits - that would then quantify the value of the intervention appropriately. If the results are as presented the conclusions would then be adjusted to reflect the limited benefits.

Answer: suggestion accepted- After three years of applying the soil corrector (2002, 2004 and 2010), liming increases the supply of organic matter to the soil, through the addition of biomass, in variable amounts according to the crop, growing season and soil deoth. The application significantly increased total organic carbon at all depths, 10-20 and 20-40 cm [43].

3.0 The explanations are simplistic and rather unlikely. The results suggest that improved S nutrition is associated not with 'increased organic matter' but with increased mineralisation and release of S. Marginally improved nodulation where surface liming occurred likely improved N nutrition. When stepping back and considering the actual results, all that happened was standard liming responses were observed, and nothing is contributed to the scientific literature. Perhaps if the authors dug trenches and measured the area of improved pH a significant and valuable contribution to the literature would occur as that is the key gap with these interventions, and is independent of the disappointing, but expected, plant responses. Most of the presented, non-significant, responses could safely be removed.

Answer: The reviewer suggests that trenching into the soil should have been undertaken to map the area of improved pH along the profile.

Answer: 24 trenches were opened in the experimental area, where in each one the pH and calcium and magnesium content were evaluated in a stratified manner from 0 to 80 cm deep (vertical) and 80 cm wide (horizontal). However, due to the large amount of information, it was decided to present this information separately in another scientific article, which will soon be submitted for publication.

Kind regards!!

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been revised as recommended. Still some issues should be adressed before publication. Too many paragraphs in M&M part , futher emerge them. Footnote is recommended for tables.

Author Response

Dear,
Below is the article with the corrections suggested by the reviewer in the M&M item. The
Reviewer requested that some paragraphs be added to this item, and this recommendation
was accepted as can be seen in the paper returned with the Word correction tool activated.
We also emphasize that after the first round of review, the authors submitted the article
to a careful review of the English language, using the service of a company specialized
in translations and review of scientific articles. The authors carefully checked the need to
maintain the references used and concluded that they are all essential for the paper.
Kind regards!!