Soil Health Check-Up of Conservation Agriculture Farming Systems in Brazil

Round 1

Reviewer 1 Report

I enjoyed very much reading this article, since the topic covered and its potential application is of great interest. Generally, the manuscript is good, following an adequate structure and clearly exposing the results obtained. English is good and fluent; however, the authors should double check the writing as there are some typo and spelling errors.

What I believe could be considered the main areas were these manuscripts should improve are the following:

Firstly, I am missing what could be considered a “control” field/s; i.e. grain production fields that have never been manged under CA, to better contrast the results obtained in terms of soil enzymes and soil biodiversity analysis. This is a rather relevant aspect that can make a difference to this study. 

Secondly, it is important to justify your selection of soil enzymes. The introduction section gives a general explanation of these but does not show why are the one selected important; why are these relevant for the agroecosystems; and why can they be of special interest for CA. Other enzymes with similar significance and relevance could be used to point out other aspects of the dynamics of nutrients in soils and their bioavailability (Dehydrogenase, acid-phosphatase, protease, etc…)

            Thirdly, it would be convenient to explain why microbiome biodiversity was only analysed in 1 grain field and why was this specific one selected.

            And finally, other aspects need to be addressed like what is the time interval underlying in “long term” CA; Where do the criteria to differentiate yield environments come from; the fact that corn and soybean yield is not differentiated (when they have differential potential yield maximums; or why no statistical analyses were conducted to show the effect of filed and yield environment in all the variables shown in Tables 2, 3 and 4.

 

I hope these suggestions help to improve the work carried out.

 

 

Kind regards.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The current study entitled “Soil health check-up of Conservation Agriculture farming systems in Brazil” could very appropriate for Agronomy, yet I suggest a major revision due to the following concerns.

 

General comment

 

Be prudent: You mentioned huge areas of study. One of the main concerns in soil science is it spatial heterogeneity. To extrapolate conclusions over these areas you will need thousands of sampling points. You only have seven grain production fields. Therefore, your work is a good approximation, but its representativeness of the Brazil’s reality is very limited.

I found the general metrology a bit weak (the opposite of robust and neutral method).

 

Abstract

 

“Around 40% of the data points had low biodiversity and higher presence of plant-growth promoters suggesting the need for redesign of the CA farming systems management to obtain a living soil.” Please, rewrite the last sentence. I do not see the direct link between the ideas before and after “…suggesting the need…”

 

Introduction:

Avoid long sentences in order to facilitate communication.

In the second paragraph it is convenient to include more references

Would you please give a single line about the knowledge gap which your research has covered?

Please, declare your hypothesis before your aims.

Also, provide a novelty statement at the end of the introduction. What new things authors have done?

 

Material and Methods

 

 “The high yield environment (HYE) was classified as > 110% average crop yield in the field, the medium (MYE) as 80 – 110%, and the low (LYE) as < 80%.”

This looks a key decision in your research. Was this decision arbitrary?

Also, you should explain why the yields in table 4 do not match with these percentages.

 

Please, explain better the sampling points.  You wrote: “three replicates for chemical and enzyme activity analyses, totalling 63 georeferenced sampling points.” But then, you explained other different thing about the sampling points “Seven sampling points comprised one in the center of the crop row and three on each side of the row”

Also I do not know were “(54 soil sampling points)” come from (in point 2.3)

 

Why did you dry all soil? As far as I know, the soil samples for these two enzymatic activity usually is not dry and they can be stored in the fridge for a short period of time.

Please, include the reference about the use of 1.0 mol L−1 KCl solution and the use of HCl 0.1 mol L-1 as extractants

“One of the fields of the Aquarius project (S-2), that had a large available data base, was used to carry out soil DNA characterization” OK, but, Please, include if these samples were initially classified as H, M and/or L.

 

“The normalized differences in vegetation indexes (NDVI) near the soil enzyme sampling points were obtained using At farm® platform (Yara Ltda).” Please, provide more information.

 

Table 2. Remove the space between the mean and the standard error in S.

Also, you have to explain if ± is the standard error in the foot of the tables.

 

Results and discussion

 

In Agronomy as in most of the actual journals is strongly recommended to separate results and discussion. Please in Results apply a mechanistic approach as supporting evidence for the later discussion of results.

You have to used more references in the first part of your discussion in order to support your writing. Try to summarize your discussion and be focused in your main findings.

Table 4. Please, include the superscript (1 and 2) in the first row (¹ TN and TOC determined by d dry combustion method²; SOM determined by wet oxidation through the Walkley-Black adapted)

 

Table 5. Please, remove the row with “Brazil”. I think is inappropriate to extrapolate your results from seven grain production fields to the whole country.

 

 

 

You should complete your discussion a bit more. E.g. you explain why “In this study, the Ca2+ content had positive relationship with enzyme activity in the Central-West agro-ecoregion”. But, you did not explain why it was not shown the same trends in order fields.

Fig.2 c Please copy this figure with higher definition in your document

In some parts of the discussion, it looks more a general outreach article than a research paper. Therefore, it could be reduced and be more focused on introducing or discusses your specific researcher.

Fig. 3. In this figure, it looks that the different Agro-ecoregion influent the results much more than the type of yield environment (L, M, H).

“… the different yield environments by agro-ecoregions were distinguished which highlighted that LYE was different from HYE and confirmed that the use of this tool in precision agriculture is important for site-specific micro management in CA systems.” First, you can write this but inside each agro-ecoregion. Second, I think, in this case, we cannot write about precision agriculture with this intensity of sampling in each agro-ecoregion. I suggest being more cautious with your extrapolations

“Figure 5b shows that the β-glucosidase and arylsulfatase enzyme activity were efficient in distinguishing HYE and MYE from LYE” This is a key issue in your work… and I think it is not correct. Please, check again this figure.

 

Fig. 6. Remove “***p<0.001”

Where did this n=6 come from? Please clearly include in Material and Methods

Are they from S1 or S2 (as in Materials and Methods said)?

 

Conclusion

Start with a conclusive conclusion.

 

Please, take into account the previous comments. E.g. correct this sentence “the enzyme activity was an efficient tool to distinguish the low yield environment from the medium and high yield environment within the fields.”

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

 

The most relevant aspects that have not yet been addressed are:

• It is important to know how the authors have answer their point “it is important to know how this CA are being successful in maintain/improve soil health” if there is NO CONTROL treatment or no reference initial point. All the areas samples are from “ grain production fields distributed in four Statesthat have been managed under CA over the long-term” so there is no initial or reference to compare the results with. I still think this is quite an issue.
• The fact that corn and soybean yield is not differentiated (when they have differential potential yield maximums)
• why no statistical analyses were conducted to show the effect of field and yield environment in all the variables shown in Tables 2, 3 and 4.

 

I hope these suggestions help to improve the work carried out.

 

 

Kind regards.

 

 

Author Response

Response to R1 attached

Reviewer 2 Report

My mayor concer is about the "Results and discussion" section. However, I understand that sometimes is convenient to merge Results and discussion. 
Also, there are serveral small issues than have to be corrected in the "proof reading" before the publication e.g "with high pH water"

Author Response

Response to R2 attached

Author Response File: Author Response.docx