Phosphorus Dynamics in Stressed Soil Systems: Is There a Chemical and Biological Compensating Effect?

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have done a study with a nice idea of interaction study of different P levels with that of microbial population. The overall planning is good, however there could be some of the points that could further improve the quality of the manuscript-

(1)    What was the rationale behind choosing the four sets of soil microbiome, have you adopted from any published literature?

(2)     Kindly mention the corresponding P levels in kg ha^-1

(3)    In experiment 2, the 40 mg per kg of P correspond to how many pp, of available phosphorus?

(4)    Does the soil in treatment- P= 0 mg kg^-1 not have any available phosphorus? Or have naturally available phosphorus, but you have not added anything while experimenting?

(5)    If the soil with 0 mg per kg P is not devoid of any available P, then reduction in mycorrhiza colonization is questionable. The reason could be something else.

(6)    Have you checked available P in these soils?

(7)    Table1: Please add statistical analysis

(8)    Table 2: How the gene abundance was calculated? If it is compared from the copy number of a housekeeping gene, then should be analysed in any non-parametric method

 

(9)    Table 3: Use factorial analysis. All the data used in this study have more than one factor, thus consider factorial analysis  

Author Response

We thank you very much for your revision. In the following sections, you will find our responses to each of your points and suggestions. We are grateful for the time and energy you expended on our behalf.

 

(1) What was the rationale behind choosing the four sets of soil microbiome, have you adopted from any published literature?

We have added the criteria that we have used for choosing the four sets of soil microbiome in the material and methods section, which was already referenced a published literature in the manuscript (numbered 37).

 

[37] Arruda, B., et al., Manipulation of the soil microbiome regulates the colonization of plants by arbuscular mycorrhizal fungi. Mycorrhiza, 2021. 31(5): p. 545-558

 

(2) Kindly mention the corresponding P levels in kg ha^-1.

This information is already mentioned in the material and methods section as:

 

Experiment 1

“After the microbiome was established, P fertilizer triple superphosphate (TSP; 45 % soluble P₂O₅) was applied at rates of: 0, 20, 40 and 60 mg kg^-1, corresponding to approximately 0, 40, 80 and 120 kg ha^-1 of P₂O₅.”

 

Experiment 2

After the microbiome was established, P fertilizer triple superphosphate (TSP; 45 % soluble P₂O₅) was applied at rates of: 0, 20, 40 and 60 mg kg^-1, corresponding to approximately 0, 40, 80 and 120 kg ha^-1 of P₂O₅.

 

(3) In experiment 2, the 40 mg per kg of P correspond to how many pp, of available phosphorus?

We kindly ask for the reviewer to clarify the request, what pp means?

 

Did the reviewer mean ppm (parts per million). If so, the authors understand that the unit mg kg^-1 is equivalent to ppm, and so this information is already in the manuscript.  

 

Regarding to the availability, we have mentioned this information in the material and methods section, with the percentage of soluble P₂O₅ added based in the fertilizer guarantee as:

 

“P fertilizer triple superphosphate (TSP; 45 % soluble P₂O₅)”

 

(4) Does the soil in treatment- P= 0 mg kg^-1not have any available phosphorus? Or have naturally available phosphorus, but you have not added anything while experimenting?

The authors understand that the soil naturally present P content. In the present study, the treatments are regarding to the P input as described throughout the manuscript i.e.:

 

Experiment 1:

After the microbiome was established, P fertilizer triple superphosphate (TSP; 45 % soluble P₂O₅) was applied at rates of: 0, 20, 40 and 60 mg kg^-1, corresponding to approximately 0, 40, 80 and 120 kg ha^-1 of P₂O₅.

 

Experiment 2:

After the microbiome was established, P fertilizer triple superphosphate (TSP; 45 % soluble P₂O₅) was applied at rates of: 0, 20, and 40 mg kg^-1 of P, corresponding to approximately 0, 40, and 80 kg ha^-1 of P₂O₅.

 

Therefore, the treatments used in the manuscript are related to the P addition (applied P / P input) of 0, 20, 40 and 60 mg kg^-1, but not to the soil P content.

 

(5) If the soil with 0 mg per kg P is not devoid of any available P, then reduction in mycorrhiza colonization is questionable. The reason could be something else.

Despite the natural P is not 0 mg kg^-1, the P content is very low for the plant requirements and mycorrhiza dynamics, as presented on table 1, where in the treatment with 0 P input reached values of 0.86, 2.95 and 3.92 mg kg^-1 of P_AER for the soil microbial community treatments AS, NH80 and NS, respectively.

 

(6) Have you checked available P in these soils?

The available P were assessed using resin as extractor and the values are already presented in table 1 (before cropping), table 3 (after cropping with brachiaria) and table 4 (after cropping with crotalaria), as P_AER.

 

Additionally, we have remarked this information in the material and methods section as:

 

The soil samples were air-dried and analyses of available macro and micronutrients were performed [39]:

 

(7) Table1: Please add statistical analysis

The statistical analysis used on table 1 was descriptive, as mentioned in the material and methods section.

 

Additionally, we have added the statistical criteria used in the material and methods section, to make it clear.

 

(8) Table 2: How the gene abundance was calculated? If it is compared from the copy number of a housekeeping gene, then should be analysed in any non-parametric method

For biological parameters (bacteria qPCR and fungi qPCR) parametrical statistical analysis were used, applying the gamma regression model with the following models: i) null model (intercept only), ii) without interaction and iii) with interaction, as indicated by the Akaike Information Criterion (AIC), which was used to select the most suitable model, by using Student's t-test (p ≤ 0.05), as already mentioned in the manuscript.

 

(9) Table 3: Use factorial analysis. All the data used in this study have more than one factor, thus consider factorial analysis  

All the statistical analysis considered a factorial design, as described in the material and methods section:

 

Experiment 1:

The initial step of the first experiment was stablished in a factorial design (4 × 4), with eight replicates, totaling 128 experimental units.

 

Experiment 2:

Based on the results obtained in the first experiment, this second experiment was performed in a factorial design (3 × 3), with four replicates, totaling 36 experimental units.

 

Additionally, the results considered the factorial design, as presented on the tables, differentiating the factor as:

 

Different uppercase letters within the same row show significant differences among P doses by Student's t-test (p ≤ 0.05). Different lowercase letters within the same column show significant difference among microbial community by Student's t-test (p ≤ 0.05).

Reviewer 2 Report

Comments and Suggestions for Authors

The article with the title Phosphorus Dynamics in Stressed Soil Systems: Is There a Chemical and Biological Compensating Effect? Is very interesting and well written.

The study aim was to assess the interaction between soil, plants and microorganisms’ in soil with different microbial communities and different fertilizer rates based on phosphorus.

The only thing I would like to be improves is the statistics on table 3. Please add in the table note at the end what upper case show and what lower case show regarding statistics to be more clear and in the materials and methods too.

Congratulation to the authors

Author Response

We appreciated your constructive alteration outlined below and we tried to respond it in order to clarify the point.

 

The only thing I would like to be improves is the statistics on table 3. Please add in the table note at the end what upper case show and what lower case show regarding statistics to be more clear and in the materials and methods too.

 

The table 3 already presented a note with the required information:

 

Different uppercase letters within the same row show significant differences among P doses by Student's t-test (p ≤ 0.05). Different lowercase letters within the same column show significant difference among microbial community by Student's t-test (p ≤ 0.05).