Variation of Soil Nitrogen, Organic Carbon, and Waxy Wheat Yield Using Liquid Organic and Mineral Fertilizers

Round 1

Reviewer 1 Report

Author Response

Reviewer 2 Report

The article entitled "The Influence of Liquid Organic Fertilisers on the Variation of Nitrogen and Organic Carbon in Clay Loam Cambisol and on Winter Wheat Yield" evaluate the effect of organic fertilisers, as anaerobic digestate and pig slurry, on the dynamics of SOC-N and grain yield.

The idea of studying the reuse of by-products or wastes as organic fertilizers is interesting and has practical significance. However, there are several problems with this manuscript. The analysis of the research topic is not sufficiently thorough. The study of some fundamental parameters is missing. Furthermore, research studies like these require medium-long term investigations. Two years to evaluate particular dynamics such as those related to carbon or nitrogen are not enough.

The manuscript needs to be enriched and corrected. Overall, the paper cannot be accepted.

Some problems are listed below:

Title:

- The title should be rewritten. It is long and unattractive.

Introduction:

- This section is not very interesting. In the first part, there are many known topics and, above all, there are no bibliographical references (lines 30-35). To make it pleasant to read, data such as those related to the use of organic liquid fertilizers in your country - region can be added.

Materials and methods:

-Section 2.1:

Bibliographic references about some methods of analysis are missing;

There is no constant and complete characterization of soils. Parameters such as pH and phosphorus (related to all theses and all sampling periods) can be fundamental for the discussion of the results.

-Section 2.3:

Specify the WEOM extraction methods;

It is appropriate to define precisely what is meant by mobile humic acids and the respective extraction method.

- Section 2.5:

Which statistical test was used to verify the data normal distribution and the homogeneity of variances?

Results:

- It is recommended to delete Section 3.1. It is more appropriate to report these data when the authors present the results in the following paragraphs;

- In tables 3, 4 and 5 and in in all figures the letters relating to significance are missing.  In this way, the understanding of the results is more difficult;

- In the manuscript, the authors refer to the microbiological characteristics of the soil (lines 378-379, 553-555). Has any analysis been conducted in this regard?;

- Line 305-306: this sentence is not clear. What is mean by an inconsistent trend?;

- The authors in line 306 write "a pronounced increase in N tot during the period of intensive winter wheat growth (2020 IG)". Since the statistical analysis is not shown in the respective table, it is difficult to notice a pronounced increase. It would seem moderate;

Has any analysis been carried out on the wheat plant (carbon and nitrogen)? The study of the translocation might help to understand some results;

The section numbering is not correct;

The units of measurement must not be in the background of the figures but on the axes.

Section 3.3.1:

- The sentence in line 329-331 must be deepened and correlated with data. High molecular weight compounds are not always humic substances. Reference number 38 contains no such a statement!

- Did the authors investigate the qualitative aspects of WEOC and humic acids? Analysis such as fluorescence and FTIR could be very useful for evaluating the dynamics of these important parameters.

Some interesting results were not considered by the authors. For example, WEOC content in thesis "N60" during the winter wheat growing season.

The authors in line 432-433 assert that "In the first year of fertilizer application, the soil C: N ratio remained essentially unchanged". Figure 5 does not show this trend.

Discussions:

This section needs to be rewritten because it has many critical issues. It is usually not recommended to repeat the results obtained. To make this section more interesting, more references to other similar research should be included. I appreciate what has been done, but it is not enough. The response to many dynamics of the parameters studied is always attributed to the weather conditions. I believe that the results obtained can also be supported by other explanations.

I also suggest not to give definitive explanations if it is not possible to demonstrate them with the results obtained.

Finally, the sentences in lines 577-581 express doubts reported at the beginning of the review report.

The discussion of the article is not sufficient to support the interesting results of this article. Many explanations are untenable.

Conclusions:

They are missing completely.

Recommendation: Do not publish

Author Response

 Dear Reviewers and Editor,

We are grateful for valuable advice on how to improve the quality of our manuscript.

We edited the manuscript regarding all reviewers’ recommendations, detailing our changes presented in the tables below. The latest version of the manuscript uploaded to the system has been corrected using “Track Changes”.

Thank you for your time

With respect,

The authors

Author Response File: Author Response.docx

Reviewer 3 Report

Dear Sir,

 Greetings!

Thanks for invitation to review the manuscript entitled “The Influence of Liquid Organic Fertilisers on the Variation of Nitrogen and Organic Carbon in Clay Loam Cambisol and on Winter Wheat Yield “.

 The paper might be considered in the journal the following are the suggestion from my side.

#Use specific one Keywords: liquid anaerobic digestate; pig slurry; ammonium nitrate; waxy winter wheat; water extractable organic carbon; soil organic carbon; mobile humic substances; mineral nitrogen forms; total nitrogen; C:N ratio; grain yield

##Revised However, the balance between soil organic matter mineralisation and synthesis is being disturbed, leading to a decline in soil organic matter. Carbon (C) sequestration and an increase in SOM have a direct positive effect on soil quality and crop yields. Organic carbon leads to improved soil structure and particle aggregation, ensures moisture retention, is associated with im- proved supply and uptake of plant nutrients, promotes micro-organism activity in the rhizosphere [1–4], and regulates greenhouse gas emissions, thereby contributing to cli- mate change mitigation [5].

## Revised the reference [28,29,22],

## Revised the sectioned Spectrophotometric quantitative measurements of N-NH4 and N-NO3 in liquid ferti- lisers were done using Hach-Lange cuvette tests (LCK 302 and LCK 339) and spectropho- tometer DR 3900 (Hach Lange, Germany). The concentrations of soil N-NO3 were deter- mined by the potentiometric method in a 1% extract of KAl(SO4)2×12H2O (1:2.5, w:v), and soil N-NH4 using spectrophotometric measurement at a wavelength of 655 nm in a 1M KCl extract (1:2.5, w:v).

## Merge the fig Figure 2. Variation of soil water extractable organic carbon (WEOC) (0–30 cm) during winter wheat growing season effected with different nitrogen rates (A), fertilisers (B) and their interactions (C). Standard error (SE) of the mean was used to represent

## Figure 6. Principal components analysis (PCA) loading plot for PC1 and PC2 scores. Analysis was conducted using data  of soil and grain yield characteristics when waxy winter wheat grown in 2021 using 3 type fertilisers (AN – ammonium  nitrate, PS – pig slurry, LD – anaerobic liquid digestate) and different nitrogen rates (0, 60, 120, 120+50 kg N ha-1). Used  data set was from 3 time per year collected soil.

## Use proper citation style no need to repeat citation style.  Water extractable organic carbon is found in soil leachate [48] and has high degrada- bility, therefore, the variability in its concentration is primarily determined by seasonal weather conditions [49] and average annual rainfall [48]. It is suggested that application of N fertilisers does not affect the leaching of organic carbon, nevertheless, it may increase organic N leaching [50]. According to the literature, mineral N content in soil is increased more by digestate than by mineral NPK fertilisers. The use of straw as a fertiliser in com- bination with digestate can increase N immobilisation and at the same time reduce the N- NH4 content in soil [51]. The effect of digestates on soil biology is poorly understood, alt- hough half of the literature has indicated a neutral effect of biogas digestates on soil mi- crobial quality [52]. Barłóg et al. [51]

## Put in table format 1. Control (N0); 123
2. N60 mineral fertiliser – ammonium nitrate (AN60); 124
3. N60 pig slurry (PS60); 125
4. N60 liquid anaerobic digestate (LD60); 126
5. N120 mineral fertiliser – ammonium nitrate (AN120); 127
6. N120 pig slurry (PS120); 128
7. N120 liquid anaerobic digestate (LD120); 129
8. N120 ammonium nitrate and N50 ammonium nitrate (AN120+50); 130
9. N120 pig slurry and N50 ammonium nitrate (PS120+50); 131
10. N120 liquid anaerobic digestate and N50 ammonium nitrate (LD120+50).

 Rest things are quite ok

Thanks much

Author Response

 Dear Reviewers and Editor,

We are grateful for valuable advice on how to improve the quality of our manuscript.

We edited the manuscript regarding all reviewers’ recommendations, detailing our changes presented in the tables below. The latest version of the manuscript uploaded to the system has been corrected using “Track Changes”.

Thank you for your time

With respect,

The authors

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Authors,

considering the revisions made, the manuscript has greatly improved and I believe it is ready for publication. I suggest you review the paragraph numbering. There are still two paragraphs 3.2.1.

Best regards

Reviewer 3 Report

 The paper could be considered now changes are satisfactory