Effects of Different Organic Fertilizer Substitutions for Chemical Nitrogen Fertilizer on Soil Fertility and Nitrogen Use Efficiency of Foxtail Millet

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 The manuscript is about using organic fertilisers and using less synthetic fertilisers. It uses a field experiments, crop and soil analyses to see the effects. The idea to use different fertilizers to obtain a better soil quality, and by doing so, a higher yield or a higher quality, has been studies in a huge amount of papers, and is still interesting. In this case the authors use “homemade fermented mealworm manure”.

However, the introduction is not good. It is not scientific, and it reads like a leaflet or advertisement. In science readers expect that both sides of an issue are described. Also the introduction contains much vague language, and the citations are not always good. The definitions of Nitrogen use efficiency are not clear. But worser, I get the impression the authors have use the wrong definitions. They have substituted the N fertilizer from urea by organic N fertilizers, but have not accounted this N.  The experiments are not very suitable to see an effect of different fertilizer: the difference between no fertilization CK), and full fertilization (N) on crop is very small. This means that the soil still can deliver much N, and effects of fertilizer N can hardly be seen. The authors should at least have used a synthetic fertilizer at the similar N rate as the organic N fertilizers. By comparing the findings of the organic N fertilizer (at a low N rate), and the synthetic fertilizes (at 100% N rate) you -almost per definition- that the organic fertilizer is more efficient.  

Vague language.

Detailed comments

1 “nitrogen reduction combined with organic fertilizer” The title is misleading or unclear. Organic fertilzers also contain nitrogen.

18 “hm2” What is hm2? Please use SI units.

22 “reduced…soil solid phase” What do you mean?

23 “soil quality”. What do you mean? This can be anything.

31 “conventional” What is conventional? Do you mean use of animal manures, or only use of synthetic fertilisers or both but no special fertilisers such as bio-organic of mealworm manure?

35 ”nitrogen bias productivity”. What is this? Do you mean base?

35 “rationing treatments”. What do you mean?

35 “agronomic utilization of nitrogen fertilizer”. It is unclear if you mean the synthetic N fertilizer, organic N fertilizer or both.

44 “shanxi”, please help the reader by stating that this is a province of China.

44 “miscellaneous grains”, unclear, what do you mean

45 “current crop structure adjustment”, I really have no idea what you are writing about

46 “strategic reserve crop”, vague, what do you mean. The product can be stored well?

47 ”millet after hulling millet” ??

48 “extremely valuable”. As gold, or diamonds, ore do you mean something else?

53 “is not always better”. Please be more precise. You probably mean: it is less effective, or more losses etc. Is it above normal fertilise advice values?

53 “not only destroys soil structure of cultivated land, reduces the content of organic matter….” Lots of very bold statements, that are certainly back up by science, at least not or the whole world. Please be more precise, and accurate.

Please also consider that in most cases studies synthetic fertilisations give less loss of soil organic matter than no fertilisation. See meta analysis of Ladha et al 2011   https://doi.org/10.2134/jeq2011.0064

58 “activate nutrients”. What do you mean?

66 “a large number of studies…” Which studies, you do not cite a meta analysis. You might cite: Wei et al 2021 https://doi.org/10.1016/j.envpol.2021.118176

72 “alleviate the negative ecological effects”. This is all very unprecise. The negative effects may be related to excessive use, not to the the fact that it is inorganic or organic. \also excessive use of organic fertilisers causes many problems. In fact in the EU there is a strict limit on animal manure of 170 kg N/ha, and a the limits on mineral fertilizers are crop and country specific and much higher. So it is certainly not a simple as you write.  

75 “20-30% nitrogen reduction combined with organic fertiliser” I guess you mean less synthetic N fertilizer and more N from manure.

I think the description of literature is not correct, and has been written much better in meta analysis. Both meta-analysis of Wei et al 2021, and Ren et al 2022 are rather clear on this point: Wei et al 2021 https://doi.org/10.1016/j.envpol.2021.118176. https://doi.org/10.1016/j.scitotenv.2022.158064.  Also it is not always true. Organic inputs have not resulted in additional yield in European long term experiments.  https://doi.org/10.1007/s11104-016-3031-x.

100 “dryfed millet” What is this?

104 “Jungu 21 as experimental materal” What is this. You mean the plant used for testing

119 “calcareous brown”. I have never heard of this soil classification. Please use international soil classification.

123 Table 1. Which chemical analyses have been used for total N, available N, P and K?

125 “bio-organic fertilize” It is complete unclear what this fertilizer is made of: Peat, animal manure, crop residues, waste from food industry, compost ? How can someone repeat this research if you do not provide the most basic information?

129. “homemade fermented mealworm manure” It is unclear how the fertilizer is made. How should someone repeat this experiment without the most basic  knowledge.

139 “adopted”, I guess you mean used.

134-137. You use “heavy superphosphate”, and “potassium chloride”. What is “heavy superphosphate”? In which experiment did you use both fertilizers? In line 144 you only state  that the organic fertilizers “are insufficient”. So did you add superphosphate and potassiumchloride to get equal amounts of N, P and K.

139-147 The set-up is horribly unclear. “nitrogen reduction 25%” What do you mean? 4109 kg x 1.46% N= 60 kg N. Do you mean by 25% reduction that you use 25% x240 = 60 kg less N from urea or only substitute N from urea by N from the organic fertilizer? So how much fertilizer did you use in N25A1: 180 kg N from urea + 60 kg N from bio-organic fertilizer, or do you use 25% less: 120 kg N from urea + 60 kg N from bio-organic fertilizer? Etc etc

Please. If I read a 25% reduction, and you use 60 kg N from an organic fertiliser, that reads like 75% reduction compared to 240 kg N from urea. It is horribly unclear what has been done.

157-163 this text is written as a guide, in future: “, and remember m1”. Please adjust.

182 “Z is the soil sample gas ..” I cannot read z in the formula.

235 “production volume and its constituent factors”. I wonder, do you mean yield? Strange use of English.

242 “dry matter accumulation”.??

244 “baked to constant weight”. Not correct English

245  “called its dry weight”??

254 “nitrogen uptake in the control area”. Unclear, what is this?

268. Circumstances are not clear. Did you use machines on the fertilized plots? Have the same machines used on the unfertilized plots, even without fertilizing?

277 and 483 “more conducive”. Improve English.

Table 2. Please do not only give symbols (Pt% etc.) but explain the measurements.

Table 3. Please explain X, Y and Z.A reader should be able to read the table without searching the whole text.

Table 5 The differences are rarely significant. The effect of N fertilizer is very small. This means that you have no performed a proper experiment. To see effects of N fertilizers the advice is find N application rates in which you can find a proper yield increase: an effect. At these rates you can use alternative fertilizers. This advice for proper experiments is given for example in: Schils et al 2020. https://doi.org/10.1002/9781118921487.ch5-1. They advice that “FRVs should be established in the following order of preference: 1. field experiment with appropriate response curves for both reference fertilizer and manure”. In this experiment you should have use moderate N fertilization levels, also for the reference fertilizer, in this case urea.

508-536 4.1 Do you really think that you determine such effects? There are long term experiments of 50 years in which they have not been able to show effects.

I stop here.

Comments on the Quality of English Language

see above

Author Response

Dear reviewer:

Thank you for carefully reading our manuscript and for your comments and suggestions. In the following, we have responded to your comments point by point. In the revised manuscript, all changes are highlighted in red.

1. We have changed the title of the article to Effects of different organic manure substitution of nitrogen fertilizer on soil fertility and nitrogen use efficiency of foxtail millet.
2. We have checked and changed the units throughout the text
3. Soil mass and moisture refers to soil mass moisture content, sorry, this is a mistake in our translation
4. Conventional fertilizers are the amount of chemical fertilizers applied alone by local growers
5. Nitrogen bias productivity refers to the ratio of crop yield after N fertilizer application to the amount of N fertilizer applied. It is an important indicator reflecting the combined effect of local soil base nutrient levels and fertilizer application.
6. In conjunction with treatment meaning organic fertilizer replacing chemical fertilizer, we have amended the text to read organic fertilizer replacing
7. Nitrogen fertilizer agronomic utilization is a combination of both organic and inorganic nitrogen fertilizers, and all fertilizer utilization indicators in the text are based on total nitrogen applied.
8. We have amended the text to read Shanxi Province, China
9. Mixed grains were meant to be coarse grains, which was a mistake in our translation.
10. We have amended the misrepresentation in the preamble.
11. Strategic grain reserves are those that stabilize the grain market and respond to situations such as major natural disasters or other emergencies.
12. Grain hulled as millet, which we have modified
13. For very valuable read nutritious
14. Not always better We have shown the dangers of applying chemical fertilizers in large quantities.
15. Nutrient activation refers to the activation of nutrients in the soil
16. We have cited the literature from the meta-analysis at https://doi.org/10.2134/jeq2011.0064
17. "Dry-fed millet" has been modified.
18. Jingu 21 This is the variety of grain we use.
19. We have modified to sandy loam.
20. The method of determination in Table 1 is the same as in 2.4.2, which we have modified.
21. Bio-organic fertilizers are fermented from 70 per cent chicken manure and 30 per cent crop residues, as described in the text.
22. Methods of making fermented yellow mealworm manure have been described in the text.
23. The tense in the text has been changed to the passive voice.
24. The experiment maintained a consistent total application of pure Nitrogen, Phosphorus and Potassium (NPK) across the treatments, with double superphosphate and Potassium Chloride used to make up the shortfall of Phosphorus and Potassium (KCl) after organic fertilizer substitution.
25. The description of the experimental design has been modified and the amount of fertilizer applied to each treatment has been explained in the form of a table.
26. Adjustments have been made to "and remember m1".
27. The formulas in the text have been modified.
28. Yield and its constituents modified to yield and its components
29. Nitrogen uptake in the control area is the aboveground nitrogen uptake of the nitrogen application treatments.
30. All treatments in the paper were consistent in their field management, except for the fertilization programme.
31. All tables in the text have been annotated.
32. The total N application in this experiment was based on previous research in the laboratory, where this N application gave the highest yields when chemical fertilizers were applied alone. We set up the organic fertilizer substitution on this basis for comparative trials.

Reviewer 2 Report

Comments and Suggestions for Authors

Abstract: Please focus the abstract on the scientific results with in-depth analysis of numerical values rather than reporting general finding.

Introduction:

- Argument is not clear stated in the introduction session. I would suggest the author to enhance the theoretical discussion and arrives the debate or argument. 

- The necessity and innovation of the article should be presented to the introduction.

Methodology:

- Please revise your methodology with passive sentences.

 Results and Discussion:

- It is suggested to compare the results of the present research with some similar studies which is done before.

Reference:

The citing information at the References section is given in a messy way, since it seems that the format not standardize. Therefore, unification of all citations has to be given, making them easily traceable by the readers. 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

** The manuscript needs language, grammar and syntactic editing. The English language usage should be checked by a fluent English speaker.

Author Response

Dear reviewers:

Thank you for carefully reading our manuscript and for your comments and suggestions. In the following, we have responded to your comments point by point. In the revised manuscript, all changes are highlighted in red.

1. We have made changes to the summary.
2. We have made additional refinements to the foreword.
3. We have made grammatical changes throughout the text.
4. We have streamlined the results and discussion of the article and compared them with the studies of others.
5. We have made various changes throughout the text.

Reviewer 3 Report

Comments and Suggestions for Authors

The Abstract should be shorter.

The Introduction is very general.

Table 1 - it is necessary to describe the methods by which the soil was analyzed. What does organic matter mean? How was it determined? Is it just the amount of organic carbon?

It is necessary to put Chapters 2.2 and 2.3 in a table to make it clear.

Chapter 2.4.1, on the other hand, does not need to be described in such detail (it is a standard method).

Results: Notes are missing under most of the tables.

The results are unnecessarily wordy. What is expressed in the table should not be repeated at length in the text.

Discussion: Again, this is very general. The already mentioned information is repeated.

I recommend combining the Results and Discussion sections. It is essential to shorten and make these chapters clearer significantly.

The conclusion again only repeats the results found.

You need to change the entire concept of the article. The article is very long and general. It is necessary to be more specific and highlighted.

Author Response

Dear reviewer:

Thank you for carefully reading our manuscript and for your comments and suggestions. Below, we respond to your comments point by point. In the revised manuscript, all changes are highlighted in red.

Changes were made to the summary.
The introduction has been condensed and expanded.
The soil analysis methods in Table 1 are supplemented by organic matter content. Materials derived from organic carbon content * 1.724.
Method simplification in 2.4.1.
Necessary annotations have been added to the figures and tables in this article.
The Results and Discussion sections have been simplified by removing duplicate descriptions.
The conclusion is summarized.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have made proper clarifications about the definitions, and add a table with the fertilization scheme. The previous text was incorrect and suggested that the used reduced amounts of nitrogen, but know I can read that the used the same total amounts of nitrogen. This shows that my previous comments were not correct. Therefore, my most important objection to this manuscript is gone. 

I think the authors do not give a proper discussion of the data. The yield is lower when using the organic N (treatment A2 and B2) instead of the mineral N but the authors seem to neglect the most important finding. The conclusion becomes better if one is more neutral.

Detailed comments to 2^nd manuscript.

Abstract: why not conclude that the organic fertiliser did not work well? The conclusion seems very selective. Urea normally has a rather high loss via NH3, and if another fertilizer gives less yield (N50A2 and B2 in comparison to N) then one should present this finding.

Title and abstract: The original “nitrogen reduction” has been removed, and replaced by “replacement” and in another sentence by “substitution”. That is quiet something different. Please use one term. The Keyword: “nitrogen fertilizer reduction” is incorrect, it is only reduction of mineral or synthetic fertilizer.

“as the first coarse grain”, what do you mean? Did it arrive in China at a certain date, or do you mean it is the best, or is I the most grown coarse grain? Please be more clear. Not everybody knows what coarse grains are.

The introduction still is one-sided: for example: “Organic fertilizer is rich in organic matter and various nutrients required by crops; it can not only provide nutrients for crops but can also promote the transformation of soil minerals; activate nutrients in soil; improve soil fertility and structure; effectively alleviate a series of cultivated-land-degradation problems, such as soil acidification, decreased organic matter content, and reduced soil microbial diversity in China; and contribute to the sustainable production of farmland ecosystems”. It is fine to state such things (please add references for somewhat bold statements) but then I expect that you also state the negative aspects of organic fertilizers.

I think “activation” of nutrients is not a scientific term. I would prefer a well known term as “bioavailable”.

“bio-organic fertilizers are fermented from 70…” What types of crop residues? To repeat the research, or make comparisons you should try to be precise and complete.

2.4.6 I miss the normal definition for nitrogen nutrient use efficiency.

NUE of organic fertiliser={(N uptake (treatment organic fertiliser) – N uptake (control))/total N added fertiliser} /{(N uptake (treatment urea) – N uptake (control))/total N added fertiliser}.

This will result in negative values for the organic fertilizer.

2.5 Which test has been used after ANOVA to give the significant differences: all the letters behind the average values in all the Tables? Bonferoni, Tukey, fisher’s protect etc. The choice makes a large difference. Therefore all the tables, and figures, should have LSD’s or SE’s per column or graph !

Table 2. Add dry weight or fresh weight.

“X is the soil’s solid phase, Y is the soil’s liquid phase, and Z is the soil’s gas phase”. Please add the word:  fraction. Also in the text this has been omitted. I also think a reader must be able to read a table without these explanation. Why not just write: solid fraction, liquid fraction, gas fraction? Also in Table 3 and 4 you use symbols instead of words. Please add also the name.

Table 5. NO-N should be NO3-N. Please use subscript for 3 in NO3 and 4 in NH4.

Table 6. You still use hm2. Please use SI units.

Table 6. Strange habit of showing all these digits that make no sense: 2432.70 ± 123.34. Why not write 2432 ± 123, or rather 2.43 ± 0.12 ton/ha. That is much easier to read, and makes sense.

Table 6. I miss a column with total N uptake by the crop (above soil parts), and nitrogen uptake in grain, while the definition for NRE uses these values.

Table 6. The indices need some very critical discussion. The production in the unfertilised control (CK) in 2021 and is higher than the fertilized treatments N50A2 and N50B2 (both years). This means that the nitrogen from fertiliser is not available, and even results in less available N for the crop.

Abstract, paragraph 3.6 & 4.2 & 4.4 and in chapter 5 “Effects of nitrogen reduction ..". There is no reduction, just substitution!!

Comments on the Quality of English Language

see above

Author Response

Dear reviewers:

Thank you very much for your response, we have refined the article based on your guidance. In the following, we have responded to your comments point by point. In the revised manuscript, all changes are highlighted in red.

1. We have added to the summary, results and discussion the results and reasons why the application of large amounts of organic fertilizer reduces grain yields.
2. We have standardized the use of "substitution" throughout the text.
3. The phrase "as the first coarse grain", meaning the earliest coarse grains grown, has been modified in the text.
4. We have added the negative impacts of organic fertilizers to the introduction and added references.
5. We have changed activation to bioavailability.
6. We have added comments below each table.
7. We have annotated table 2 to indicate that all organic fertilizers used are fresh weight.
8. We have modified it to subscripts
9. We have modified to international units and added aboveground and seed N uptake
10. We have modified the unit
11. We have revised the discussion section and added references.

Reviewer 3 Report

Comments and Suggestions for Authors

Materials derived from organic carbon content * 1.724. - Describe it in the article (for example, Organic matter = Cox * 1.726). By the way, this multiplication factor is nonsense.

Looks better than before.

Author Response

Dear reviewer:

Thank you for carefully reading our manuscript and providing your comments.

We have added "Organics derived from organic carbon content* 1.724" to the article, which has been highlighted in red.