Effect of Fertilization on the Energy Profit of Tall Wheatgrass and Reed Canary Grass

Round 1

Reviewer 1 Report

Authors have evaluated in this study the effect of different fertilization on the energy profit of tall wheatgrass and reed canary grass. They have analyzed the effect on yields, higher heating value, energy profit and soil erosion. The manuscript presents interesting results of grass energy that can contribute in the environment. However, the manuscript presents a series of problem and authors should improve many points in different parts and explain well the results obtained and the conclusions. Following, I have included some comments aimed to enhance the paper:

• Rewrite the Abstract, it's a little confusing.
• The authors must include in the introduction more details of the objective of their study, as well as citing the other relevant methods used for the different fertilization used.
• I suggest to the authors to add a new section detailing state of the art. In this section, authors have to describe the relevant related work in which explain the grasses energy, advantage, contribution in soil erosion and environment. It is also important to cite also some results of the two species used.
• In the Table 1, authors must add the letters of the Tukey test for the same year, it is important to compare the effect of the treatment for each species in each year. Since the weather effect can affect from one year to another, within the same year and with the separation of groups, a better effect of fertilization can be observed, and if it is significant or not.

• All the legends of the figures and tables must be improved. They have little information. Add data used, variable with units, treatments ext …..

• The authors say in line 182 that yields of grasses in the Mineral and Digestate variants are very similar. It is necessary to analyze very well the values ​​from one year to another, for example in 2012, in RCG the yield increased from 2.4 with Mineral to 4.3 with Digestate (almost double). Authors must analyze well the significance within each year and the differences between fertilization on the one hand and control and fertilization on the other hand.
• In Table 5, authors must present the letters of separation of the groups. Table 5 is very saturated with a lot data, and not very readable. I suggest the authors to change it to histograms with group separation (Tukey letters) and significance (p values).
• In Table 6 we observed that there is a difference between Mineral and Digestate that authors have not mentioned and not explained, for example in 2017 for TWG from 161 to 133, in 2014 for RCG from 43 to 75. Authors must add more detail in discussion for these comparisons and all differences of their results.
• Comparisons with maize in the manuscript are very confusing and not clear in the text, restructure it.
• The PCAs are informative, but it is not reflected in the presentation of the results and their discussion. Authors must improve this part.
• Finally, the topic of this study is very interesting, but authors must restructure the manuscript to improve the readability of the text and their results and discussion.

Author Response

Dear reviewer, Thank you for your comments. The answers are in the attached file. Best regards, Marek Kopecký 

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript agronomy-1100485, entitled “Effect of Fertilization on the Energy Profit of Tall Wheatgrass and Reed Canary Grass” by Kopecký et al. deals about an interesting subject regarding the effects of fertilization management on tall wheatgrass and reed canary grass dry matter production. Moreover, the authors assessed the benefits from these crop/treatments in terms of heating value, energy profit and protection of soil from erosion. The manuscript is of good quality and I believe that the manuscript is of potential interest for readers of Agronomy and fall within its scope.  In general, the experiment seems to be well performed while the manuscript needs some small improvement before the publication.

I suggest to revise the keyword changing with a more effective word.

Materials and methods section is the part of the manuscript that need the most work. Please add more detail about the experimental setup. Add a specific sub-paragraph for statistical analysis. Specify the usle C factor for tall wheatgrass and reed canary grass.

Results and discussion are fine.

The conclusions are based on the results and give a satisfactory resume of the results achieved from the experiment.

In my opinion, the authors did not find any difference among fertilizer types and they try to assess some difference among systems by integrating a more comprehensive analysis of the systems by introducing calculations related to economic value and erosion. The authors shouldn't belittle their results because they found no differences between the two types of fertilizers. With this regards, they should consider some other aspects: 1) mineral and digestate fertilizer are in some aspects quite similar, because digestate contains a lot of mineral N (as ammonium) and P. Therefore, considering that did you balanced the mineral contribution between them, it may be reasonable that you did not find any differences between the treatments; 2) digestate is a byproduct not always accepted or easily disposed of in the fields and, therefore, you have provided a way for its correct valorization; 3) most important, the species did you tested are important for marginal lands and from some point of view a direct comparison with maize senseless. Focus your manuscript on this aspect, the valorization of marginal lands characterized by loss of fertility, especially due to erosion, by energetic crops as tall wheatgrass and reed canary grass. These my latest suggestions are not related to mandatory revision but are comments in order to improve the citability and impact of your article.

Finally, I suggest to revise some small language issues along the text.

My specific comments, that I hope will help the authors to improve the manuscript, are reported in the attached files.

Comments for author File: Comments.pdf

Author Response

Dear reviewer, Thank you for your comments. The answers are in the attached file. Best regards, Marek Kopecký 

Author Response File: Author Response.docx

Reviewer 3 Report

Overall, a very nice study that will be of great benefit to scientific progress in the field of the study of ecosystem services biomass provisioning (here, for bioenergy production) and erosion control. However, there are a few significant shortcomings in the current manuscript that need correction:

1) English must be improved significantly, it is not acceptable at the moment.

2) Table 5 is very extensive and yet does not contain the information I would expect, considering that it is a randomized small-plot experiment. Please point out the statistical differences between variants within years and between years within variants (e.g., using upper and lower case letters). 

3) From Abstract to Conclusions, the performances of RCG and Tall Wheatgrass to corn are presented. however, I cannot find any direct measurements either in terms of energy yield potential or for soil loss (erosion potential) for corn. Here the authors need to improve and explain in more detail a) how and when the yield potential for corn was measured, b) how and when the erosion potential for corn was measured. If information from previous studies has been used, this should be more clearly referenced.

4) In this context, please also check if all data are available or indicated according to the Data Availability Statement, which is missing in the study so far.

5) The authors focus on erosion mitigation through perennial energy crop but the authors do not refer to a highly cited study by Cosentino et al., 2015 (https://doi.org/10.1007/s12155-015-9690-2) entitled "Soil Erosion Mitigation by Perennial Species Under Mediterranean Environment" (please note, that I am not a co-author of that study). I strongly recommend considering the comparison of the results of this study with the study by Cosentino et al. 2015 and furthermore, to look for more references once again. I am sure this will help to improve the overall quality of the maunuscript even further.

Minor comments:

The format "HHV…higher" (L138-160) looks unsound. I suggest using  "HVV = higher" for all parameters mentioned in L138-160.

A patent is referred to (Section 5. Patents), but I cannot find any patents.

Author Response

Dear reviewer, Thank you for your comments. The answers are in the attached file. Best regards, Marek Kopecký 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have made all requested changes in the content of the resubmitted manuscript. However, after all modifications in the manuscript, authors must complete their resubmission with a full English review.

Reviewer 3 Report

Well done.