Ecological Management of the Nitrogen Cycle in Organic Farms
Round 1
Reviewer 1 Report
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 1 Comments
Author response,
Thank-you for the review of this manuscript and for the valuable comments and suggestions.
Point 1. No specific examples related to the subsistence farming are provided. I observed this trend in most of the text. I would suggest the author to include some examples of research performed specifically in subsistence farming.
Response 1
RE: Subsistence farming focus,
Several studies from research on subsistence farms were included in the text of the original manuscript, but it was not always clearly stated that the research was conducted in subsistence or small farms of the tropics. A clarification was added, in the text to indicate that the cited research was conducted on subsistence farms (Refs. No. 77 & 80 & Line 444 of Revised version).
An additional section (Section 8, Line 820) was added to the text to provide a perspective on the management and understanding of the N cycle on subsistence farms.
The following citations, relevant to subsistence and small-scale farm of the tropics were already included in the original version of the manuscript, but it was not clarified that they were based on subsistence or small-scale farms of the tropics, For example (Note: Citation numbers based on the Original version of the manuscript),
Use of legumes as N source, [94, 109] (On revised version Nos., 106, 132)
Integrated systems and grass legume mixtures [20, 132, 134, 136, 142] (On revised version Nos., 20, 172, 174, 176, 182)
Modeling [64]
N cycle, [48]
Subsistence ag references, [9, 13, 123, 131, 145, 149 (and several others) (On revised version, 9, 13, 160, 171, 198, 200)
Agroforestry [19, 48, 88, 124, 127, 132, and 4 others) (on revised version 19, 48, 126, 161, 164 and others).
Point 2. Check across the text, sometimes says “N” and others “Nitrogen”.
Response 2.
Done.
Point 3.
In addition, no information related to how soil incubation could be used to improve management of nitrogen by modeling the potential nitrogen minezalization in subsistence / organic farming. Please add your vision in how this could contribute to the N management.
Response 3.
Additional comments were added with suggestions of modeling for subsistence and organic farms. (Lines 302-305)
Point 4.
I wonder if the author is considering organic and subsistence farming as similar / related farming systems. Seems some subsistence farmers are using organic amendments such as manure, however, also mentions previous experiences of organic farming in France. Is the farming system in France organic and subsistence? Please clarify.
Response 4.
The manuscript is focused on organic farms, but indicates that many subsistence farms in the tropics rely on little or no external inputs. Organic farms may be capital intensive, but subsistence farms have limited access to capital, for the purchase of external inputs.
A clarification was added in the text to indicate that most agricultural research on N cycles has been conducted in temperate areas, followed by conventional ag, organics, and the least, on subsistence farms (Lines 825-830).
Point 5
Maybe reorganizing the paper in 2 parts (within the same article). One related to the organic farming/amendments and nitrogen cycles and finalizing with a revision of specific cases on subsistence farming.
Response 5
A section was added (Section 8, Line 820-835) to briefly review the prospects for Subsistence Agriculture, with respect to possible management practices to manage the Nitrogen cycle.
Point 6
Line 362-364: you mentioned that nitrate might be leached if its release is not synchronized with the crop uptake. I wonder if you found a way to synchronize the release and the uptake, because the way the sentence is written seems to show some lights to solve this problem.
Response 6
Additional text was added to suggest management practices to minimize leaching potential (Lines 379-381]
Point 7
Lines 394-396: add a reference specially for the symbiotic relations with cereal crops.
Response 7
References were added, as suggested (Line 419 and References 34,112 & 113).
Point 8
Conclusions. Could it be possible to state some specific measures to improve the problem specifically in subsistence farming?
Response 8
A section was added in the text (Section 8) to briefly review the prospects for Subsistence Agriculture, with respect to possible management practices to manage the Nitrogen cycle. A Table was also added to indicate some management practices followed to manage the N cycle in subsistence agriculture (Section 8 & Table 4, Lines 820-864).
Point 9
What would be the main differences between the nitrogen cycle in organic production in the tropic versus organic production in a Mediterranean weather? Is there more information (less gaps) in the nitrogen cycle when is researched in a Mediterranean weather? Asking because you mentioned that “considerable knowledge gaps thus exist with respect to N cycling in organic systems, especially for the tropics”
Response 9
While similar N cycle mechanisms presumably exist under organic systems in temperate areas and tropical regions, considerable more research has been conducted in temperate regions, and thus less is know about the N cycle in tropical regions. Additional comments were added in the text on Section 8 to clarify this point (Section 8, Lines, 825-830).
Thank-you again for the review of the manuscript and for the valuable comments and suggestions.
end of comments
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Reviewer 2 Report
The work deals extensively with the issue of nitrogen cycling in the organic system. It discusses a number of processes affecting the content and availability of nitrogen in the soil for plants, from the point of view of both the supply of nitrogen, increasing its mibilility and preventing the formation of nitrogen losses in crop production. the work emphasizes the primary role of soil health and microbial activity in the soil as factors directly affecting the availability of nitrogen. It discusses a number of nitrogen-containing products, such as manure, legumes, etc., and presents opportunities to increase nitrogen mobility for plants. The paper presents and explains in detail the basic parameter determining the correctness of nitrogen management (nitrogen use efficiency). I evaluate the presented work correctly, the content is completely related to the topic of the article.
Below are my notes and comments on the manuscript.
1. What is the main question addressed by the research?
The manuscript provides a literature review of the elements of nitrogen management in an organic system, highlighting the potential for nitrogen supply opportunities on the farm, the mechanisms and processes responsible for its distribution in the soil. Elements of the nitrogen cycle in the soil-fertilizer/nitrogen source-plant system are discussed. Attention was paid to the quantitative possibilities of nitrogen supply in the organic system and, on the other hand, the possibilities of the most optimal use of nitrogen were presented. The fact that the nitrogen fertilizer advisory system needs to be refined in the organic system for better nutrient utilization was also emphasized.
2. Do you consider the topic original or relevant in the field? Does it
address a specific gap in the field?
The content of the manuscript addresses the very important issue of nitrogen management in an organic system as well as organic farming practices can be implemented in other crop production systems. The issue discussed in the manuscript is of particular importance for understanding the essence of nitrogen management as one of the main most limiting factors of crop production in an organic system determining the potential of humanity's organic food supply
3. What does it add to the subject area compared with other published
material?
The paper highlights the role of the release rate of nitrogen-containing nutrients in proper plant nutrition in an organic system. The paper could present various figures as examples of nitrogen release dynamics for plants during vegetation. Ways of increasing the rate of nutrient use efficiency (NUE) were suggested. Emphasized the role and importance of species breeding as an element of increasing NUE. The intercropping system was stressed as a solution for N lack, different strategies was presented as a tool that limit N losses.
4. What specific improvements should the authors consider regarding the
methodology? What further controls should be considered?
The paper could provide examples of different nitrogen sources for plant fertilization and their mineralization rates and effects on crop yields, How much different fertilizer sources contain organic soluble nitrogen?
5. Are the conclusions consistent with the evidence and arguments presented
and do they address the main question posed?
The role of the closed nitrogen cycle was emphasized in the conclusions, which indicates that the final conclusions are relevant to the topic.
6. Are the references appropriate?
The provided literature list is adequate to the topic of the paper on nitrogen management in an organic system
7. Please include any additional comments on the tables and figures.
No tables or graphs are presented in the paper. Supplementing the work with charts and graphs would have increased the quality of the manuscript, and would have made it easier to understand nitrogen transformation and its complex nature in organic agriculture. In addition, the lack of tables reduces the quality of the work, in favor of having to find the data described in the text. Compilation of the presented literature review in a table would have facilitated the analysis of the problem of nitrogen management in production in organic agriculture.
Author Response
Response to Reviewer 2 Comments
Point 1
The paper could provide examples of different nitrogen sources for plant fertilization and their mineralization rates and effects on crop yields, How much different fertilizer sources contain organic soluble nitrogen?
Response 1.
Thank-you for the review of this manuscript and for the valuable comments and suggestions.
The text was amended as follows to provide additional information on organic soluble N sources,
“Organic amendment applications alone are often not sufficient to meet N requirements during peak crop demand periods, and so their use is often complemented with high soluble N organic fertilizers such as fish or feather meal, or with leguminous crop residues which are also high in soluble organic N [34].” (Lines 314-318)
Three Tables were included in the manuscript to profile important organic fertilziers/amedments and to highlight some of the legume and agroforestry species used as N sources, and their respective N mineralization rates.
Point 2.
No tables or graphs are presented in the paper. Supplementing the work with charts and graphs would have increased the quality of the manuscript, and would have made it easier to understand nitrogen transformation and its complex nature in organic agriculture. In addition, the lack of tables reduces the quality of the work, in favor of having to find the data described in the text. Compilation of the presented literature review in a table would have facilitated the analysis of the problem of nitrogen management in production in organic agriculture.
Response 2.
As suggested, four tables were added to the manuscript providing examples of N content and mineralization of several organic amendments; Profile of some cover cover crops common in organic farms, and N contributions; Percent N content of several agroforestry species; and a sample of studies conducted under Subsistence agriculture (as recommended by Reviewer 1). Tables 1-4.
Point 3
The paper could provide examples of different nitrogen sources for plant fertilization and their mineralization rates and effects on crop yields, How much different fertilizer sources contain organic soluble nitrogen?
Response 3
Three tables were added to provide a profile of some organic fertilizers/amendments and mineralization rates; a Table with the N content of some leguminous crops; and the N tissue content of some agroforestry species. An additional table was included (based on suggestion by Reviewer 1) with details of management practices pertinent to subsistence farmers in the tropics. The presented C/N ratios and reported mineralization rates indicate the relative rates of N release over time.
Point 4
In addition, the lack of tables reduces the quality of the work, in favor of having to find the data described in the text. Compilation of the presented literature review in a table would have facilitated the analysis of the problem of nitrogen management in production in organic agriculture.
Response 4
Thank-you for the suggestion. Four tables were added to the manuscript, as suggested, to highlight important sources of Nitrogen, and their mineralization rates, for organic and subsistence farmers.
Thank-you again for the review of the manuscript and for the valuable comments and suggestions.
End of comments
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Round 2
Reviewer 1 Report
Dear author, thank you for your hard work in improving the article.
