Impacts of Multi-Strategy Nitrogen Fertilizer Management on Potato Yield and Economic Gains in Northeast China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Correct the given changes. Shorten the abstract, results and discussion. Give tables of results on potato yield in different fertilization systems.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Thank you for your constructive suggestions. We have revised the manuscript carefully according to your comments. Please check the new version of the submitted manuscript. Regarding your comment to give yield data, we are unable to show it in the manuscript due to the volume of data and have provided it in the attached document.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors assessed potato yield depending on the dose of nitrogen fertilization. The results were based on research at 15 stations in a selected region in northeastern China.

 Comments on the manuscript:

• The disadvantage of the study is that it is based on only one ingredient (nitrogen), while it has been known for years, as the authors emphasize, that in potato cultivation it is also important to balance other ingredients, especially potassium

• The experimental scheme takes into account very large doses of nitrogen, up to 385 kg, whereas in sustainable agriculture nitrogen doses should not exceed 150-180 kg N/ha

• The results of many previous experiments conducted in many countries also indicate that the use of too high doses of nitrogen (above 200 kg/ha) is not justified both from the economic point of view and also from environmental protection reasons (penetration of nitrate nitrogen into groundwater)

• The authors conclude that the nitrogen dose at the level of 220-230 kg N/ha has a beneficial effect, but this is not confirmed by Figure 3. Doses above the L4 level no longer result in an increase in yield, but the increase in potato yield above the L3 dose (165 kg) is also not very large, about 2-3 thousand kg/ha

• The authors conduct their considerations generally in conditions of low potato yields; potato yield at the level of 2 thousand kg/ha due to the use of very high doses of nitrogen indicates factors other than nitrogen limiting the increase in tuber yield. In many countries, the recommended nitrogen dose is 40 kg N/ha per 10 tons of expected tuber yield.

• The comments presented do not reduce the fact that the manuscript was well prepared, however, the results of potato yields and cost calculations are of limited importance to the research area

• The study should be supplemented with basic information on potato agrotechnics, including the fight against pests and the use of other nutrients in potato fertilization.

Author Response

We thank you very much for your constructive comments and suggestions on our manuscript. We have revised the manuscript carefully according to the comments and have documented our answers below. Here is our point-to-point response.

1.The disadvantage of the study is that it is based on only one ingredient (nitrogen), while it has been known for years, as the authors emphasize, that in potato cultivation it is also important to balance other ingredients, especially potassium.

Response: Thank you for your comments. General supplemental N fertilization is very common in the daily field management of crops. In addition, N is also the main influence on chlorophyll for photosynthesis, which is important for potato growth and yield. Other constituents such as K are put in as basal fertilizers with relatively small crop requirements. This study presents an analysis of the most important factors affecting yield with the aim of identifying specific management practices for N fertilization.

2.The experimental scheme takes into account very large doses of nitrogen, up to 385 kg, whereas in sustainable agriculture nitrogen doses should not exceed 150-180 kg N/ha.

Response：In this study, the amount of nitrogen applied is compared to the control group, which means that we default to the control group not applying nitrogen fertilizer. As you said, the amount of nitrogen applied in sustainable agriculture is in terms of general soil fertility. The two are not in conflict and justify the dosages in this study side by side. In actual field management, the amount of nitrogen applied needs to be adjusted according to the local soil fertility.

3.The results of many previous experiments conducted in many countries also indicate that the use of too high doses of nitrogen (above 200 kg/ha) is not justified both from the economic point of view and also from environmental protection reasons (penetration of nitrate nitrogen into groundwater).

Response：Thank you for your consideration of the reasonableness of this study. Similar to the previous question, the N fertilizer dose in this study is theoretically relative to extremely poor soils and is not the amount of N applied that should be referenced in practice. Future research will need to further determine the true N application level based on the available soil N content. This study can serve as an important reference for factors affecting yield, cost, and economic gains.

4.The authors conclude that the nitrogen dose at the level of 220-230 kg N/ha has a beneficial effect, but this is not confirmed by Figure 3. Doses above the L4 level no longer result in an increase in yield, but the increase in potato yield above the L3 dose (165 kg) is also not very large, about 2-3 thousand kg/ha.

Response：Figure 3 demonstrates that the range of N application with the highest yield is L4-L7, i.e. 220-385 kg/ha, and not 220-230 kg/ha. Because the range of N application set in this study was discontinuous, with the aim of obtaining the approximate optimum range and exploring the mechanism of the effect of N fertilizer dosage on potato yield.

5.The authors conduct their considerations generally in conditions of low potato yields; potato yield at the level of 2 thousand kg/ha due to the use of very high doses of nitrogen indicates factors other than nitrogen limiting the increase in tuber yield. In many countries, the recommended nitrogen dose is 40 kg N/ha per 10 tons of expected tuber yield.

Response：Thank you for your professional comments. The potato yield was only 8000 kg/ha under the condition of no N fertilizer (CK2), and the yield could be more than 20000 kg/ha with the application of sufficient N fertilizer, which indicates that the amount of N fertilizer is an important factor affecting the potato yield, and shows the significance of this study. The explanation about the amount of nitrogen applied has been described in relation to question 2 and 3.

6.The comments presented do not reduce the fact that the manuscript was well prepared, however, the results of potato yields and cost calculations are of limited importance to the research area.

Response：Thank you for recognizing the manuscript. In China, especially in the main potato production areas, the area planted and the yield of potato are very important to farmers, and in addition, the cost is also of concern to them, as it is directly related to the final income. Reducing costs and improving yield are crucial to farmers' planting decisions and to the implementation of potato staple foods. Therefore, we believe that this study is of value to other countries in the world where potato is grown on a large scale.

7.The study should be supplemented with basic information on potato agrotechnics, including the fight against pests and the use of other nutrients in potato fertilization. 

Response：Thank you for your suggestions. Since the DSSAT model was used in this study to simulate potato yield, other nutrients were included in the input parameters of this model. Regarding pest and disease control naturally, they are not taken into account, and all other growth conditions were input according to the unified parameters.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

thank you for the opportunity to meet the manuscript entitled: "Impacts of Multi-strategy Nitrogen Fertilizer Management on Potato Yield and Economic Gains in Northeast China". The research was focused on maximizing the efficiency of N fertilizer utilization and solving the problem of increasing production but not increasing income.

I consider the combination of agronomic and economic indicators to be the most objective output for practice as a great benefit of research. The structure of the manuscript is at a satisfactory level and appropriate graphic elements are used, which increases its quality.

Comments:

In these types of studies, the heterogeneity of the conditions of the various areas in which the experiment is carried out is always a big risk. It is hardly possible to assume that the weather conditions or soil characteristics were the same in all areas. These two factors can greatly affect the production, but also the utilization of nutrients (mainly N).

The MM chapter lacks a description of the statistical methods used to evaluate the experiment. I recommend to supplement it.

Author Response

Thank you for your accurate description of the manuscript and your recognition of our work. Regarding your question about yield differences due to weather and soil variability at different locations, in section 2.3.2, the yield in this study was obtained by simulation with the DSSAT-SUBSTOR crop growth model, whose inputs include weather and soil data at different sites, which is basically sufficient for potato yield analysis at the current scale. As for the possible effects of variability at smaller scales will be considered in future studies. Thank you again for your comments and suggestions.