The Effect of Sulfur Carriers on Nitrogen Use Efficiency in Potatoes—A Case Study

Round 1

Reviewer 1 Report

Dear Authors 

See attached my comments. 

Comments for author File: Comments.pdf

Author Response

Thank you for your valuable comments.

1. The introduction has been redrafted as suggested. The chapter has been supplemented with literature data on calcium sulphate (in relation to yield-promoting action) and data on nitrogen fertilization in relation to nitrogen rates and growing conditions. Specific items of literature have been added, but the mentioned matters have not been elaborated on due to the restricted volume of this chapter. The interaction of nitrogen and the sulfur carriers in other crops has also been indicated. Nitrogen management (shaping efficiency) has not been removed from the paper due to the title of the article. According to the authors, this part is important.
2. ‘The tests were carried out in four replications’ – added to the article.
3. The conclusions have been redrafted/shortened, removing some references to specific research results. The conclusions were too detailed, indeed.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript (MS) is addressing the question how the sulphur application in two different forms can affect the potato yield and some calculated nutrient use efficiency. It is a crucial question nowadays to get such studies, due to the environmental and economic impact of fertilizers. The study produces a very detailed work, of considering several calculation factors and produce data on the annual efficiency for the yield. The MS is well-written and provide useful information for the potential readers.

Figures and Tables are very demonstrative; however, some minor correction is required.

Table 1: It is somehow missing, how was the Ca-content in soil? Regarding that sulphur was added as elemental and as CaS, perhaps it is an important information about the Ca content in soil, as well.

The pH of soil was rather low at each of the years, and it is a very good aspect of showing details about it in relation with the changes in Ca-content at Result part, subchapter 3. In case of so low pH, it is crucial if sulphur need to be applied at all, or not. The authors were demonstrating the interrelation with N-fertilizer doses and the necessary of proper application doses.

Fig.6: does not containing all of the necessary legend, i.e. the TY and EA should be mentioned here, as well, even though it is already known from other sources. All figures and tables should be understood independently from the text, in general.

Fig 9: Please check the Legend and clarify the mistakes: The figure does not contain some of the elements. …And also, TUS can be either Total sulphur or also Unit sulphur, as it is written.

Summarizing the opinions, the study can be published after minor modifications.

Author Response

Thank you for your valuable comments.

1. The calcium content in the soil during the experimental period was not investigated and therefore such data is not included in Table 1. However, the authors have soil analyses from the area where the experiment was located. The assessment carried out by the Mechlih 3 test clearly shows a low calcium content in the soil. In the discussion chapter, this matter is indirectly touched upon, explaining the effect of calcium introduced with one of the carriers.
2. With regard to the low pH – the experiment was carried out in slightly acidic soil. Theoretically, it should be a little higher, but the truth is, the cultivation of potatoes is unfortunately carried out in soil with a pH of about 5.5. Therefore, the properties of an experiment location are a compromise between the optimum conditions and reality.
3. The keys in Fig 6 and Fig 9 have been corrected

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript by Potarzycki and Wendel investigated the effect of sulfur carriers on nitrogen use efficiency in potato, which has great meaning for improving potato production. However, this manuscript has some drawbacks in the Methods, Discussion, and Conclusions parts, the comments are listed as follows:

1. Line 107-109, the authors stated that sulfur has an effect on many levels, among which the most important are: control of chlorophyll synthesis and photosynthesis efficiency, etc. However, why didn't the authors determine the chlorophyll content and photosynthesis of the plants in this study, since they are very important indicators for explaining the nitrogen metabolism influenced by the sulfur.

2. Line 176, since the mineral nitrogen content in the 0-90cm layer of the soil was 46 – 56 kg N·ha-1, how were the 0 and 30 kg N·ha-1 levels of nitrogen fertilization in the experiment achieved?

3. In the Methods part, the measurement methods of those nutrients content should be simply described.

4. The Discussion part is too lengthy, maybe the readers can not easily grasp the main ideas, it needs to be simplified. The authors should avoid the results reproduction in this part, it is better to improve this part by focusing the discussion on the mechanisms and main effects and causes.

5. Line 559, revise the water use efficiency to be water-use efficiency.

6. Line 561-562, what is the mean of the phrase "optimal rainfall distribution"? Can the authors give an exact explanation for this define in this study. Sometimes, strong rains will cause high flow and penetration of rainwater, which simultaneously lead to nutrients loss in the soil.

7. The Conclusions part should be simplified. Just focus on the main conclusions, no need to present the detailed results again here.

Author Response

Thank you for your valuable comments.

1. Indeed, in the presented work, no data on the efficiency of photosynthesis are given. The indicators (for example, SPAD) were studied, but their results will be published in another, upcoming article.
2. Fertilization rates in each treatment are considered as the amount introduced with fertiliser, regardless of the content in the soil. The nitrogen content of soil given in Table 1 is the baseline, the 'background', which is the same for all treatments.
3. A brief description of analytical methods has been added
4. Repetitions and descriptions of results were removed from the discussion, in order to make it shorter. We agree with the reviewer on this point. However, some data must remain in the paper for ‘discussion’ purposes and literature reference. In our opinion, the problems addressed in the article require a broad approach and consideration of various aspects.
5. Corrected according to suggestions
6. The sentence has been redrafted
7. The conclusions have been redrafted/shortened, some references to specific research results have been removed. The conclusions were too detailed, indeed.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The paper can be accepted in present form.