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Peer-Review Record

Mulching-Induced Changes in Tuber Yield and Nitrogen Use Efficiency in Potato in China: A Meta-Analysis

Agronomy 2019, 9(12), 793; https://doi.org/10.3390/agronomy9120793
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Agronomy 2019, 9(12), 793; https://doi.org/10.3390/agronomy9120793
Received: 20 October 2019 / Revised: 19 November 2019 / Accepted: 20 November 2019 / Published: 22 November 2019
(This article belongs to the Special Issue Soil Fertility Management for Better Crop Production)

Round 1

Reviewer 1 Report

The authors describe a meta-analysis of previous studies to understand the benefit of mulching practices and its effect on tuber yield and Nitrogen Use Efficiency. The study includes factors such as fertilization, tillage practices of China to gain an idea of the practices currently used and the effectiveness of these. It is an interesting approach to gain valuable information from a large pool of studies to provide advice to help Chinese farmers use effective growing practices and increase yield.

There are however several  issues that need to be addressed in the paper that might help gain more out of the study. The paper is data heavy, but does not provide sufficient interpretation with relevant literature on the topic in the discussion. Specific comments relating to the article:

All the graphs in general in the paper would benefit from having the titles included in the figures as they are very confusing in the current format. In the introduction line 43, the study introduces the importance of potato and describes the demand for the crop with a projection until 2020 with one study referencing it. A more long-term projection with more relevant references need to be included. Describe in a sentence or two what is mulching with key references to introduce the term to first time readers in line 53 . Good point is that the benefits of mulching are introduced well. Please rephrase the sentence in line 57-60 as the meaning is unclear. The Table 1 does not add any novel additional information to the paper. It is the same as what is described in the Reference 13 and does not need to be included. The manuscript would suffice with referencing the study. Line 168 the abbreviations for PFM, SM, PFSM should be included. It is not clear how the interpretation of the fertilizer use was derived in the study. Especially the reduction in synthetic K input by 100% in combination with mulching practices. Better justification is needed for the strong conclusion and interpretations. The interpretations and core focus of the study is in China. However, the study could have included a comparative analysis with other major potato growing regions of the world to see if the trend observed in this study with similar practices were comparable. This could have helped strengthen the conclusions of the study. In the introduction the paper describes the NUE of China to be only 20% of the world average. Inclusion of comparative analysis of other regions with better practices could have been included to determine the causes for the improved NUE compared to China and discussed critically. The discussion could be more critical and discuss the benefits of fertilizer use in addition to the practice of mulching The references section has a formatting error.

To conclude, I recommend that the paper should not be accepted for the publication in the present form. It can benefit from a more robust analysis to be more suitable for publication.  

Author Response

All the graphs in general in the paper would benefit from having the titles included in the figures as they are very confusing in the current format.

Authors’ response: We are grateful to the reviewer for this suggestion, we revised these graphs to address this suggestion.

 

In the introduction line 43, the study introduces the importance of potato and describes the demand for the crop with a projection until 2020 with one study referencing it. A more long-term projection with more relevant references need to be included.

Authors’ response: We are grateful to the reviewer for this suggestion, we added a reference to address this suggestion.

Potato (Solanum tuberosum L.) is one of the most important staple foods and the worldwide demand is expected to exceed that of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) by 2020 as its human consumption is increasing [1, 2]

International Potato Center, http://www.cipotato.org/pressroom/factsfigures/let them eat potatoes.asp, 2009.

Describe in a sentence or two what is mulching with key references to introduce the term to first time readers in line 53. Good point is that the benefits of mulching are introduced well.

Authors’ response: We are grateful to the reviewer for this suggestion, we describe mulching in detail (Line: 53-57).

Mulches, i.e. any material such as straw, leaves or plastic film, that is spread or formed upon the surface of the soil to protect the soil and/or plant roots from the effects of raindrops, soil crusting, freezing, evaporation, etc [8].

Please rephrase the sentence in line 57-60 as the meaning is unclear.

Authors’ response: We are grateful to the reviewer for this suggestion, we revised this sentence to address this suggestion (Line: 61-65).

Northwest China is an important potato planting zone, but tuber yield was severely threatened by water shortage due to low seasonal precipitation [16].

The Table 1 does not add any novel additional information to the paper. It is the same as what is described in the Reference 13 and does not need to be included. The manuscript would suffice with referencing the study.

Authors’ response: We are grateful to the reviewer for this suggestion, which we have followed.

Line 168 the abbreviations for PFM, SM, PFSM should be included.

Authors’ response: We are grateful to the reviewer for this suggestion, we added abbreviations for PFM, SM, PFSM in revised manuscript (Line: 188-190).

There were 1232 observations for plastic film mulching (PFM), 464 for straw mulching (SM), and 106 for combination of plastic film and straw mulching (PFSM).

It is not clear how the interpretation of the fertilizer use was derived in the study. Especially the reduction in synthetic K input by 100% in combination with mulching practices. Better justification is needed for the strong conclusion and interpretations.

Authors’ response: We are grateful to the reviewer for this suggestion, we revised the discussion section to address this suggestion (Line: 367-378).

When organic fertilizer was applied, application of K fertilizer significantly reduced the benefit of mulching on yield and NUE, indicating that K and organic fertilizers should not be applied simultaneously when mulching is used. This is likely that a lot of K is brought into the soil from organic fertilizer and under these conditions, thus excessive K fertilization, when organic fertilizer was applied, reduced the effect of mulching on yield and NUE as a result of. Under organic fertilization, mulching could save synthetic N and P fertilizer by 50%, and K fertilizer by 100% in potato production without affecting yield and NUE. The benefit of mulching and organic fertilization on yield and NUE was reduced under high application rates of N, P, and K, mainly because both mulching and organic fertilizer can improve the availability of these nutrients to plants [53-55]. Thus, under mulching, high N, P, and K fertilization, when organic fertilizer was applied, did not increase yield and NUE, in agreement with previous studies [15, 56].

The interpretations and core focus of the study is in China. However, the study could have included a comparative analysis with other major potato growing regions of the world to see if the trend observed in this study with similar practices were comparable. This could have helped strengthen the conclusions of the study.

Authors’ response: We are grateful to the reviewer for this suggestion, we added the information on the application of N rate in China in Materials and Methods section. NUE is compared between China and other countries in the world.

On average, the application rate of N fertilizer was 360 kg N ha−1 in China, for eight geographic regions (NE, NC, NWI, NWD, QT, MLYR, SW, and S), the application rate of N fertilizer was 228, 471, 330, 280, 300, 400, 300, and 390 kg N ha−1, respectively [33]. (Line: 136-138)

Mulching greatly increased potato yield and NUE, which is in agreement with the results from other studies [15-18]. NUE of potato was less in China than in other countries in the world (160−240 kg tuber yield kg1 N) [38-47]. This discrepancy may be associated to differences in the application rate of N, since some studies in other countries have been conducted at a low N rate (i.e., medium N rate, 100−200 kg N ha−1) [38-47]. (Line: 323-327)

In the introduction the paper describes the NUE of China to be only 20% of the world average. Inclusion of comparative analysis of other regions with better practices could have been included to determine the causes for the improved NUE compared to China and discussed critically.

Authors’ response: We are grateful to the reviewer for this suggestion, we have made a detailed analysis and comparison between China and other countries in the world (Line: 323-327).

Mulching greatly increased potato yield and NUE, which is in agreement with the results from other studies [15-18]. In China, potato NUE (160 kg tuber yield kg−1 N) was less than other countries in the world (170−200 kg tuber yield kg−1 N). This discrepancy may be associated to differences in the application rate of N, since in other countries, some studies have been conducted at low N rate (i.e., medium N rate: 100−200 kg N ha−1) [38-46].

The discussion could be more critical and discuss the benefits of fertilizer use in addition to the practice of mulching.

Authors’ response: We are grateful to the reviewer for this suggestion, we revised the discussion section to address this suggestion (Line: 362-367).

Fertilization significantly influenced the effect of mulching on yield and NUE of potato. Without organic fertilization, mulching was most effective at improving yield and NUE at application of synthetic N and P2O5 at rates of 100−200 kg ha−1 and K fertilization at 0−100 kg K2O ha−1, demonstrated that the right combination of N, P, and K fertilization rate is an effective means to increase tuber yield and NUE, in agreement with previous studies [15, 33, 38-47].

The references section has a formatting error.

Authors’ response: Thank you for this observation, we revised the references section.

Reviewer 2 Report

General comments

Thank you for the opportunity to review the paper. I now have a much better understanding of the impact of mulching treatments on potato production in China. I like the approach used in the paper as stated on lines 85-87 “Meta-analysis provides a formal statistical method to compare and integrate the results of multiple studies and reveal underlying factors contributing to responses and make inferences on regional and global scales”. I think overall, it is the right approach, and the work should be published. Well done to the authors for presenting the draft paper to Agronomy. However, several sections which need re-writing. I acknowledge these are minor corrections and are only suggestions to improve the readability of the paper and have no impact on the conclusion made by the authors.

My main concern is I had problems understanding the P fertilizer treatment due to the description used on lines 134–135 which states “synthetic nitrogen (N), and phosphate (P) fertilizers application rates were categorized as <100 kg ha−1, 100–200 kg ha−1, 200–300 kg ha−1, and >300 kg ha−1. Firstly, P in general applied at much lower rates than N but the same rate of N and P are presented due to N being stated in kg N ha-1 while P is stated in kg P2O5 ha-1. It would be better in the paper to use the same units ie kg ha-1 for N, P and K to improve the readability of the paper. Also, line 137–142 which refer to the use of organic fertilizers needs to be re-written to separate the N and P treatments. It currently reads as if P is a basal treatment whereas P is present later in the paper as a separate treatment.

Finally, please check the captions, so they are consistent with the Journal style.

Abstract

Lines 33−34: Please use the same fertiliser units throughout the paper. These lines use kg P2O5 and K20 ha-1. I would use kg N, kg P or kg K ha-1.

Line 33: I would rewrite the following from - “synthetic nitrogen (N) and potassium (K) fertilization was 100−200 kg P2O5 ha−1 and 0−100 kg K2O ha−1, respectively” to - “N applied was 0−300 kg N ha−1, P applied was 0−130 kg P ha−1 and K applied was 0−166 kg K ha−1“.

Introduction

The introduction reads well with good use of references to support the argument presented. The only comment I have is related to line 55: That is, I would have thought decrease leaching would result in increased salinity.

Material and Methods

Lines 111−112: re-write the following from – 1802 observations at 105 sites were compiled into the dataset. As not all studies reported potato yields along with NUE, the numbers of comparisons for yield and NUE were not equal. To – from 1802 observations at 105 sites were compiled into the dataset. As not all studies reported NUE, the numbers of comparisons for NUE were 1571.

Lines 118−122: Change to – QT, Qinghai and Tibet; NE, Northeast China, NWI, Northwest irrigation region; NWD, Northwest dryland region; NC, North-central China; MLYR, The middle and lower reaches of Yangtze River; SW, Southwest China; S, South China

Lines 126−127: Change the following - (1) PFM, plastic film mulching; (2) SM, straw mulching; and (3) PFSM, combination of plastic film and straw mulching.

Line 127: Please provide the type straw, for example, is it rice? Also, provide the nutrient content of the straw mulch.

Lines 131-132: Add FP and RFP as illustrated as follows: (1) straw and/or plastic film mulch on FP, flat plots; (2) straw and/or plastic film mulch on RFP, ridge-furrow plots.

Lines 133−135: Should the section read as follows - nitrogen (N) fertilizers application rates were categorized as <100, 100–200, 200–300, and >300 kg N ha−1, phosphorus application was categorized as <43, 43–87, 87–130, and >130 kg P ha−1 and potassium (K) fertilizer rates were categorized as 0, 0–83, 83–166, and >166 kg K ha–1.

I would use P and K instead of P2O5 and potash. I think it is better to use P and K to be consistent with using N. I also think the word synthetic is not required when referring to fertilizer.

I have converted 100–300 kg P2O5 ha-1 to 43–130 kg P ha-1 and 100–200 kg K2O ha-1 to 83-166 kg K ha-1. Perhaps it would be good to provide a comment on N, P and K fertiliser rates used on potatoes in China in the Materials and Methods section. That is paper presents fertilizer rates used in experiments. It would be helpfully for the reader to know the fertilizer rates used by growers.

Line 137: What are the organic fertilizers and their associated nutrient contents?

Lines 139−141: The statement reads as if the P was applied as a basal treatment? Please re-write the statement.

Results

In all figures: I think it would be better to remove the symbol from the error bars presented in the figures. Often the symbol is larger than the error bar.

Line 182: N fertilizer use efficiency (NUE) is stated on line 73. Please delete nitrogen use efficiency and just use NUE in the rest of the paper.

Lines 182−187: The caption does not reflect the presentation in figures a, b and c. Perhaps the caption could be changed to the following. The response of change in potato yield and NUE to mulching compared to no mulching average for China (a) and for the 8 regions for potato yield (b) and NUE (c). (Abbreviations: NC, North-central China; QT, Qinghai and Tibet; NE, Northeast China; NWI, Northwest irrigation region; NWD, Northwest dryland region; MLYR, The middle and lower reaches of Yangtze River; SW, Southwest China; and S, South China).

Lines 193−197: North China Plain region not stated in the regions in lines 118-122. Should it be North-central China?

Lines 210−214: Caption needs correcting because references to figures e and f are not included. Please edit caption with reference to these figures.

Lines 279-284: Please present phosphorus rates as P instead as P2O5.

Lines 290-295: Please present potassium rates as K instead as K2O.

Discussion

Lines 310−311. Need a statement on the timing of fertilizer applications in the Materials and Methods section for the different regions.

Reference

I have not checked the references used in the paper.

Author Response

All synthetic nitrogen (N), and phosphate (P) fertilizers application rates were categorized as <100 kg ha−1, 100–200 kg ha−1, 200–300 kg ha−1, and >300 kg ha−1. Firstly, P in general applied at much lower rates than N but the same rate of N and P are presented due to N being stated in kg N ha-1 while P is stated in kg P2O5 ha-1. It would be better in the paper to use the same units ie kg ha-1 for N, P and K to improve the readability of the paper. Also, line 137–142 which refer to the use of organic fertilizers needs to be re-written to separate the N and P treatments. It currently reads as if P is a basal treatment whereas P is present later in the paper as a separate treatment.

Authors’ response: Thank you for this observation. But we don't agree with this suggestion. Because in agronomy, the application rate of N fertilizer is stated in kg N ha-1, the application rate of P fertilizer is stated in kg P2O5 ha-1 and the application rate of K fertilizer is stated in kg K2O ha-1.

Also, line 137–142 which refer to the use of organic fertilizers needs to be re-written to separate the N and P treatments. It currently reads as if P is a basal treatment whereas P is present later in the paper as a separate treatment.

Authors’ response: We are grateful to the reviewer for this suggestion, we revised this sentence to address this suggestion (Lines: 151-153).

To study the effect of synthetic fertilizer application rate on potato yield and NUE, according to whether organic fertilizer is applying, the dataset was divided into two sub-datasets: (1) organic fertilization (O); (2) without organic fertilization (NO); meanwhile, synthetic nitrogen (N) and phosphate (P2O5) fertilizers application rates were categorized as <100 kg ha−1, 100–200 kg ha−1, 200–300 kg ha−1, and >300 kg ha−1; potash fertilizer (K2O) rates were categorized as 0, 0–100, 100–200, and >200 kg ha–1.

Finally, please check the captions, so they are consistent with the Journal style.

Authors’ response: Thank you for this observation, which we have followed.

All Lines 33−34: Please use the same fertiliser units throughout the paper. These lines use kg P2O5 and K2O ha-1. I would use kg N, kg P or kg K ha-1. Line 33: I would rewrite the following from - “synthetic nitrogen (N) and potassium (K) fertilization was 100−200 kg P2O5 ha−1 and 0−100 kg K2O ha−1, respectively” to - “N applied was 0−300 kg N ha−1, P applied was 0−130 kg P ha−1 and K applied was 0−166 kg K ha−1“.

Authors’ response: Thank you for this observation, but we don't agree with this suggestion. Because in agronomy, the application rate of N fertilizer is stated in kg N ha-1, the application rate of P fertilizer is stated in kg P2O5 ha-1 and the application rate of K fertilizer is stated in kg K2O ha-1.

The introduction reads well with good use of references to support the argument presented. The only comment I have is related to line 55: That is, I would have thought decrease leaching would result in increased salinity.

Authors’ response: Thank you for this observation. In field experiment, the amount of N fertilizer leaching loss is very large, thus reducing N uptake efficiency and subsequently resulting in a low NUE. Mulching can reduce N fertilizer leaching loss, enhance plant N uptake and then improve NUE. So far, there is no report that reducing N leaching around the root zone will increase soil salinity.

Lines 111−112: re-write the following from – 1802 observations at 105 sites were compiled into the dataset. As not all studies reported potato yields along with NUE, the numbers of comparisons for yield and NUE were not equal. To – from 1802 observations at 105 sites were compiled into the dataset. As not all studies reported NUE, the numbers of comparisons for NUE were 1571.

Authors’ response: We are grateful to the reviewer for this suggestion, which we have followed (Lines: 117-121).

169 publications (17 in English and 152 in Chinese) from 1802 observations at 105 sites were compiled into the dataset. As not all studies reported NUE, the numbers of comparisons for NUE were 1571.

Lines 118−122: Change to – QT, Qinghai and Tibet; NE, Northeast China, NWI, Northwest irrigation region; NWD, Northwest dryland region; NC, North-central China; MLYR, The middle and lower reaches of Yangtze River; SW, Southwest China; S, South China.

Authors’ response: We are grateful to the reviewer for this suggestion, which we have followed (Line: 128-133).

According to diverse geographic, climatic conditions and natural cultivated regions of potato in China, the study areas were grouped into eight geographic regions: QT, Qinghai and Tibet; NE, Northeast China, NWI, Northwest irrigation region; NWD, Northwest dryland region; NC, North-central China; MLYR, The middle and lower reaches of Yangtze River; SW, Southwest China; S, South China.

Lines 126−127: Change the following - (1) PFM, plastic film mulching; (2) SM, straw mulching; and (3) PFSM, combination of plastic film and straw mulching.

Authors’ response: We are grateful to the reviewer for this suggestion, which we have followed (Line: 140-142).

the mulching methods were subject to three main categories: (1) PFM, plastic film mulching; (2) SM, straw mulching; and (3) PFSM, combination of plastic film and straw mulching.

Line 127: Please provide the type straw, for example, is it rice? Also, provide the nutrient content of the straw

Authors’ response: We are grateful to the reviewer for this suggestion, we described the straw materials in detail in the previous sentence “The straw materials in the literature comprised rice, wheat and maize straw” (Line:143-144). But we didn't calculate the quantity of crop straw nutrient content because Straw is used only as mulch, not as organic fertilizer, most straw mulching treatments do not provide the nutrient content of the straw.

Lines 131-132: Add FP and RFP as illustrated as follows: (1) straw and/or plastic film mulch on FP, flat plots; (2) straw and/or plastic film mulch on RFP, ridge-furrow plots.

Authors’ response: We are grateful to the reviewer for this suggestion, which we have followed (Line: 146-148).

the tillage practices were subject to two main categories: (1) straw and/or plastic film mulch on FP, flat plots; (2) straw and/or plastic film mulch on RFP, ridge-furrow plots.

Lines 133−135: Should the section read as follows - nitrogen (N) fertilizers application rates were categorized as <100, 100–200, 200–300, and >300 kg N ha−1, phosphorus application was categorized as <43, 43–87, 87–130, and >130 kg P ha−1 and potassium (K) fertilizer rates were categorized as 0, 0–83, 83–166, and >166 kg K ha–1. I would use P and K instead of P2O5 and potash. I think it is better to use P and K to be consistent with using N. I also think the word synthetic is not required when referring to fertilizer. I have converted 100–300 kg P2O5 ha-1 to 43–130 kg P ha-1 and 100–200 kg K2O ha-1 to 83-166 kg K ha-1. Perhaps it would be good to provide a comment on N, P and K fertilizers rates used on potatoes in China in the Materials and Methods section. That is paper presents fertilizer rates used in experiments. It would be helpfully for the reader to know the fertilizer rates used by growers.

Authors’ response: Thank you for this observation, but we don't agree with this suggestion. Because in agronomy, the application rate of N fertilizer is stated in kg N ha-1, the application rate of P fertilizer is stated in kg P2O5 ha-1 and the application rate of K fertilizer is stated in kg K2O ha-1.

Line 137: What are the organic fertilizers and their associated nutrient contents?

Authors’ response: We are grateful to the reviewer for this suggestion. The organic fertilizer mentioned in the article is livestock manure, we explained the organic fertilizer in the previous sentence “Organic fertilizer (i.e., livestock manure)” (Line: 84). Because there are many kinds of organic fertilizer, and the nutrient content is not unique, so most of the literatures only reported the organic fertilizer application rate. According to the literature we collected, the organic fertilizer application rate was about 10−75 Mg ha−1 for potato production in China. We added this result to the results section (Line: 84).

Lines 139−141: The statement reads as if the P was applied as a basal treatment? Please re-write the statement.

Authors’ response: We are grateful to the reviewer for this suggestion, we re-write the statement. We deleted this sentence because it repeats the previous sentence.

In all figures: I think it would be better to remove the symbol from the error bars presented in the figures. Often the symbol is larger than the error bar.

Authors’ response: We are grateful to the reviewer for this suggestion. We narrowed down the symbol in all figures.

Line 182: N fertilizer use efficiency (NUE) is stated on line 73. Please delete nitrogen use efficiency and just use NUE in the rest of the paper.

Authors’ response: We are grateful to the reviewer for this suggestion, which we have followed.

Lines 182−187: The caption does not reflect the presentation in figures a, b and c. Perhaps the caption could be changed to the following. The response of change in potato yield and NUE to mulching compared to no mulching average for China (a) and for the 8 regions for potato yield (b) and NUE (c). (Abbreviations: NC, North-central China; QT, Qinghai and Tibet; NE, Northeast China; NWI, Northwest irrigation region; NWD, Northwest dryland region; MLYR, The middle and lower reaches of Yangtze River; SW, Southwest China; and S, South China).

Authors’ response: We are grateful to the reviewer for this suggestion, , which we have followed (Lines: 204-213).

Figure 3. The response of change in potato yield and NUE to mulching compared to no mulching average for China (a) and for the 8 regions for potato yield (b) and NUE (c). (Abbreviations: NC, North-central China; QT, Qinghai and Tibet; NE, Northeast China; NWI, Northwest irrigation region; NWD, Northwest dryland region; MLYR, The middle and lower reaches of Yangtze River; SW, Southwest China; and S, South China). Error bars represent 95% confidence intervals. The values for n represent the corresponding number of observations.

Lines 193−197: North China Plain region not stated in the regions in lines 118-122. Should it be North-central China?

Authors’ response: Thank you for this observation. We are so sorry for our carelessness. North China Plain region should be North-central China, this was corrected.

Lines 210−214: Caption needs correcting because references to figures e and f are not included. Please edit caption with reference to these figures.

Authors’ response: Thank you for this observation. We are so sorry for our carelessness, this was corrected (Lines: 236-240).

Figure 4. Response of change in potato yield (a, c, e) and NUE (b, d, f) to mulching compared to no mulching with different mulching and tillage practices. Error bars represent 95% confidence intervals. The values for n represent the corresponding number of observations. PFM, plastic film mulching; SM, straw mulching; PFSM, combination of plastic film and straw mulching; FP, flat plots; RFP, ridge-furrow plots.

Lines 279-284: Please present phosphorus rates as P instead as P2O5.

Authors’ response: Thank you for this observation, but we don't agree with this suggestion. Because in agronomy, the application rate of P fertilizer is stated in kg P2O5 ha-1.

Lines 290-295: Please present potassium rates as K instead as K2O.

Authors’ response: Thank you for this observation, but we don't agree with this suggestion. Because in agronomy, the application rate of K fertilizer is stated in kg K2O ha-1.

Lines 310−311. Need a statement on the timing of fertilizer applications in the Materials and Methods section for the different regions.

Authors’ response: We are grateful to the reviewer for this suggestion. We added information about fertilization in revised manuscript (Lines: 134-138).

A study detailedly evaluated the NUE of potato in China, the results showed that in NE and NC, in most cases, potato received eight topdressing; however, in NWI, NWD, MLYR, SW, and S, potato received less than three topdressing [33]. On average, the application rate of N fertilizer was 360 kg N ha−1 in China, for eight geographic regions (NE, NC, NWI, NWD, QT, MLYR, SW, and S), the application rate of N fertilizer was 228, 471, 330, 280, 300, 400, 300, and 390 kg N ha−1, respectively [33].

Yu, J.; Xiong, X.Y.; Gao, Y.L.; Wang, G.J.; Wang, W.X.; Lyu, H.P.; Fan, M. Comparative Analysis of Nitrogen Use Efficiency in Different Potato Production Areas of China. China Vegetables, 2019, 7, 43-50 (in Chinese).

Round 2

Reviewer 1 Report

1. Towards the comment - In the introduction line 43, the study introduces the importance of potato and describes the demand for the crop with a projection until 2020 with one study referencing it. A more long-term projection with more relevant references need to be included.

A link to a video has been referenced, but not really showing the importance or long-term demand of the crop. 

2. Correction to the grammar on lines 325, 452 is required

Author Response

1. Towards the comment - In the introduction line 43, the study introduces the importance of potato and describes the demand for the crop with a projection until 2020 with one study referencing it. A more long-term projection with more relevant references need to be included.

A link to a video has been referenced, but not really showing the importance or long-term demand of the crop.

Authors’ response: We are grateful to the reviewer for this suggestion, we revised the sentence to address this suggestion.

Potato (Solanum tuberosum L.) is one of the most important staple foods and the annual fresh yield has reached 365 million tons ranking the fourth staple food crop after maize (Zea mays L.), wheat (Triticum aestivum L.), and rice (Oryza sativa L.) [1, 2].

2. Correction to the grammar on lines 325, 452 is required.

Authors’ response: We are grateful to the reviewer for this suggestion. There is a contradiction between this sentence on lines 325 and the previous one, we deleted the sentence “A negative effect of mulching on yield was occurred when plant density was >85,000 plants ha–1.” (Lines 325). We also changed the sentence “high N, P, and K fertilization, when organic fertilizer was applied, did not improve increase yield and reduced NUE, in agreement with previous studies (Lines 452)”  to  “Under these conditions, high application rates of N, P, and K limited the effect of mulching on yield and NUE of potato, in agreement with previous studies [15, 56]”

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