Effect of Nitrogen Application on Root and Yield Traits of Chinese Spring Wheat (Triticum aestivum L.) under Drip Irrigation

Round 1

Reviewer 1 Report

 

Dear Prof. Dr. Editor of Agronomy,

 

I write you regarding Manuscript Number: agronomy-1929871 entitled " Effect of nitrogen application on root growth and yield of drip irrigated spring wheat in Xinjiang, China" which was submitted to Agronomy Journal.

In this manuscript, the authors studied the Effect of nitrogen application on root growth and yield of drip irrigated spring wheat in Xinjiang, China. This work was well done, and the methods of data collection were appropriate. The manuscript is suitable for publication in Agronomy Journal.

I have gone through this work. My decision is accepted with minor revisions for this work. The reason for that is as follows:

The manuscript deals with " Effect of nitrogen application on root growth and yield of drip irrigated spring wheat in Xinjiang, China.

First: Title: It should change to the following:

1)  Effect of nitrogen application on root and yield traits of Chinese spring wheat (Triticum aestivum L.) under drip irrigated 

Second Abstract, keywords and Introduction:

2) has some minor corrections as in the attached file.

Third: The objectives of the study

3) is not clear so try to rewrite in clear points as in the attached file.

Fourth: Materials and Methods

4) has some minor corrections as in the attached file.

Results and discussion

5)  has some minor corrections as in the attached file.

References

6) has some minor corrections as in the attached file.

Thank you for suggesting me as a reviewer for this paper.

with best regards

 

Comments for author File: Comments.pdf

Author Response

Dear Editor and Reviewers:

On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript. we appreciate you very much for your positive and constructive comments and suggestions on our manuscript entitled "Effect of nitrogen application on root growth and yield of drip irrigated spring wheat in Xinjiang, China" (ID: agronomy-1929871).

We have studied reviewers’ comments carefully and tried our best to revise our manuscript according to the comments.The following are the responses and revisions I have made in response to the reviewers' questions and suggestions on an item-by-item basis. Thanks again to the hard work of the editor and reviewer!

 

Response to the comments of Reviewer #1

 

Comment No.1: Title: It should change to the following Effect of nitrogen application on root and yield traits of Chinese spring wheat (Triticum aestivum L.) under drip irrigated. 

Response: Thanks to reviewer for suggestions, we have revised the title in the manuscript.

 

 

Comment No.2: Abstract, keywords and Introduction has some minor corrections as in the attached file.

Response: Thanks to reviewer for suggestions, we have made changes to the corresponding parts in the manuscript.

 

 

Comment No.3: The objectives of the study is not clear so try to rewrite in clear points as in the attached file.

Response: Thanks to reviewer for valuable comment, according to your suggestion, I will revise the research objectives as "According to the unique ecological environment of Xinjiang, this study selected two spring wheat varieties with different gluten types, through soil column cultivation, and studied the effects of different nitrogen changes on the root morphology and spatial distribution, root activity, changes in key enzyme activities of nitrogen metabolism, dry matter accumulation and yield of spring wheat under drip irrigation conditions, which provided scientific basis for nitrogen saving and high-yield cultivation of spring wheat under drip irrigation in Xinjiang." We have made corresponding modifications in the manuscript.

 

 

Comment No.4: Materials and Methods has some minor corrections as in the attached file.

Response: Thanks to reviewer for suggestions, we have made changes to the corresponding parts in the manuscript.

 

Comment No.5: Results and discussion has some minor corrections as in the attached file.

Response: Thanks to reviewer for suggestions, we have made changes to the corresponding parts in the manuscript.

 

 

Comment No.6: References has some minor corrections as in the attached file.

Response: Thanks to reviewer for suggestions, we have made changes to the corresponding parts in the manuscript.

Author Response File: Author Response.doc

Reviewer 2 Report

Abstract: Too detailed, the abstract should not cite single detailed results but allow an overview of the paper.

 Introduction:

The nitrogen uptake capability of wheat has not been treated. This missing part needs to be added. How should it be possible to discuss a an adjusted fertilisation if the uptake is not taken into account? Why fertilising much more than what the plants can take up?

 

Results

This paper contains by far too many graphs. There’s no need to show all detailed results. Apart some graphs, use tables to publish the relevant data. Creating an annex or publish data online could be another way. You showed that many parameters are strongly correlated. So there’s probably no need to publish the single results then.

 

Abreviations: You used abbreviations excessively, what makes the paper hard to read. Only introduce abbreviations for terms you use very frequently.

 

L79 explain the expression 275 kg*hm^-2 = 275 kg N per 100 m² = 27500 kg N/ha ??
This can’t be correct. Can you please clear this missunderstandig. Probably this has to be interpreted as 275 kg N/ha. (ha are in harmony with the SI-System!)

L 84 avoid the word “reasonable” N supply, this is not defined at all and very unclear. It’s difficult to characterize your incredibly high N-supplies as “reasonable”.

 

Table 1

EC/dS m-1 à do you mean EC [dS/m], put units in brackets, then it’s clear what you mean. The “/” often expresses a division “:”

 

L 194 Tube with diameter of 10 cm allows space for about 4.7 wheat plants (600 ears/m².) Why was the sowing densitiy the double of that usual seed density?

 

L 189 irrigation is normally expressed as mm of water.

 

L199 did you place 1 dripper above each tube or how did you handle the irrigation?

 

Table 2 N supply of 210 kg/ha is still very high…

 

L 277 How much higher was A1 than the other treatments, 17 %? Your list is not clear.

L 288 again a list of numbers which can’t be interpreted. Avoid to repeat detailed data in the text which should be presented in graphs or tables and focus on the relevant data.

 

L 294 Here you already start the discussion. These are not results

 

Table 3 for the application of over 200 kg N you had a low very low yield with 7000 kg grain/ha. Compare this with the literature. You can conclude that you had a big nitrogen surplus in all your treatments. Compared to your N0 treatment you only gained a supplementary yield of about 2000 kg /ha. What means that you generated only 10 kg of grain per 1 kg of N what is very low. So this shows, that you still had a big surplus of N in your experiment. This may be due to the artefact of your pipe experiment (sieved soil mineralised a lot of nitrogen!!). You find other literature too citing yields of 5000 kg grain/ha with no nitrogen fertilisation! Please discuss this accordingly.

 

Fig 15. This figure shows, that you unfortunately didn’t include a procedure with about 100 or 150 kg N/ha. All your treatments seem to heavily overfertilize the plants! As the treatments are in a small and very high range only this data can’t be clearly interpreted.

Indication how much nitrogen has been taken up by the plant and how much remained in the soil is missing. Didn’t you analyse this? If yes, then please present this data, otherwise discuss this based on other literature.

 

L 764 The differences between the treatments are not big, the generalisation is very risky and not databased.

L783 How can you speak about a good nitrogen use efficiency. Compared to the literature the nitrogen use efficiency was very, very low compared to N0.

 

L 788 Very strange to speak about low nitrogen supplies. Very probable a supply around 100 kg seems to be optimal for your situation, but as no data are available this can not been judged. Discuss this accordingly.

 

Author Response

Dear Editor and Reviewers:

On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript. we appreciate you very much for your positive and constructive comments and suggestions on our manuscript entitled "Effect of nitrogen application on root growth and yield of drip irrigated spring wheat in Xinjiang, China" (ID: agronomy-1929871).

We have studied reviewers’ comments carefully and tried our best to revise our manuscript according to the comments.The following are the responses and revisions I have made in response to the reviewers' questions and suggestions on an item-by-item basis. Thanks again to the hard work of the editor and reviewer!

 

Response to the comments of Reviewer #2

Comment No.1: Abstract: Too detailed, the abstract should not cite single detailed results but allow an overview of the paper.

Response: Thank you for your valuable comment. We have revised the abstract, and the revised abstract is “To clarify the regulatory effects of different N fertilizer treatments on root morphology, physiological characteristics, and assimilate accumulation of drip irrigated spring wheat under the northern border climate. We used strong wheat Xinchun 38 (cv. XC 38) and medium gluten wheat Xinchun 49 (cv. XC 49) as test materials in 2019 and 2020, and cultivated them in soil columns at Nck (300 kg/ha), A1 (240 kg/ha), A2 (210 kg/ha) and N0 (0 kg/ha). And studied the effects of N application on root morphological characteristics, key enzymes of N metabolism, antioxidant enzymes, dry matter accumulation distribution and yield of drip irrigated wheat. The results showed that the root morphological characteristics, key enzymes of nitrogen metabolism, antioxidant enzymes, shoot dry matter accumulation, spike dry matter, and yield all showed an increasing and then decreasing trend with increasing nitrogen application. Among them, A1 treatment showed the best root length density (RLD), root volume density (RVD), root mass density (RMD), nitrate reductase (NR), glutamine synthetase (GS), glutamate synthetase (GOGAT), glutamic-pyruvic transaminase (GPT), superoxide dismutase (SOD), peroxidase (POD), root activity, shoot dry matter accumulation, spike dry matter and yield, which were significantly higher than other treatments. The malondialdehyde (MDA) content decreased 3.36%~15.70% compared with other treatments. Correlation analysis showed that yield was positively correlated with RLD, RVD, RMD, GS, and GPT and negatively correlated with MDA. Nitrogen treatments and varietal intercropping had significant effects on RLD, root activity, NR, GS, GPT, POD, and yield. Therefore, moderate N reduction (240 kg/ha) under the drip irrigation pattern in Xinjiang can improve the morphological characteristics and physiological functions of wheat roots, promote the distribution and transport of dry matter to spike, and facilitate yield formation.”

 

Comment No.2: Introduction: The nitrogen uptake capability of wheat has not been treated. This missing part needs to be added. How should it be possible to discuss a an adjusted fertilisation if the uptake is not taken into account? Why fertilising much more than what the plants can take up?

Response: Thank you for your valuable comment. Our manuscript mainly studies the effect of nitrogen application rate on the morphological and physiological characteristics of root in the Xinjiang. The reason why the amount of fertilizer application far exceeds the plant absorption is that there is a concept of high yield and high fertilizer in Xinjiang's actual production, as well as soil fertility and environmental factors, the desertification of soil is so serious that it does not keep fertilizer and the loss is so serious that the utilization rate of nitrogen fertilizer is low. This is the problem that we need to solve next. The foreword is mainly written around our research content. According to your suggestions, we have added some content about the nitrogen absorption capacity of wheat in the introduction and discussion section.

The content added in the introduction is “From the perspective of wheat itself, developed and strong root system is the basic factor for nitrogen absorption and utilization of wheat. At present, the research on nitrogen absorption capacity is mostly carried out from the perspective of root system, and its morphological and physiological characteristics are closely related to canopy growth and yield formation.” 

The discussion is added as “ Nitrogen is the primary factor to promote wheat growth and yield formation, and nitrogen uptake is the primary factor to improve yield. Some studies have shown that three main directions after the application of nitrogen fertilizer: plant absorption, soil residue, and loss of multiple ways such as leaching, denitrification, ammonia volatilization. Our research team showed that the proportion of nitrogen fertilizer absorption, soil residue and loss in wheat maturity was 28.6%, 28.6% and 42.8%, respectively, but some studies believed that the three proportions were 49%, 30% and 21%, respectively. The research results were inconsistent, which may be related to the impact of many factors such as nitrogen application amount, yield level, soil fertility status and variety differences on nitrogen fertilizer utilization in production practice. Therefore, increasing nitrogen uptake of wheat can regulate the accumulation and transportation of assimilates, which is conducive to dry matter accumulation and yield formation” 

 

Comment No.3: This paper contains by far too many graphs. There’s no need to show all detailed results. Apart some graphs, use tables to publish the relevant data. Creating an annex or publish data online could be another way. You showed that many parameters are strongly correlated. So there’s probably no need to publish the single results then.

Response: It is really true as reviewer mentioned that we have many graphs in our manuscript. We modified the graphs of root morphology traits and antioxidant enzyme activities into tables and inserted them into corresponding positions.

 

Comment No.4: Abreviations: You used abbreviations excessively, what makes the paper hard to read. Only introduce abbreviations for terms you use very frequently.

Response: Thank you for your valuable comment, we think that abbreviations can reduce the problem of space. We marked them when they first appeared. According to your suggestion, we reserved common abbreviations, changed the uncommon abbreviations to full names, and changed the full names to RA: root activity, SDM: shoot dry matter, and RODM: reproductive organs dry matter. These three abbreviations have been modified in the manuscript.

 

Comment No.5: L79 explain the expression 275 kg*hm^-2 = 275 kg N per 100 m² = 27500 kg N/ha ?? This can’t be correct. Can you please clear this missunderstandig. Probably this has to be interpreted as 275 kg N/ha. (ha are in harmony with the SI-System!)

Response: We are sorry that we may have not expressed it clearly, we didn't use the unit in the system, which caused a misunderstanding. Ha and hm² have the same meaning, both are hectares.1 ha=1hm²=10000 m², so 275 kg hm^-2 = 275 kg N 10000 m² = 275 kg N/ha. In the paper, we have replaced all units with ha. 

 

Comment No.6: L84 avoid the word “reasonable” N supply, this is not defined at all and very unclear. It’s difficult to characterize your incredibly high N-supplies as “reasonable”.

Response: Thank the reviewer for the suggestions. We believe that under the high nitrogen level, the wheat related enzyme activity and yield did not reach the maximum. Within a certain threshold, with the decrease of nitrogen fertilizer, the yield will increase first and then decrease. We regard the corresponding nitrogen application amount when the yield reaches the maximum as a reasonable nitrogen application amount. This description may be misunderstood. In the manuscript, we modified it to "proper reduction of nitrogen application", which can further explain our description. Secondly, the nitrogen treatment we set is based on the amount of nitrogen fertilizer applied in the local spring wheat production in Xinjiang, China. In Xinjiang, many farmers still have the idea of high yield and high fertilizer. The nitrogen fertilizer application rate of spring wheat in the whole growth period is maintained at 300 kg/ha, or even more in some places. Therefore, we set the nitrogen application rate of 300 kg/ha as the control group. Many studies have also shown this. Here are two references to illustrate this problem.

 

Wan, W. L., Zhao, Y. H., Wang, Z. J., Li, L. L., Jing, J. G., Lv, Z. Y., Diao, M., Li, W. H., Jiang, G. Y., Wang, X., Jiang, D., (2022). Mitigation fluctuations of inter-row water use efficiency of spring wheat via narrowing row space in enlarged lateral space drip irrigation systems, Agricultural Water Management, 274, 107958. https://doi.org/10.1016/j.agwat.2022.107958

 

Chen, R., Cheng, W. H., Cui, J., Liao, J., Fan, H., Zheng, Z., Ma, F. Y., (2015). Lateral spacing in drip-irrigated wheat: The effects on soil moisture, yield, and water use efficiency, Field Crops Research, 179, 52-62. https://doi.org/10.1016/j.fcr.2015.03.021

 

Comment No.7: Table 1  EC/dS m^-1 à do you mean EC [dS/m], put units in brackets, then it’s clear what you mean. The “/” often expresses a division “:”

Response: We are very sorry for our negligence of mistakenly, we have revised this issue in the manuscript and other similar issues in the manuscript.

 

Comment No.8: L194 Tube with diameter of 10 cm allows space for about 4.7 wheat plants (600 ears/m2.) Why was the sowing densitiy the double of that usual seed density?

Response: We are sorry that we did not clearly describe the seeding amount. In order to ensure the emergence of seedlings, we sowed 10 seeds and seedlings were thinned to 5 at the trefoil stage. We have described the final number in detail in the manuscript.

 

Comment No.9: L189 irrigation is normally expressed as mm of water. 

Response: According to your suggestion, we convert m³ into mm, 6000 m³·hm^-2=600 mm

 

Comment No.10: L199 did you place 1 dripper above each tube or how did you handle the irrigation?

Response: Thank you very much for your questions on how to irrigate. We use drip irrigation, which is unique to Xinjiang, China. Before sowing, we dig a square pool with a depth of 60 cm, place the 60 cm long PVC pipe in the square pool orderly. The upper part of the PVC pipe is level with the ground. After filling with soil, a drip irrigation belt is laid on the upper part of the PVC (passing through the center) for irrigation. The fertilizer is dissolved in the fertilizer tank and applied with water. The amount of irrigation is controlled by the water meter.

 

Comment No.11: Table 2 N supply of 210 kg/ha is still very high…

Response: The nitrogen treatment we set is based on the amount of nitrogen fertilizer applied in the local spring wheat production in Xinjiang, China. In Xinjiang, many farmers still have the idea of high yield and high fertilizer. The nitrogen fertilizer application rate of spring wheat in the whole growth period is maintained at 300 kg/ha, or even more in some places. Therefore, we set the nitrogen application rate of 300 kg/ha as the control group. Many studies have also shown this. Here are two references to illustrate this problem.

 

Wan, W. L., Zhao, Y. H., Wang, Z. J., Li, L. L., Jing, J. G., Lv, Z. Y., Diao, M., Li, W. H., Jiang, G. Y., Wang, X., Jiang, D., (2022). Mitigation fluctuations of inter-row water use efficiency of spring wheat via narrowing row space in enlarged lateral space drip irrigation systems, Agricultural Water Management, 274, 107958. https://doi.org/10.1016/j.agwat.2022.107958

 

Chen, R., Cheng, W. H., Cui, J., Liao, J., Fan, H., Zheng, Z., Ma, F. Y., (2015). Lateral spacing in drip-irrigated wheat: The effects on soil moisture, yield, and water use efficiency, Field Crops Research, 179, 52-62. https://doi.org/10.1016/j.fcr.2015.03.021

 

Comment No.12: L277 How much higher was A1 than the other treatments, 17 %? Your list is not clear.

Response: We are sorry that we may have not expressed it clearly, “At the flowering stage, A1 treatment was significantly 17.44%~138.83%, 14.33%~139.15%, 15.09%~168.94% higher than other treatments.” The corresponding three groups of data in this sentence are RLD, RVD and RMD. We have listed these three percentages, which indicate how much higher A1 treatment is than other treatments. We will revise this sentence to make it more clear and detailed. The revised sentence is: At the flowering stage, RLD, RVD, and RMD at A1 were significantly 17.44%~138.83%, 14.33%~139.15%, 15.09%~168.94% higher than other treatments, respectively.

 

Comment No.13: L288 again a list of numbers which can’t be interpreted. Avoid to repeat detailed data in the text which should be presented in graphs or tables and focus on the relevant data.

Response: Thank the reviewer for the suggestions. The data presented here are calculated based on the detailed data, representing the reduction range of each indicator. According to your suggestions, we will delete the L288 data and try to reduce it in the manuscript.

 

Comment No.14: L294 Here you already start the discussion. These are not results.

Response: Thank you for your valuable comment, we have deleted the sentence you pointed out, and checked the other contents of the results, and no similar sentence will appear.

Comment No.15: Table 3 for the application of over 200 kg N you had a low very low yield with 7000 kg grain/ha. Compare this with the literature. You can conclude that you had a big nitrogen surplus in all your treatments. Compared to your N0 treatment you only gained a supplementary yield of about 2000 kg /ha. What means that you generated only 10 kg of grain per 1 kg of N what is very low. So this shows, that you still had a big surplus of N in your experiment. This may be due to the artefact of your pipe experiment (sieved soil mineralised a lot of nitrogen!!). You find other literature too citing yields of 5000 kg grain/ha with no nitrogen fertilisation! Please discuss this accordingly.

Response: Nitrogen mineralization refers to the process in which organic nitrogen in soil is transformed into inorganic nitrogen under the action of soil microorganisms. It is comprehensively affected by soil physical and chemical properties (such as organic matter content, nitrogen content, C/N, PH, water content), environmental climate factors (temperature, rainfall), soil microorganisms, field management measures (exogenous additives, nitrogen application, crop growth), etc. First, as you said, soil sieving will cause soil mineralization. Secondly, the loss of nitrogen in Xinjiang due to leaching, denitrification, ammonia volatilization, etc. is far more than the absorption of nitrogen by the plant itself. The research team has shown that about 40% of nitrogen fertilizer in Xinjiang is lost. This kind of problem is mainly due to the fact that the soil in Xinjiang is grey desert soil with poor water and fertilizer conservation. The nitrogen utilization efficiency is maintained at 30%~35% all the year round, far below the world level. However, this study does have limitations. Although it is similar to the planting and management method and the field, there are still differences between the pipe planting condition and the field environment. Later, we will conduct field planting according to the nitrogen application rate determined by the pipe planting test, which is suitable for Xinjiang, to further improve our research.

 

Comment No.16: Fig 15. This figure shows, that you unfortunately didn’t include a procedure with about 100 or 150 kg N/ha. All your treatments seem to heavily overfertilize the plants! As the treatments are in a small and very high range only this data can’t be clearly interpreted.

Response: The nitrogen treatment we set is determined according to the amount of nitrogen fertilizer applied in the local spring wheat production in Xinjiang, China. In Xinjiang, many farmers still have the idea of high yield and high fertilizer. The nitrogen fertilizer application rate of spring wheat in the whole growth period was kept at 300 kg/ha, even higher in some places. Therefore, we set the nitrogen application rate as 300 kg/ha as the control group. There is a large range of grey desert soil in Xinjiang, with low soil fertility and easy loss of nitrogen fertilizer, so the actual production of 100 or 150 kg N/ha is too low for Xinjiang, which is not conducive to wheat growth, so we did not set 100 or 150 kg N/ha treatment in the design of experimental treatment.

 

Wan, W. L., Zhao, Y. H., Wang, Z. J., Li, L. L., Jing, J. G., Lv, Z. Y., Diao, M., Li, W. H., Jiang, G. Y., Wang, X., Jiang, D., (2022). Mitigation fluctuations of inter-row water use efficiency of spring wheat via narrowing row space in enlarged lateral space drip irrigation systems, Agricultural Water Management, 274, 107958. https://doi.org/10.1016/j.agwat.2022.107958

 

Chen, R., Cheng, W. H., Cui, J., Liao, J., Fan, H., Zheng, Z., Ma, F. Y., (2015). Lateral spacing in drip-irrigated wheat: The effects on soil moisture, yield, and water use efficiency, Field Crops Research, 179, 52-62. https://doi.org/10.1016/j.fcr.2015.03.021

 

Comment No.17: Indication how much nitrogen has been taken up by the plant and how much remained in the soil is missing. Didn’t you analyse this? If yes, then please present this data, otherwise discuss this based on other literature.

Response: Thank you for your question, because in this manuscript, we mainly carry out research based on the Xinjiang environment to analyze the effects of root morphology and physiological characteristics under different nitrogen conditions. In this manuscript, we do not have any work related to nitrogen absorption by plants and the lack of nitrogen in soil. However, we have only conducted a one-year experiment on how much nitrogen plants absorb and how much residue remains in the soil, which is not representative. We plan to take this work as a long-term research content. Our preliminary research is that there are three main directions after the application of nitrogen fertilizer: plant absorption, soil residue, and loss through leaching, denitrification, ammonia volatilization and other ways, and nitrogen loss accounts for a large proportion. However, according to previous studies, the nitrogen utilization efficiency in Xinjiang is only 30%~35%, which is extremely low. Part of the reason is that the planting land in Xinjiang is grey desert soil, which has low soil fertility, is very easy to lose nitrogen fertilizer, and the soil salinization is relatively serious. In addition, Xinjiang is a semi-arid area, and the highest temperature during wheat growth can reach about 40 ℃, so the fertilizer is easy to volatilize. Therefore, in actual production, the amount of nitrogen fertilizer is often increased to about 300 kg/ha, even higher in some regions, resulting in the nitrogen fertilizer utilization efficiency being far lower than the international level. On the other hand, the concept of high yield and high fertilizer in the planting process is serious, and the reasonable nitrogen application amount cannot be determined according to the nitrogen demand of plants and soil nitrogen content. Therefore, our next work plan is to study the law of fertilizer demand of drip irrigation spring wheat under the climatic conditions and ecological environment of Xinjiang.

According to the literature, the proportion of nitrogen absorption, soil residue and loss during wheat maturity was 37.5%, 28.6% and 33.9% respectively. When the amount of nitrogen applied during the whole growth period of wheat is 150~300kg/ha, the contribution rate of nitrogen fertilizer to the nitrogen absorption of wheat is about 35%, the recovery rate of nitrogen fertilizer is 39.3%, the residual rate of soil decreases to 30.9%, and the loss rate of nitrogen fertilizer increases to 29.9%. The overall trend of nitrogen fertilizer is recovery rate>residual rate>loss rate. Some studies also believe that nitrogen fertilizer absorption The proportion of soil residue and loss is 49%, 30% and 21% respectively, which is inconsistent with the research results. This may be related to the fact that nitrogen fertilizer utilization in production is affected by many factors, such as nitrogen application amount, nitrogen application period, yield level, soil fertility status, variety difference, etc.

 

Shi, Z. L., Jing, Q., Cai, J., Jiang, D., Cao, W. X., Dai, T. B., (2012). The fates of ¹⁵N fertilizer in relation to root distributions of winter wheat under different N splits. European Journal of Agronomy, 40, 86-93. https://doi.org/10.1016/j.eja.2012.01.006

 

LI, X. X., Shi, Z. L., Wang, J. C., Wang, F., Xu, Z. Y., Jiang, R. F., (2020). Characteristics of uptake，residual and loss of nitrogen fertilizer in winter wheat after rice stubble. Chinese Journal of Applied Ecology, 31(11), 3691-3699. https://doi.org/10.13287/j.1001-9332.202011.021(in Chinese with English abstract)

 

Comment No.18: L764 The differences between the treatments are not big, the generalisation is very risky and not data based.

Response: Thank you for your valuable comment. According to L764 in the manuscript, when the amount of nitrogen application was 240 kg/ha, the shoot dry matter and the spike dry matter  reached the maximum. According to the data in Table 3 and the significance analysis, the difference between different treatments was significant at the 0.05 level. Because the nitrogen fertilizer utilization efficiency in Xinjiang was extremely low, reducing the amount of nitrogen application was a considerable way without reducing the yield.

 

Comment No.19: L783 How can you speak about a good nitrogen use efficiency. Compared to the literature the nitrogen use efficiency was very, very low compared to N0. 

Response: We are sorry that we may have not expressed it clearly. Because the nitrogen fertilizer utilization efficiency in Xinjiang is generally very low, about 30%~35%, far below the world level. Under this premise, what we want to show in the manuscript L783 is the difference between the two varieties in nitrogen fertilizer utilization efficiency. Under the same nitrogen fertilizer conditions, XC 38 has relatively high nitrogen fertilizer utilization efficiency, so the "good nitrogen use efficiency" described here refers to a relative value in Xinjiang, although this value is far below the world level, However, our description in the manuscript is based on the "good nitrogen nitrogen use efficiency" under a specific environment.

 

Gu, L. M., Liu, T. N., Wang, J. F., Liu, P., Dong, S. T., Zhao, B. Q., So, H. B., Zhang, J. W., Zhao, B., Li, J., (2016). Lysimeter study of nitrogen losses and nitrogen use efficiency of Northern Chinese wheat. Field Crops Research, 188, 82-95. https://doi.org/10.1016/j.fcr.2015.10.014

 

Zhang, F. F., Gao, S., Zhao, Y. Y., Zhao, X. L., Liu, X. M.,Xiao, K., (2015). Growth traits and nitrogen assimilation-associated physiological parameters of wheat (Triticum aestivum L.) under low and high N conditions. Journal of Integrative Agriculture, 14(7), 1295-1308. https://doi.org/10.1016/S2095-3119(14)60957-6

 

Comment No.20: L788 Very strange to speak about low nitrogen supplies. Very probable a supply around 100 kg seems to be optimal for your situation, but as no data are available this can not been judged. Discuss this accordingly.

Response: Thank you very much for your question, which is similar to comment 19. The low nitrogen supply I mentioned here is also a relative value. In some fertile soil areas in China, the amount of nitrogen applied to wheat is about 120 kg/ha, but there are two reasons for the high amount of fertilizer applied in Xinjiang. The first is the soil problem. The soil fertility is low, and salinization is serious and easy to lose. The second is the problem of planting concept. It is believed that the poor growth of wheat is due to insufficient fertilizer application. Therefore, many policies on nitrogen fertilizer application have been issued in Xinjiang, In recent years, the goal is "zero growth of fertilizer". So the nitrogen fertilizer treatment we set here is based on the average level of nitrogen fertilizer application in actual production of 300kg/ha as the control, and the nitrogen application amount of 240 kg/ha is relative to the control, which we call "low nitrogen treatment". In the actual wheat planting in Xinjiang, 240 kg/ha is indeed a relatively low nitrogen application amount. In the following documents, the field management also mentioned the relevant content of nitrogen fertilizer application amount during the whole growth period of wheat in Xinjiang.

 

Wan, W. L., Zhao, Y. H., Wang, Z. J., Li, L. L., Jing, J. G., Lv, Z. Y., Diao, M., Li, W. H., Jiang, G. Y., Wang, X., Jiang, D., (2022). Mitigation fluctuations of inter-row water use efficiency of spring wheat via narrowing row space in enlarged lateral space drip irrigation systems, Agricultural Water Management, 274, 107958. https://doi.org/10.1016/j.agwat.2022.107958

 

Chen, R., Cheng, W. H., Cui, J., Liao, J., Fan, H., Zheng, Z., Ma, F. Y., (2015). Lateral spacing in drip-irrigated wheat: The effects on soil moisture, yield, and water use efficiency, Field Crops Research, 179, 52-62. https://doi.org/10.1016/j.fcr.2015.03.021

 

Wan, W. L., Li, L. L., Jing, J. G., Diao, M., Lv, Z. Y., Li, W. H., Wang, J. L., Li, Z. F., Wang, X., Jiang, D., (2022). Narrowing row space improves productivity and profit of enlarged lateral space drip irrigated spring wheat system in Xinjiang, China. Field Crops Research, 280, 108474. https://doi.org/10.1016/j.fcr.2022.108474

 

 

Author Response File: Author Response.doc

Reviewer 3 Report

Dear Authors,

thank you for the opportunity to meet the manuscript entitled: "Effect of nitrogen application on root growth and yield of drip irrigated spring wheat in Xinjiang, China".

Research on the effect of nitrogen on plants is extensive, which from the point of view of novelty has a reduced effect on the quality of the manuscript. Therefore, I recommend the authors to change the title of the manuscript, while they should emphasize research on the effect of nitrogen on the activity of antioxidant and root nitrogen metabolism enzymes.

I have several comments regarding the preparation of the manuscript:

The text often contains excessively long sentences (e.g. L13-22), which impairs clarity and readability. I therefore recommend a formal and linguistic adjustment.

L23 Given that there are many different enzymes involved in the wheat growth process, I recommend that the authors specify which enzymes they consider to be key. Resp. on the basis of which they chose this terminology.

L208 I recommend using phase names based on a specific scale. It is not clear from this when exactly the sampling was done. In order to compare with other works, it is crucial to accurately determine the stages of collection.

L239 In my opinion, the RA parameter does not belong in this list. I recommend listing separately.

L301 I think this shows the overall effect of the factor at the selected level according to the analysis of variance. In addition, there is no sign of significance of differences between treatments based on the Duncan test. Please check and correct throughout the chapter.

L479 MM lacks information on determination the parameters presented in this chapter. Please add.

L524 Check the description on the Y axis in Figure 14.

Author Response

Dear Editor and Reviewers:

On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript. we appreciate you very much for your positive and constructive comments and suggestions on our manuscript entitled "Effect of nitrogen application on root growth and yield of drip irrigated spring wheat in Xinjiang, China" (ID: agronomy-1929871).

We have studied reviewers’ comments carefully and tried our best to revise our manuscript according to the comments.The following are the responses and revisions I have made in response to the reviewers' questions and suggestions on an item-by-item basis. Thanks again to the hard work of the editor and reviewer!

Response to the comments of Reviewer #3

Comment No.1: The text often contains excessively long sentences (e.g. L13-22), which impairs clarity and readability. I therefore recommend a formal and linguistic adjustment.

Response: Thank you very much for your suggestions. We have carefully revised and read the content of the manuscript, and let the relative professionals to revise it.

 

Comment No.2: L23 Given that there are many different enzymes involved in the wheat growth process, I recommend that the authors specify which enzymes they consider to be key. Resp. on the basis of which they chose this terminology.

Response: Thank you very much for your suggestions on our manuscript. We have supplemented the key enzymes in the nitrogen metabolism process in the manuscript according to your suggestions, but due to the length of the abstract, we have added this content in the introduction. As you said, there are many enzymes involved in the growth process of wheat. We mainly study the key enzymes in the nitrogen metabolism process. The nitrogen absorbed by crops is metabolized to synthesize all the proteins, nucleic acids and other nitrogen compounds needed in the body through a series of metabolism. NR, GS, GOGAT and GPT are the main enzymes involved in this metabolism process and play an important role in nitrogen metabolism. Therefore, we call them NR, GS, GOGAT GPT is a key enzyme for nitrogen metabolism, and Hu et al. (2016) and Ma et al. (2019) have the same terminology.

 

Hu, W., Zhao, W. Q., Yang, J. S., Oosterhuis, D. M., Loka, D. A., & Zhou, Z. G., (2016). Relationship between potassium fertilization and nitrogen metabolism in the leaf subtending the cotton ( Gossypium hirsutum L.) boll during the boll development stage. Plant Physiology and Biochemistry, 101, 113-123. https://doi.org/10.1016/j.plaphy.2016.01.019

 

Ma, C., Ban, T. T., Yu, H. J., Li, Q., Li, X. H., Jiang, W. J., Xie, J. M., (2019). Urea addition promotes the metabolism and utilization of nitrogen in cucumber. Agronomy 9, 262. https://doi.org/10.3390/agronomy9050262

 

Comment No.3: L208 I recommend using phase names based on a specific scale. It is not clear from this when exactly the sampling was done. In order to compare with other works, it is crucial to accurately determine the stages of collection.

Response: Thank you very much for the suggestions of the evaluation experts. When we judge the growth period, 50% of spring wheat has five leaves and a core, which is the jointing stage. 50% of the flag leaves of stems and tillers have all drawn out the leaf sheaths, which means that the wheat growth process enters the booting stage. 50% of the plants blossom, which is the flowering stage. About 10 days after flowering enter the milk ripening stage. Due to climate difference in two years and other reasons, the time of occurrence in the same period in two years is different. The difference is 3-5 days based on the number of days after sowing. Therefore, in the part of materials and methods, we have supplemented the sampling time in each period of two years, and the specific contents are as follows: The jointing stage (May 12, 2019 and May 6, 2020), booting stage (May 29, 2019 and 23, 2020), flowering stage (June 9, 2019 and June 2, 2020), milk ripening stage (June 21, 2019 and June 18, 2020).

 

Comment No.4: L239 In my opinion, the RA parameter does not belong in this list. I recommend listing separately.

Response: Thank you very much for pointing out our mistakes. We changed the description to the physiological traits of the root in the manuscript, which includes RA.

 

Comment No.5: L301 I think this shows the overall effect of the factor at the selected level according to the analysis of variance. In addition, there is no sign of significance of differences between treatments based on the Duncan test. Please check and correct throughout the chapter. 

Response: Thank the reviewers for for pointing out the problems in the data analysis. I have revised all the figures in the manuscript according to your suggestions. In the figure, different letters indicate the differences between different treatments in the same soil layer (at the 0.05 level). The two varieties are marked separately in the figure. The small letter can indicate whether there are differences between nitrogen treatments, rather than the impact of nitrogen fertilizer on wheat at a general level.

 

Comment No.6: L479 MM lacks information on determination the parameters presented in this chapter. Please add.

Response: Thank the reviewers for pointing out my mistakes. The title of section 3.3 on L479 is changed to Dry matter and yield. The specific description is shown in Table 5 and Figure 6. The determination methods of dry matter and yield are also supplemented in detail in the materials and methods section.

 

Comment No.7: L524 Check the description on the Y axis in Figure 14.

Response: Thank you very much for your reminder. What we want to express in the figure is the proportion of the spike biomass occupied shoot biomass, we may be wrong in our statement, and have made some modifications in the manuscript. Modified as spike mass fraction (spike mass fraction=spike biomass / shoot biomass).

 

 

Author Response File: Author Response.doc