The Influence of Winter Irrigation Amount on the Characteristics of Water and Salt Distribution and WUE in Different Saline-Alkali Farmlands in Northwest China

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes/Can be improved/Must be improved/Not applicable

Are all the cited references relevant to the research?

Yes/Can be improved/Must be improved/Not applicable

Is the research design appropriate?

Yes/Can be improved/Must be improved/Not applicable

Are the methods adequately described?

Yes/Can be improved/Must be improved/Not applicable

Are the results clearly presented?

Yes/Can be improved/Must be improved/Not applicable

Are the conclusions supported by the results?

Yes/Can be improved/Must be improved/Not applicable

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1:

Line 8: The first sentence lacks a determiner, “…alleviate soil salinization in Northwest China.”

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have modified the sentence. In line 8-11. “Winter irrigation is widely carried out to alleviate soil salinization in Northwest China.”

Comments 2: Line 54-55: The meaning of this sentence is difficult to get.

Response 2: We agree with this suggestion and have modified the sentence. In line 53-54.“Farmland water consumption has not decreased significantly due to the large amount of water consumption in winter”

Comments 3: In section 2.1 (Experimental site), please provide a brief description of Figure 1. In Figure 1, Highest and Lowest temperature should be “Maximum and minimum temperature”ET0 should be “ET₀”.

Response 3: Thank you for pointing this out. We have modified the statement in Figure 1.

Comments 4: In section 2.2 (Experimental design), the winter irrigation time 2018.11.11 and 2019.11.17 should be corrected by 11 Nov 2018 and 17 Nov 2019.

Response 4: Thank you for pointing this out. We have modified the date. In line 92-93. 

Comments 5: In section 2.3.1 (Soil sample and measurement), the description of the excavation date and depth is complex, it is recommended to simplify it.

Response 5: We agree with this suggestion and have modified the sentence in line 105-109. “Soil samples were taken in each plot with an auger (5 cm in diameter) before winter irrigation, after winter irrigation, freezing stage, initial thawing stage, and late thawing stage, respectively. Three sets of repeats were made for sampling point of different treatments and corresponding marks were made, and the average value was taken as the test result. For each treatment, 7 soil samples were taken within the depth of 0-100 cm (i.e., 0-5, 5-10, 10-20, 20-40, 40-60, 60-80 and 80-100 cm).”

Comments 6: In section 2.3.3 Please show what iWUE and IWUE stand for respectively.

Response 6: We agree with this suggestion and have add it. In line 144-145, iWUE is water use efficiency of cotton during the growth period, kg/m³; IWUE is water use efficiency of cotton considering winter irrigation and growth period, kg/m³.

Comments 7: The part of “Result” needs to be simplified to increase readability.

Response 7: Thank you for pointing this out. We agree with this comment and have simplified the result. In line 410-421

Comments 8: In section 3.1 (Soil moisture distribution characteristics during the freeze-thaw period), ‘the ET0 was the lowest’, the specific value of the ET0 should be explained.

Response 8: We agree with this suggestion and have add it. In line 165. “the ET0 was the lowest with the value of 0.73 mm”

Comments 9: In section 3.2 (Soil salinity distribution characteristics during the freeze-thaw period), replace ‘0.033 g/(cm²·d), 0.060 g/(cm²·d), 0.038 g/(cm²·d), -0.001 g/(cm²·d) and -0.023 g/(cm²·d)’ with ‘0.033, 0.060, 0.038, -0.001 and -0.023 g/(cm²·d)’. Just keep the unit of the last digit, please check the full text as required.

Response 9: Thank you for pointing this out. We agree with this comment and have checked the full text and improved it.

Comments 10: In Figure 7, the horizontal axis should correspond to the irrigation quota, rather than using the letters.

Response 10: Thank you for your suggestion. However ,we think that the letters are more succinctly represented on the horizontal axis, and the meaning of letters is clearly explained in line 265-268. So, We will continue to retain the letter representation of horizontal coordinates.

Comments 11: The table 2 needs to add significance analysis.

Response 11: We agree with this suggestion and have add significance analysis in table 2.

Comments 12: In Table 5 “kg/hm²·mm” should be “kg/m³”

Response 12: We agree with this suggestion and have modified the units. In line 203.

Comments 13: In figure 6, under different winter irrigation treatments, the soil salt flux didn’t change significantly from November to February of the following year, but the value in March and April was significantly changed, the further explanation is needed for its causes.

Response 13: We agree with this suggestion and had explain the reason. In line 356-362, “What’s more, during the freezing period, we observed that the soil salt flux in 0-100 cm profile was about 0 g/(cm²·d) for different irrigation treatments. It is because the decrease of soil temperature, leading to the decrease of the solubility of water to salt, as well as the decrease of the carrying capacity of water to salt. However, soil salinity significantly increased at the late thawing stage, which is due to the increase in temperature and evaporation intensity in March and April, some of the soil water recovers the dissolving capacity of water to salt, and can carry some salt to the upper part, which make the soil salt content slightly increased. As a result, salt return occurs in all treatments in spring.”

Comments 14:  In Figure 6C, the date of the first picture was wrong, replace ‘2019/11/25 -2019/02/10’ with ‘2019/11/25 -2020/02/10’.

Response 14: We agree with this suggestion and have modified the date. In Figure 6C.

Response to Reviewer 2 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes/Can be improved/Must be improved/Not applicable

Are all the cited references relevant to the research?

Yes/Can be improved/Must be improved/Not applicable

Is the research design appropriate?

Yes/Can be improved/Must be improved/Not applicable

Are the methods adequately described?

Yes/Can be improved/Must be improved/Not applicable

Are the results clearly presented?

Yes/Can be improved/Must be improved/Not applicable

Are the conclusions supported by the results?

Yes/Can be improved/Must be improved/Not applicable

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: WUE: water use efficiency (WUE), please note it at the first place in the manuscript.

Response 1: We agree with this suggestion and have modified it. In line 10. 

Comments 2: Many places in the text are missing spaces, such as “0-20cm, 0-100cm” in page 7, as well as the word and symbol”()”, please check the full text as required.

Response 2: Thank you for pointing this out. We agree with this comment and have checked the full text and improved it.

Comments 3: The basis for setting the winter irrigation amount to the five levels (0 mm, 150 mm, 225 mm, 300 mm, 375 mm) should be explained.

Response 3: Thank you for pointing this out. We have supplement the content. In line 90-91. “According to the irrigation water requirements of local farmland during the winter irrigation period[24] ”

Comments 4: The level of crop yield is largely related to management during the growth period, and the article may consider reducing the section 3.4 (Cotton growth indexes and yield).

Response 4: Thank you for pointing this out. We politely disagree. The technology of mulched drip irrigation has the characteristics of high irrigation frequency and shallow wetting depth, which limits the leaching depth of soil salt. Winter irrigation can alleviate soil salinization and is a prerequisite for high yield of cotton fields in Xinjiang. Reasonable amount of winter irrigation plays a positive role in improving the seedling rate and yield of cotton, which is a very important link in cotton field management. Of course, the management measures during the growth period are also very important, and the management measures during the growth period were consistent in the course of this research. Therefore, we consider section 3.4 to be an essential part of this article. 

Comments 5: As a control treatment, W1 may not take into account changes in water content. It can be observed that only the soil moisture contour lines treated with W1 are horizontally distributed, while the others treated with winter irrigation are vertically distributed. In addition, in the coldest season, the soil moisture content is the highest. Please further explain the reason for this phenomenon.

Response 5: We agree with this suggestion and had explain the reason. In line 352-355.“In winter irrigation treatments, the vertical distribution of soil moisture isopleth under freeze-thaw conditions is due to the decrease of surface evaporation capacity and soil matric suction, turning the temperature potential and gravity potential into be the dominant driving force of water movement. ”

Comments 6: Page 4, Figure 2: replace ‘field’ with ‘Field’.

Response 6: We agree with this suggestion and have modified the word. In line 97.

Comments 7: Page 6, section 3.1: Soil moisture distribution.

Response 7: We agree with this suggestion and have modified the sentence. In line 149.

Comments 8: Page 9,section 3.2: Soil salinity distribution.

Response 8: We agree with this suggestion and have modified the sentence. In line 203.

Response to Reviewer 3 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes/Can be improved/Must be improved/Not applicable

Are all the cited references relevant to the research?

Yes/Can be improved/Must be improved/Not applicable

Is the research design appropriate?

Yes/Can be improved/Must be improved/Not applicable

Are the methods adequately described?

Yes/Can be improved/Must be improved/Not applicable

Are the results clearly presented?

Yes/Can be improved/Must be improved/Not applicable

Are the conclusions supported by the results?

Yes/Can be improved/Must be improved/Not applicable

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Although some interesting results have been presented, justifications for choosing cotton as a test crop and for determining the aforementioned indices in the Introduction section were missing.

Response 1: We agree with this suggestion and the supplementary explanations have been provided. In line 49-50, “Cotton is the pillar industry of Xinjiang agriculture, and it is also the largest production base of high-quality commercial cotton in China and the most important in the world”.

Comments 2: The Material and Methods section is not coherent enough, as some aspects of the methodology are found later in the Results section, and also it lacks relevant details and references to ensure reproducibility of the results.

Response 2: We agree with this suggestion and have condensed this part.

Comments 3: Lines 14-15: Consider replacing “layer depth of the maximum moisture content in soil” with “wetting depth” if that is what you mean?

Response 3: Thank you for your suggestion, but our understanding differs from yours. In order to facilitate understanding, the relevant statements are simplified in full text, replace ”layer depth of the maximum moisture content in soil” with ”the maximum soil moisture content layer”.

Comments 4: What is the pH range of the alkaline soil?

Response 4: Thank you for pointing this out. We have supplement the PH of soil. In Table 1. 

Comments 5: On what basis were the irrigation amount determined? Any reference

Response 5: Thank you for pointing this out. We have supplement the content. In line 90-91, “According to the irrigation water requirements of local farmland during the winter irrigation period[24] ”

Comments 6: It was stated that “In growth period, irrigation amount was 475 mm for all treatments, and the irrigation schedule and fertilization method were the same for all treatments”.

a) Does it mean that the treatments deployed in 2018-2019 were not repeated in 2019-2020?

b) Could you clarify the following terminologies used in the manuscript; “winter irrigation amount” and “irrigation amount in growth period”?

Response 6:

a) Thank you for pointing this out. In this research, the treatments deployed in 2018-2019 were repeated in 2019-2020, We have refined the statement. In line 100-102, “For all treatments, irrigation schedule and fertilization method control into the same both in 2018-2019 and 2019-2020, with 475 mm irrigation amount during the growth period.”

b) Winter irrigation measures are carried out after the harvest of crops. The main purpose of the implementation of this technology is to control soil salinity and provide a certain amount of soil moisture for the next year's crop planting. In this stage, crops are not planted in the farmland. However, he irrigation amount in growth period is the total amount of irrigation during the period from planting to harvesting.

Comments 7: What is the justification for choosing the ‘Xinluzhong 66’ cotton cultivar?

Response 7: Thank you for pointing this out. We have supplement the reason of choose the seed of cotton. In line 99-100, “The cotton cultivar "Xinluzhong 66" was commomly planted in the local area with a planting density of 2.41×10⁵ plants/hm²”.

Comments 8: Lines 136-140: Consider replacing “water user efficiency” with “crop water productivity” to avoid confusion, as some publications use the former interchangeably with “field application efficiency”. You may refer to the following article;

Kilemo, D.B. (2022) The Review of Water Use Efficiency and Water Productivity Metrics and Their Role in Sustainable Water Resources Management. Open Access Library Journal, 9, 1-21. https://doi.org/10.4236/oalib.1107075  

Response 8: Thank you for your valuable advice. In Xinjiang, winter irrigation is an essential farmland operation and was usually ignored in calculating water use efficiency. However, this part of water also plays a great role in arid and water-scarce areas. In this article, iWUE represent water use efficiency of cotton during the growth period, IWUE represent water use efficiency of cotton considering winter irrigation and growth period. Through this expression method, the comparison between iWUE and IWUE can be more intuitive.

4. Response to Comments on the Quality of English Language

Point 1:: The sentence in lines 8-10 ("Despite the fact that in recent years the effects of irrigation amount and irrigation schedule on soil water-salt distribution and WUE during crop growing period have been extensively researched") is incomplete

Response 1: Thank you for pointing this out. We have revised the statement, In line 8-11, “In recent years, the effects of irrigation amount and irrigation schedule on soil water and salt distribution and water use efficiency (WUE) during crop growth period have been extensively studied, but the effects of winter irrigation on water use efficiency have been generally ignored”

Point 2: The sentence in Lines 156-159 (From December to February next year, the coldest period in winter, the ET0 was the lowest (Figure 1), and the soil moisture content showed the highest value in 0-100cm profile, the layer depth of the maximum moisture content in soil became shallower with the increase of winter irrigation amount and the salinity of soil") is convoluted.

Response 2: Thank you for pointing this out. We have revised the statement, In line 160-162, “From December to February next year, the coldest period in winter, the ET0 was the lowest with the value of 0.73 mm (Figure 1). The the maximum soil moisture content layer became shallower with the increase of winter irrigation amount”

Point 3: What exactly is meant in line 330 (After winter irrigation, soil water transforms between solid and liquid under the influence of temperature)?

Response 3: Thank you for pointing this out. We have revised the statement, In line 338, “After winter irrigation, soil moisture changes from liquid to solid under the influence of temperature”.

Point 4: Again, what is meant lines 331-332: (The evaporation intensity of surface soil decreases and condensation water occurs, which decreases the water loss amount of the surface soil)?

Response 4: Thank you for pointing this out. We have revised the statement, In line 338-340, “At low temperature, evaporation intensity decreases and surface soil condenses, thus reducing the water loss of surface soil.”

Point 5: Line 335: what is the meaning of "layer depth of the maximum soil moisture content"?

Response 5: The same problem occurred in comment 3, and the ”layer depth of the maximum moisture content in soil”means “the maximum soil moisture content layer”.