Influence of Irrigation on Vertical Migration of Soil Organic Carbon in Arid Area of Inland River

Round 1

Reviewer 1 Report

Dear Authors,

You have presented a good study regarding migration of SOC under arid conditions. I have few qestions and suggestions to you.

1. You should mention excusively about the site , whether it is cultivated or not?

2. You have mentioned in your results that irrigation overall increases the total SOC content in the profile of 0-100 cm soil. whether you have done statistical analysis? if yes, you should put a seperate table for it and discuss the possible reasons explaining this particular results.

3. there are few typo errors which needs to addressed.

Comments for author File: Comments.pdf

Quality of english language is satisfactory.

Author Response

Response to Reviewer #1

You have presented a good study regarding migration of SOC under arid conditions. I have few questions and suggestions to you.

Thank you very much for reviewing our article. Your suggestions are very important for improving the quality of our article. We have explained the key issues you mentioned. The detailed explanations are as follows, and we hope to get your approval.

1. You should mention excusively about the site , whether it is cultivated or not?

According to your suggestion, we have explained the key issue you mentioned. The detailed explanation is as follows. Our study area is cultivated land, located in Beidan Village, Minqin Oasis.

2. You have mentioned in your results that irrigation overall increases the total SOC content in the profile of 0-100 cm soil. whether you have done statistical analysis? if yes, you should put a seperate table for it and discuss the possible reasons explaining this particular results.

According to your suggestion, we have explained the key issue you mentioned. The detailed explanation is as follows.

We have conducted detailed statistical analysis during the research process, and irrigation has generally increased the SOC content in 0-100 cm soil. The increase amount of SOC content under six different irrigation conditions was 1.98g, 1.58g, 1.86g, 1.46g, 0.90g and 0.15g, respectively. In Fig. 2, we have shown the change of SOC content in 0-100 cm soil after irrigation.

The reasons for the increase in soil SOC content caused by irrigation have been explained Discussion 5.1. The surface soil is greatly influenced by human factors, the cultivated measures make the surface soil relatively loose to a certain extent, enhance the permeability of soil, and facilitate the downward migration of organic carbon. However, with the deepening of the soil layer, the soil microbial community is gradually single, which is not conducive to the decomposition of soil organic matter . Moreover, the soil below the surface layer is less affected by management measures, and the organic carbon in the deep soil is gradually held by mineral clay to form carbon with complex structure, so the carbon storage capacity is strengthened and organic carbon is difficult to leach. At the same time, cultivating will destroy the continuity of soil pores in the cultivated layer and between the cultivated layer and the lower layer, and produce a compact layer at the bottom of the cultivated layer, which is beneficial to the interception of organic carbon. With the deepening of soil layer, the hydrodynamic force gradually decreases, and the migration ability of organic carbon also gradually weakens, which leads to the accumulation of organic carbon.

3. There are few typo errors which needs to addressed.

According to your suggestion, we have explained the key issue you mentioned. The detailed explanation is as follows.

• Irrigation increased the average SOC content.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows. We have changed ＂Irrigation increased the average SOC content＂ to ＂Irrigation increased the average 0-100 cm SOC content＂.

• It is estimated that about 7g•m^-2a^-1C in terrestrial ecosystem migrates with precipitation and irrigation per year. Is it degree celcius？

According to your suggestion, we checked the unit and changed ＂7g•m^-2•a^-1C＂ to ＂7g•m^-2•a^-1＂.

• Comparing the SOC content of soil before and after six irrigation events, it was found that irrigation increased the average SOC content of 0-100cm soil layer in the sample plot (Fig.2).You did not discussed this result properly in the discussion.

According to your suggestion, we have explained the key issue you mentioned. The detailed explanation is as follows.

The reasons for the increase in soil SOC content caused by irrigation have been explained Discussion 5.1. The surface soil is greatly influenced by human factors, the cultivated measures make the surface soil relatively loose to a certain extent, enhance the permeability of soil, and facilitate the downward migration of organic carbon. However, with the deepening of the soil layer, the soil microbial community is gradually single, which is not conducive to the decomposition of soil organic matter . Moreover, the soil below the surface layer is less affected by management measures, and the organic carbon in the deep soil is gradually held by mineral clay to form carbon with complex structure, so the carbon storage capacity is strengthened and organic carbon is difficult to leach. At the same time, cultivating will destroy the continuity of soil pores in the cultivated layer and between the cultivated layer and the lower layer, and produce a compact layer at the bottom of the cultivated layer, which is beneficial to the interception of organic carbon. With the deepening of soil layer, the hydrodynamic force gradually decreases, and the migration ability of organic carbon also gradually weakens, which leads to the accumulation of organic carbon.

• According to your suggestion, we have changed ＂SOC in 0-10cm surface layer migrated downward with irrigation infiltration and accumulated in middle soil＂ to ＂SOC in 0-10 cmsurface layer migrated downward with irrigation infiltration and accumulated in middle soil＂.
• According to your suggestion, we have changed ＂Callesen et al (Callesen et al., 2010) think that silt content is the key factor affecting organic carbon content.＂ to ＂Callesen et al. (2010)think that silt content is the key factor affecting organic carbon content＂.

Author Response File: Author Response.docx

Reviewer 2 Report

I thank the authors for bringing out such interesting topic. However, I have some comments: 

The methodology section is not clear. Did you collect samples from same location or nearby location? If you are collecting from same location, then the results will be different as the properties of imported material in the hole could produce different results. You must clearly articulate that issue. 

Also, what about the median sediment size, texture (other than reporting the % silt, clay, sand) and minerals. Since minerals or geology could have influence on the overall findings of your research. 

In results, I see only influence of irrigation has been reported. But nothing is said about the precipitation event. All of a sudden in the discussion section, I see you are writing about the influence of irrigation. Any specific reasons? 

Since you are saying it is an arid region, how come you are getting so many precipitation events? No discussion or data has been presented on that. 

The discussion section is not aligned with methodology and result section. You should not open a discussion without prior description. I also see you developed correlations, what is the p-value? Why you did not discuss on the correlations? Is it just for the seek of data presentation or future researchers can use those equations? You must say something on that. 

Statistical analysis e.g., the pairwise difference among these group could also be helpful for the reader (Mann-Whitney test) for understanding how those SOC are different and/or similar in different layers.

I made some other comments in the manuscript, please check. 

Best of luck! 

Comments for author File: Comments.pdf

English is good, however, in some places it requires editing. 

Author Response

Response to Reviewer #2

I thank the authors for bringing out such interesting topic. However, I have some comments: 

Thank you very much for reviewing our article. Your suggestions are very important for improving the quality of our article. We have explained the key issues you mentioned. The detailed explanations are as follows, and we hope to get your approval.

1. The methodology section is not clear. Did you collect samples from same location or nearby location? If you are collecting from same location, then the results will be different as the properties of imported material in the hole could produce different results. You must clearly articulate that issue.

According to your suggestion, we have explained the key issue you mentioned. We used a hand-held auger with a diameter of 6.9 cm to collect fresh soil samples from a 1m soil layer in the sample plot. The samples were collected in 0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm, 50-60 cm, 60-70 cm, 70-80 cm, 80-90 cm and 90-100 cm soil layers. During the sampling process, every time we take soil samples, we will clean the upper soil to prevent the upper soil from falling and other factors affecting the collection of the lower soil. 

The detailed revisions are as follows. On the basis of comprehensive consideration of the spatial pattern of topography and land use, a sample plot was selected in Beidan Village (38°79′N,103°23′E) in the middle of Minqin Oasis from April 2018 to October 2019. We used a hand-held auger with a diameter of 6.9 cm to collect fresh soil samples from a 1m soil layer in the sample plot. The samples were collected in 0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm, 50-60 cm, 60-70 cm, 70-80 cm, 80-90 cm and 90-100 cm soil layers. During the sampling process, every time we take soil samples, we will clean the upper soil to prevent the upper soil from falling and other factors affecting the collection of the lower soil. Make the sampling plan dense, before and after irrigation, sampling once before irrigation, and sampling continuously for five days after irrigation. Fill the collected soil samples into sample bottles, accurately locate the sampling points by GPS, and record the altitude and soil water content at the same time. The average temperature in the ground is 14.25. C, precipitation is mainly concentrated from June to September. The soil texture within 1m in the sample plot is mainly loam and sandy loam (Table 1). The crops are mainly corn, the irrigation is mainly well water or canal water, and the irrigation method is ground flood irrigation. In the sampling period, there were 6 irrigation events, all of which were well water irrigation, and the irrigation amount was monitored by the intelligent water distributor terminal of HZQP-DIC card. The film coverage rate in the sample plot is between 80% and 85%.

2. Also, what about the median sediment size, texture (other than reporting the % silt, clay, sand) and minerals. Since minerals or geology could have influence on the overall findings of your research.

According to your suggestion, we have explained the key issue you mentioned.Our study site is located in Beidan Village (38°79′N,103°23′E)，the geological characteristics are Gravel/ Pebble/ Coarse sand. The specific Clay, Silt, Soil bulk density features are shown in Table 1. We did not find mineral or geological impact on the results when calculating SOC.

3. In results, I see only influence of irrigation has been reported. But nothing is said about the precipitation event. All of a sudden in the discussion section, I see you are writing about the influence of irrigation. Any specific reasons?

According to your suggestion, we have explained the key issue you mentioned. Because precipitation belongs to another form of irrigation water, the impact of precipitation on SOC was added in the discussion to make our research more complete. Water is the limiting factor of plant production in arid areas, because a small increase of water can significantly stimulate biological productivity and contribute to SOC accumulation. The results of this study showed that SOC in irrigation area increased significantly with the increase of precipitation, SOC distribution was positively correlated with precipitation. In addition, precipitation, plastic film mulching, soil physical and chemical properties and other environmental factors were important factors to promote SOC content migration and change. 

The detailed revisions are as follows. There were significant differences in the migration amount of SOC under the same depth and different irrigation amounts. Among them, the 0-30cm surface layer soil was most affected by irrigation, and the leaching rate increased with the increase of irrigation amount. The migration amount of SOC content under six different irrigation conditions was 1.98g/kg, 1.58g/kg, 1.86g/kg, 1.46g/kg, 0.90g/kg and 0.15g/kg, respectively, and the SOC leaching rate was between 13.5% and 36.8%. The migration amount of SOC in the middle soil 30-70cm under six different irrigation conditions was negative, which was -0.15, -1.13, -1.40, -0.22, -1.54, 0.40 and -1.55, respectively, which indicated that the organic carbon lost in the upper layer is trapped in this layer, resulting in the accumulation of organic carbon. Among them, except for the fifth irrigation, the SOC content in the sample plots was in a leaching state, and the SOC content in the other five irrigation plots was in a cumulative state. The highest cumulative rate appeared at I₃, and the cumulative rate was 95.28%, indicating that moderate irrigation was helpful to the accumulation of organic carbon in the middle soil. In addition, in arid ecosystems, precipitation can reduce soil water stress (Chen et al., 2016), increase soil nutrients, increase biomass of vegetation types, and thus promote an increase in SOC storage.

References

Chen, C. P., Juang, K. W., Cheng, C. H., & Pai, C. W. (2016). Effects of adjacent land-use types on the distribution of soil organic carbon stocks in the montane area of central Taiwan. Botanical studies, 57(1), 1-8.

4. Since you are saying it is an arid region, how come you are getting so many precipitation events? No discussion or data has been presented on that.

According to your suggestion, we have explained the key issue you mentioned. Our study area is located in the middle and lower reaches of arid inland rivers. The oasis has a temperate continental desert climate with a temperature difference of 25.2 ◦C between day and night, an average annual temperature of 7.8 ◦C, an annual average wind speed is 2.8 m/s, sunshine hours of 3073.5 h and a frostfree period of 162 days. The annual precipitation is 113.2 mm and the annual evaporation is 2675.6 mm, which is one of the extremely arid regions in China. In the basin, the precipitation is mainly concentrated from June to September, but the amount of precipitation is less each time.

5. The discussion section is not aligned with methodology and result section. You should not open a discussion without prior description. I also see you developed correlations, what is the p-value? Why you did not discuss on the correlations? Is it just for the seek of data presentation or future researchers can use those equations? You must say something on that.

According to your suggestion, we have explained the key issue you mentioned. Because precipitation belongs to another form of irrigation water, the impact of precipitation on SOC was added in the discussion to make our research more complete. In addition, plastic film mulching, soil physical and chemical properties and other environmental factors were important factors to promote SOC content migration and change. We recalculated the P-values in Fig. 6 and Fig. 8, and modified Fig. 6 and Fig 8. The detailed revisions are as follows.

 

Fig. 6 Influence of precipitation on soil organic carbon

 

Fig. 8 Correlation between soil particle size, soil bulk density and SOC

6. Statistical analysis e.g., the pairwise difference among these group could also be helpful for the reader (Mann-Whitney test) for understanding how those SOC are different and/or similar in different layers.

According to your suggestion, we have carried out Mann-Whitney test on the relevant content in the manuscript，it helps the reader understand how those SOC are different and/or similar in different layers.

7. I made some other comments in the manuscript, please check.

According to your suggestion, we have explained the key issue you mentioned. The detailed explanation is as follows.

• many scholars at home and abroad have. What do you mean by home and abroad?

What we mean is that both foreign and domestic scholars have explored the migration of soil organic carbon under different irrigation conditions and have achieved good results.

• Some scholars believe that irrigation is the most potential management measure for carbon sequestration. Any references?

According to your suggestion, we have added references from previous studies. The detailed revisions are as follows.

Some scholars believe that irrigation is the most potential management measure for carbon sequestration (Adhikari et al., 2017).

• (Denef et al., 2008). Wrong ref style.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows. We have changed ＂For example, Denef et al. (2008) studied in arid areas of the United States, showing that the SOC content in irrigated areas is significantly higher than that in non-irrigated fields (Denef et al., 2008)＂ to ＂For example, Denef et al. (2008) studied in arid areas of the United States, showing that the SOC content in irrigated areas is significantly higher than that in non-irrigated fields＂.

• Fallahzade and Hajabbasi.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows. We have changed ＂A survey of Iran by Fallahzade and Hajabbasi showed that SOC content increased significantly after desert was transformed into irrigated farmland (Fallahzad et al., 2012)＂ to ＂A survey of Iran showed that SOC content increased significantly after desert was transformed into irrigated farmland (Fallahzad et al., 2012)＂.

• Tang Guang Mu et al

According to your suggestion, we have revised the sentence. The detailed revisions are as follows. We have changed ＂Tang Guang Mu et al＂ to ＂ Tang et al. (2010)＂.

• The samples were collected in. Are you collecting the samples from same auger hole location or side by side? If you are collecting from same location, how are you replacing the soil samples? No detail write up on this issue. To my knowledge, if you replace soil, the characteristics is changed. Also, if you work with natural soil, the heterogeneity is to much, which can also impact the SOC content. How did you address that?

According to your suggestion, we have explained the key issue you mentioned. We used a hand-held auger with a diameter of 6.9 cm to collect fresh soil samples from a 1m soil layer in the sample plot. The samples were collected in 0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm, 50-60 cm, 60-70 cm, 70-80 cm, 80-90 cm and 90-100 cm soil layers. During the sampling process, every time we take soil samples, we will clean the upper soil to prevent the upper soil from falling and other factors affecting the collection of the lower soil. In the study area, there is little difference in the physical and chemical properties of natural soil, as shown in the table 1.

Table 1. Physical and chemical properties of sample soil

Soil depth (cm)	Clay (%)	Silt (%)	Sand (%)	Soil bulk density (g/cm2)	Porosity(%)	pH	EC (μs/cm)
0-10	10.2	25.77	60.95	1.052	61	7.87	2.48
10-20	9.94	27.76	59.79	1.194	58	7.89	2.46
20-30	10.33	34.23	56.34	1.398	54	7.93	2.43
30-40	15.48	58.69	22.04	1.18	51	7.96	2.39
40-50	10.01	33.09	53.87	1.14	47	8.19	2.34
50-60	16.21	55.83	23.6	1.206	44	8.21	2.23
60-70	34.34	42.98	14.36	1.208	42	8.24	2.14
70-80	26.09	38.96	29.88	1.106	41	8.27	1.99
80-90	11.75	28.72	56.11	1.2	39	8.29	1.95
90-100	7.21	21.97	69.08	1.372	36	8.32	1.91

• ground flood irrigation. Check the name.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows. We have changed ＂ground flood irrigation＂ to ＂flood irrigation＂.

• bulk density. It has standard symbol.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows. We have changed ＂soil bulk density (RS)＂ to ＂soil bulk density (SBD)＂.

• Please check the equation.

 

According to your suggestion, we have revised the sentence. The detailed revisions are as follows.

 

• (Wang et al., 2018). wrong reference.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows. We have changed ＂(Wang et al., 2018): clay (<2um), silt (2-50um) and sand (50-1000um).＂ to ＂Clay (<2um), silt (2-50um) and sand (50-1000um) (Wang et al., 2018).＂.

Author Response File: Author Response.docx

Reviewer 3 Report

The presented research topic complements the current knowledge. Interesting research, but presented chaotically. He proposes to introduce a modification of the conducted analysis and the necessary additions.

In the submitted PDF file, the lack of line numbering makes it difficult to make a readable review.

Abstract   Point 3 of the abstract, from which we learn that significantly greater SOC accumulation occurred in the 10-70 cm layer, contradicts the information earlier that the greatest SOC leaching occurred in the 0-30 cm layer. One could just as well write that the greatest SOC occurred in the 0-70 cm layer.

 

Point 3.1    The information presented that: "the amount of irrigation was monitored by the smart terminal of the water distributor" is too general. Here I ask for information on the irrigation rates applied, which will allow an objective analysis of the distribution and migration of SOC in the analyzed soil profiles later in the article. We have brief information on the applied doses only in para. 4.3. The doses proposed in the experiment are relatively high, so the migration of SOC will be strongly correlated with them. In this part of the article, please tell me on what basis the irrigation doses were determined (provide assumptions and formulas).   I believe that the application of six consecutive doses of similar size, caused forced migration and accumulation of SOC. The question is whether, under the conditions of the experiment, the doses should not have been varied to a greater extent.  This section lacks description, general principles of  irigation

In point 3.2 4, please provide the entire range ( e.g., in a tabular list) of soil analyses performed. Under irrigated conditions, the migration of SOC will also be significantly affected by parameters such as porosity and soil skeletal content, which can vary greatly in the soil profile.

Point  3.2.5     Please include a tabular summary of meteorological conditions (precipitation and temperature) from the study period against any multi-year period (e.g., on a monthly basis).

In point 4.1   The description that something is decreasing , and then increasing, and then decreasing again is too general, please provide an analysis based on specific values, or in percentage terms.  Please avoid such general descriptions in the article.

In point. 4.2 we get information that carbon migration is dependent on the amount of irrigation, requires a broader analysis.  This item also contains single information about the calculated correlations. Please feel free to describe them in more detail. 

Information "The migration amount of SOC content under six different irrigation conditions was 1.98g/kg, 1.58g/kg, 1.86g/kg, 1.46g/kg, 0.90g/kg and 0.15g/kg, respectively, and the SOC leaching rate was between 13.5% and 36.8%",  is not very readable and requires a broader analysis.

Figure 6 A lacks a description of the SOC accumulation layer

  Fig. 7 shows that mulching with plastic film, increased the average SOC content in irrigation I-1 I-2 and I-5, also in the 0-10 layer, while the content of the article shows otherwise.

The statement in the final conclusions that the experiment was carried out in different hydration conditions is imprecise. Final conclusions should be limited only to new information resulting from the conducted experiment.

There is a little information chaos in part of the article, which makes it difficult to read.

Author Response

Response to Reviewer #3

The presented research topic complements the current knowledge. Interesting research, but presented chaotically. He proposes to introduce a modification of the conducted analysis and the necessary additions.

Thank you very much for reviewing our article. Your suggestions are very important for improving the quality of our article. We have explained the key issues you mentioned. The detailed explanations are as follows, and we hope to get your approval.

1. In the submitted PDF file, the lack of line numbering makes it difficult to make a readable review.

We apologize for not adding the line number in the PDF file. According to your suggestion, we have added the line number in the resubmitted manuscript for your review.

2. Abstract Point 3 of the abstract, from which we learn that significantly greater SOC accumulation occurred in the 10-70 cm layer, contradicts the information earlier that the greatest SOC leaching occurred in the 0-30 cm layer. One could just as well write that the greatest SOC occurred in the 0-70 cm layer.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows.

Due to the influence of soil infiltration rate under water, SOC content in different irrigation periods showed that the greatest SOC occurred in the 0-70 cm layer, and SOC content in soil was basically the same as that in non-irrigated areas on the fifth day after irrigation.

3. Point 3.1 The information presented that: "the amount of irrigation was monitored by the smart terminal of the water distributor" is too general. Here I ask for information on the irrigation rates applied, which will allow an objective analysis of the distribution and migration of SOC in the analyzed soil profiles later in the article. We have brief information on the applied doses only in para. 4.3. The doses proposed in the experiment are relatively high, so the migration of SOC will be strongly correlated with them. In this part of the article, please tell me on what basis the irrigation doses were determined (provide assumptions and formulas). I believe that the application of six consecutive doses of similar size, caused forced migration and accumulation of SOC. The question is whether, under the conditions of the experiment, the doses should not have been varied to a greater extent. This section lacks description, general principles of  irigation.

According to your suggestion, we have explained the key issue you mentioned. The detailed explanations are as follows.

HZQP-DIC card smart water distribution terminal is an intelligent water meter. The intelligent water meter is composed of a transmitter based meter, a controller, a control valve, a card holder and a radio frequency card. It uses the radio frequency card as the data transmission medium,and transmits the irrigation command to the water meter through the card into the water meter card holder, realizes the control of the water meter on-off valve, and displays the amount of water and the working status of the water meter. Farmers only need to swipe their cards to operate the irrigation well to take water and record the irrigation-water volume when the water is cut off. The monthly irrigation amount is determined by local farmers with farming experience based on the actual water demand for crop growth. Our irrigation rate can be calculated by dividing the actual irrigation amount by the irrigation time.

4. In point 3.2.4, please provide the entire range ( e.g., in a tabular list) of soil analyses performed. Under irrigated conditions, the migration of SOC will also be significantly affected by parameters such as porosity and soil skeletal content, which can vary greatly in the soil profile.

According to your suggestion, we have added information. The detailed revisions are as follows.

Table 1. Physical and chemical properties of sample soil

Soil depth (cm)	Clay (%)	Silt (%)	Sand (%)	Soil bulk density (g/cm2)	Porosity(%)	pH	EC (μs/cm)
0-10	10.2	25.77	60.95	1.052	61	7.87	2.48
10-20	9.94	27.76	59.79	1.194	58	7.89	2.46
20-30	10.33	34.23	56.34	1.398	54	7.93	2.43
30-40	15.48	58.69	22.04	1.18	51	7.96	2.39
40-50	10.01	33.09	53.87	1.14	47	8.19	2.34
50-60	16.21	55.83	23.6	1.206	44	8.21	2.23
60-70	34.34	42.98	14.36	1.208	42	8.24	2.14
70-80	26.09	38.96	29.88	1.106	41	8.27	1.99
80-90	11.75	28.72	56.11	1.2	39	8.29	1.95
90-100	7.21	21.97	69.08	1.372	36	8.32	1.91

5. Point 3.2.5 Please include a tabular summary of meteorological conditions (precipitation and temperature) from the study period against any multi-year period (e.g., on a monthly basis).

According to your suggestion, we have added a tabular summary of meteorological conditions (precipitation and temperature) from the study period.

Table 2. Monthly precipitation and average temperature in the study area

		Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
2018	AP (mm)	3.5	1.1	0	14.2	6	12	25.9	50	24	7	0.3	1.1
	MAT (℃)	-8.9	-4.1	8.8	13.1	18.9	24.2	25.6	23.1	16.1	8.8	1.7	-8.8
2019	AP (mm)	3.1	0	0	7.2	17.8	16.6	12.5	14.9	25.7	14.4	1.7	1.1
	MAT (℃)	-8	-3.8	5.4	14.8	16.4	22.4	24.4	23.7	19.1	9.3	1.6	-4.5

6. In point 4.1 The description that something is decreasing , and then increasing, and then decreasing again is too general, please provide an analysis based on specific values, or in percentage terms.  Please avoid such general descriptions in the article.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows.

Comparing the SOC content of soil before and after six irrigation events, it was found that irrigation increased the average SOC content of 0-100 cm soil layer in the sample plot (Fig.2). Before irrigation, the SOC content tend to be consistent with the increase of soil depth, that is, the SOC content at 0-30 cm decreased gradually with the increase of soil depth, and its minimum value was 3.25 g/kg. The SOC content below 30 cm had an M-shaped change pattern of "first increasing, then decreasing, then increasing and then decreasing", with the maximum value of 8.75 g/kg and the minimum value of 1.25 g/kg. The SOC content at 0-5cm surface layer was the highest, and its average value was more than 5 g/kg. After irrigation leaching, the organic carbon in each soil layer decreased first and then increased with the increase of soil depth, which mainly showed that SOC content in 0-30 cm surface layer decreased significantly compared with that before irrigation, and SOC content in 30-70 cm surface layer increased compared with that before irrigation, but SOC content in 70-100 cm bottom soil had no significant change.

7. In point. 4.2 we get information that carbon migration is dependent on the amount of irrigation, requires a broader analysis.  This item also contains single information about the calculated correlations. Please feel free to describe them in more detail. 

According to your suggestion, we have revised the sentence. The detailed revisions are as follows.

 As shown in Fig. 3, there were significant differences in migration amount of SOC at different depths under the same irrigation condition, and the migration amount of organic carbon in each soil profile gradually decreased with the increase of soil depth. There was a significant positive correlation between migration amount of SOC and irrigation amount in 0-30 cm of surface soil and 30-70 cm of middle soil (P<0.001, r=0.98), that is, the carbon leaching rate under high irrigation amount was higher than that under low irrigation amount, but there was no significant correlation between migration amount of SOC and irrigation amount in 70-100 cm of bottom soil (P<0.5, r=0.12). Migration amount of SOC at 0-30 cm of surface soil was significantly higher than that at 30-70cm of middle layer and 70-100 cm of bottom layer, which indicated that SOC was in leaching state after irrigation at 0-30 cm of surface soil, and carbon lost from surface layer was trapped by soil layer at 30-70 cm, which made carbon deposit at 30-100cm, so the SOC content of soil layer at 30-70 cm after irrigation was significantly higher than that of surface soil.

8. Information "The migration amount of SOC content under six different irrigation conditions was 1.98g/kg, 1.58g/kg, 1.86g/kg, 1.46g/kg, 0.90g/kg and 0.15g/kg, respectively, and the SOC leaching rate was between 13.5% and 36.8%",  is not very readable and requires a broader analysis.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows.

There were significant differences in the migration amount of SOC under the same depth and different irrigation amounts. Among them, the 0-30cm surface layer soil was most affected by irrigation, and the leaching rate increased with the increase of irrigation amount. Under six different irrigation conditions, the total migration amount of SOC content at 0-100 cm was 1.98g/kg, 1.58g/kg, 1.86g/kg, 1.46g/kg, 0.90g/kg and 0.15g/kg, respectively. The maximum leaching rate of SOC was 36.8%, the minimum leaching rate was 13.5%, and its average leaching rate was 23.4%. The migration amount of SOC in the middle soil 30-70cm under six different irrigation conditions was negative, which was -0.15, -1.13, -1.40, -0.22, -1.54, 0.40 and -1.55, respectively, which indicated that the organic carbon lost in the upper layer is trapped in this layer, resulting in the accumulation of organic carbon. Among them, except for the fifth irrigation, the SOC content in the sample plots was in a leaching state, and the SOC content in the other five irrigation plots was in a cumulative state. The highest cumulative rate appeared at I₃, and the cumulative rate was 95.28%, indicating that moderate irrigation was helpful to the accumulation of organic carbon in the middle soil. In addition, in arid ecosystems, precipitation can reduce soil water stress (Chen et al., 2016), increase soil nutrients, increase biomass of vegetation types, and thus promote an increase in SOC storage.

9. Figure 6 A lacks a description of the SOC accumulation layer.

According to your suggestion, we have revised the Fig.6. The detailed revisions are as follows.

 

Fig. 6 Influence of precipitation on soil organic carbon

10. 7 shows that mulching with plastic film, increased the average SOC content in irrigation I-1 I-2 and I-5, also in the 0-10 layer, while the content of the article shows otherwise.

According to your suggestion, we checked the manuscript and the normalization of Figure 7. Plastic film mulching leads to SOC consumption and a decrease in SOC content, so we revised Fig. 7, the detailed revisions are as follows.

 

Fig. 7 Changes of SOC content with and without plastic film

11. The statement in the final conclusions that the experiment was carried out in different hydration conditions is imprecise. Final conclusions should be limited only to new information resulting from the conducted experiment.

According to your suggestion, we have revised the sentence. The detailed revisions are as follows.

  In this study, the leaching characteristics and migration laws of soil organic carbon under different irrigation conditions were systematically investigated in Minqin Oasis, and the leaching amount of SOC under different irrigation amounts was quantified, and the process and mechanism of organic carbon loss under water erosion were discussed. The information resulting from the conducted experiment was that: (1) Irrigation increased the average SOC content at 0-100cm, and the SOC leaching migration was larger at 0-10cm. After irrigation, SOC migrated to deep soil, the accumulation depth of SOC increases with the increase of irrigation amount, and the greater the irrigation amount, the higher the carbon leaching rate. (2) After irrigation leaching, the organic carbon in each soil layer decreased first and then increased with the change of soil depth, which mainly showed that SOC content in 0-30cm surface layer was in a leaching state compared with that before irrigation, SOC content in 30-70cm surface layer was in a cumulative state, and SOC content in 70-100cm surface layer had no obvious change. (3) Under the same irrigation condition, the migration amount of SOC at different depths gradually decreased with the increase of soil depth. In different irrigation periods, SOC content showed the same change law with time, that is, SOC content in 0-70 cm soil layer was significantly higher than other soil layers in the first four days after irrigation, and SOC content in soil was basically the same as that before irrigation on the fifth day after irrigation. (4) In addition, precipitation, plastic film mulching, soil physical and chemical properties and other environmental factors were important factors to promote SOC content migration and change. Environmental factors had the most significant effect on SOC migration in the surface layer of 0-30 cm. Therefore, the accumulation of long-term measured data should be paid attention to in future research, and the influence of irrigation on SOC of different depth soil layers and the quantification of irrigation influence mechanism should be made clear. At the same time, the relationship among the influencing mechanisms should be deeply understood, and the contribution weight of soil change factors to SOC under the influence of irrigation should be determined.

12. There is a little information chaos in part of the article, which makes it difficult to read.

According to your suggestion, we have revised the logic and language of the manuscript, and improved the clarity of each figure. We hope that the revised manuscript can get your approval.

Author Response File: Author Response.docx