Risk of Secondary Soil Salinization under Mixed Irrigation Using Brackish Water and Reclaimed Water

Round 1

Reviewer 1 Report

The authors presented an interesting paper in which they studied the changes in soil when brackish or reclaimed water are used as an irrigation source. The topic fits the journal scope, and it is updated. In general terms, the results are well presented, and the paper is well structured. Nonetheless, some aspects should be improved in order to enhance the quality of the manuscript. Following, some recommendations are included:

Major issues:

Some information has to be added in Section2. Authors must justify the selection of 3 and 5 g of salts to generate the BW. Authors must justify how did they select the treatments. Authors should mention if RW has a constant level of ions along the period or a variation in its content. The same aspect must be analyzed for tap water.

Since experiments were performed under a greenhouse, which directly affects the evapotranspiration and the salinization process completely different from having the experiments outside the greenhouse, this fact must be highlighted in the introduction. In the discussion, authors can detail if other works have been performed in similar facilities or if experiments were conducted in the field.  

In discussion, authors can include information about the crop results in the different treatments.

Minor issues:

The paper needs some adjustments in terms of format to the Table. Some tables are divided into two pages, and others are difficult to read (see Table 3). In addition, capital letters should be used correctly. Check Table 1 “treatment” or “ solution” also check the same problem in Table 2.

In Figure 2, I suggest reshaping the Y-axis to maximize the visualization of differences among the pH values.

Author Response

Major issues: Some information has to be added in Section2. Authors must justify the selection of 3 and 5 g of salts to generate the BW. Authors must justify how did they select the treatments. Authors should mention if RW has a constant level of ions along the period or a variation in its content. The same aspect must be analyzed for tap water. Since experiments were performed under a greenhouse, which directly affects the evapotranspiration and the salinization process completely different from having the experiments outside the greenhouse, this fact must be highlighted in the introduction. In the discussion, authors can detail if other works have been performed in similar facilities or if experiments were conducted in the field. In discussion, authors can include information about the crop results in the different treatments. Reply: We are really appreciate your comments and suggestions. According to Cao et al. (2007), water with salinity levels of 2–5  g/L and 5–7  g/L accounts for 47.8 and 38.5% of this saline groundwater, respectively, in the Low Plain around the Bohai Sea. So, we select 3 g/L and 5 g/L brackish water. Brackish water is generated by adding sea salt to the freshwater according to Zhang et al. (2018). The salinity in freshwater (tap water) is very low, so its salt could be neglected. In addition, reclaimed water and tap water have a constant level of ions due to their stable sources, which we will mention in the revision. Yes, you are right. The salinization process completely different from the experiments outside the greenhouse. We have highlight that in the introduction. Also, the mixed irrigation using brackish water and reclaimed is hardly studied, and our research is just beginning. In the discussion, we add the results about the crop results. Due to our focus on soil salinization, only add the information about biomass of crop. 1. Cao, C. Y., K. J.Li, J. Y.Ma, and C. L.Zheng. 2007. Utilization status and development potential of shallow salt groundwater in the Hebei Lowland Plain. Anhui Agric. Sci. Bull.13 (18): 66–68. 2. Zhang, J.; Li, K.; Zheng, C.; Cao, C.; Sun, C.; Dang, H.; Feng, D.; Sun, J., Cotton Responses to Saline Water Irrigation in the Low Plain around the Bohai Sea in China. Journal of Irrigation and Drainage Engineering 2018, 144 (9), 04018027. Minor issues: The paper needs some adjustments in terms of format to the Table. Some tables are divided into two pages, and others are difficult to read (see Table 3). In addition, capital letters should be used correctly. Check Table 1 “treatment” or “ solution” also check the same problem in Table 2. In Figure 2, I suggest reshaping the Y-axis to maximize the visualization of differences among the pH values. Reply: Thank you for your comments, we are really sorry for our carelessness. We have adjusted the format to the table. Table, divided into two pages, is adjusted to a page. Soil salt content in table 3 is calculated by adding the soil soluble ions, in order to analyze soil salinization in unit of g/kg. We have checked table 1 and table 2, solution in table 1 is changed to mixed solution. In Figure 2, we accept the advice and reshape the Y-axis to maximize the visualization of differences among the pH values. Thanks very much for your working on our manuscript. Finally, we sincerely hope you can give us more valuable comments on this manuscript, you are a very excellent expert in this field, and we will try our best to improve the manuscript and hope it can published on this journal, and discuss the brackish water and reclaimed water irrigation with the researchers all over the world. Thank you and best regards. Yours sincerely, Chuncheng Liu, Bingjian Cui, Ketema Tilahun Zeleke, Chao Hu, Haiqing Wu, Erping Cui, Pengfei Huang, Feng Gao Corresponding author: Name: Feng Gao E-mail: [email protected]

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript entitled “Risk of Soil Secondary Salinization under Mixed Irrigation using Brackish Water and Reclaimed Water” reports the results of a research, having the objective to evaluate the effects of irrigation with unconventional water resources on soil properties. On a pot experiment, the authors studied the effects of brackish water at two different salt concentrations (3 and 5 g L^-1) and the mixing of brackish water with reclaimed water on soil properties. The topic is interesting and actual, especially with a view to identifying strategies for saving freshwater without losses of productions.

The authors provided an in-depth overview of the topic and clearly explained the objectives of the study. 

In my opinion the article has some weak point in methodology and presentation and discussion of results. Below I have provided some comments and remarks on the text. 

 At page 3, lines 127-142, the authors described the experimental trial in detail, but it is not very clear how they established the timing of the irrigation. Were soil moisture sensors installed in the pots? Moreover, in the Table 1 the authors did not present the experimental design, that is not specified (completely randomized design or randomized complete block design), but they reported the treatments compared, so also the title of the table 1 should be modified.

In the figure 1, the symbol θ (by convention it indicates the soil volumetric content of water) is improper, considering that the water content reported is expressed as a percentage of soil mass.

The figures 2, 3 and 4 are unclear. The authors should add a note to explain what means the different letter. For example: in figure 2, is the soil pH value in T1 treatment statistically equal to pH in the T2 treatment? in Figure 3b is the exchangeable Na in the T2 significantly higher compared all other treatments? But the letter “c” is missing. In my opinion, in these figures it is not necessary to repeat the data relating to the T7 and CK treatments.

In the figure 5, I suggest using two vertical axes, the principal axis with, for example, ESP and secondary axis with SAR.

At page 9 line 284: modify the sentence as following: since the SAR estimation was based on the ion content of 1:5 soil-to-water extract rather than saturated paste extract, it was unreasonable to use…

At page 10, line 302 delete “research” before “results”

The table 3 should be improved. The authors should add a note to better explain the data reported.

 

At page 11, lines 331-333, the sentence is not very clear. The ESP values in T2 (brackish water at 5 g L salt concentration), T4 and T6 were higher than the threshold (15%). The authors should explain better the concept.

As reported by the authors in the last paragraph of the discussions (pag. 11 lines 343-351), irrigation with saline water at the two concentrations causes a slight salinization, so in my opinion the authors should give more emphasis to this result always in perspective saving good quality water and sustainable agriculture.   

Decision: I believe that the paper should be published after minor revisions, predominantly in methodology and discussion of results. 

Author Response

Reviewer2: The authors provided an in-depth overview of the topic and clearly explained the objectives of the study. In my opinion the article has some weak point in methodology and presentation and discussion of results. Below I have provided some comments and remarks on the text. At page 3, lines 127-142, the authors described the experimental trial in detail, but it is not very clear how they established the timing of the irrigation. Were soil moisture sensors installed in the pots? Moreover, in the Table 1 the authors did not present the experimental design, that is not specified (completely randomized design or randomized complete block design), but they reported the treatments compared, so also the title of the table 1 should be modified. Reply: We are really appreciate your comments and suggestions, also very sorry for our poor description. At page3, lines 127-142 in the manuscript, some details are not very clear, which has been revised in the revision. The timing of the irrigation was established according to previous experiments of our workmates and soil moisture sensors are installed in previous experiments. In our experiments, soil moisture sensors are not installed, we refer to the experiences: in the early stage, irrigation was carried out approximately once every 2 days while in the later stage, irrigation was performed approximately once per day as the crop's water demand increased. Completely randomized design was used in our experiments. There are 3 replicates for each treatment. We revised the title of the table 1. In the figure 1, the symbol θ (by convention it indicates the soil volumetric content of water) is improper, considering that the water content reported is expressed as a percentage of soil mass. The figures 2, 3 and 4 are unclear. The authors should add a note to explain what means the different letter. For example: in figure 2, is the soil pH value in T1 treatment statistically equal to pH in the T2 treatment? in Figure 3b is the exchangeable Na in the T2 significantly higher compared all other treatments? But the letter “c” is missing. In my opinion, in these figures it is not necessary to repeat the data relating to the T7 and CK treatments. In the figure 5, I suggest using two vertical axes, the principal axis with, for example, ESP and secondary axis with SAR. Reply: Thank you for your comments. Indeed, the symbol θ usually presents the soil volumetric content of water. So, we delete the symbol in Figure 1. We add a note in figures 2,3 and 4, in order to explain the meaning of different letters: different lower case letters on boxplots represent the significant differences at the level of 0.05. The same as below. We add the letter “c” in Figure 3b. Repeat the data relating to the T7 and CK treatments is in order to display and compare intuitively. Of course, we can modify the figure if necessary. In addition, we accept the advice and modify the figure 5 using two vertical axes, the principal axis with ESP and secondary axis with SAR. At page 9 line 284: modify the sentence as following: since the SAR estimation was based on the ion content of 1:5 soil-to-water extract rather than saturated paste extract, it was unreasonable to use… At page 10, line 302 delete “research” before “results” The table 3 should be improved. The authors should add a note to better explain the data reported. Reply: We are really appreciate your comments and suggestions, also very sorry for our poor description. We have modified the contents at pages 9 and 10. Also, we have added a note below table 3 in order to better explain the data reported. At page 11, lines 331-333, the sentence is not very clear. The ESP values in T2 (brackish water at 5 g L salt concentration), T4 and T6 were higher than the threshold (15%). The authors should explain better the concept. As reported by the authors in the last paragraph of the discussions (pag. 11 lines 343-351), irrigation with saline water at the two concentrations causes a slight salinization, so in my opinion the authors should give more emphasis to this result always in perspective saving good quality water and sustainable agriculture. Reply: Thank you for your comments. At page 11, we delete the sentence “when the salinity of brackish water salinity is 5 g/L”, which is easy to misunderstand. In the last paragraph of the discussions, you are right, so we modified and gave more emphasis to this result always in perspective saving good quality water and sustainable agriculture. Thanks very much for your working on our manuscript. Finally, we sincerely hope you can give us more valuable comments on this manuscript, you are a very excellent expert in this field, and we will try our best to improve the manuscript and hope it can published on this journal, and discuss the brackish water and reclaimed water irrigation with the researchers all over the world. Thank you and best regards. Yours sincerely, Chuncheng Liu, Bingjian Cui, Ketema Tilahun Zeleke, Chao Hu, Haiqing Wu, Erping Cui, Pengfei Huang, Feng Gao Corresponding author: Name: Feng Gao E-mail: [email protected]

Author Response File: Author Response.docx