Review Reports

Round 1

Reviewer 1 Report

The Huang-Huai-Hai Plain is the most important crop growing area in China. Analyzing the water footprint of crop cultivation in this area is of great significance not only for China but also for other countries. On the whole, the language of this article is clear, the calculation method is appropriate, and it is in line with the scope of the journal.

The article has a few minor problems:

 

(1) There are so many references，and some ancient reference are unnecessary；

（2）In the conclusion, it is suggested that this technology can be promoted globally. However, the global analysis is not involved in the article, so it is suggested to delete this suggestion.

Author Response

please see the attached file

Author Response File: Author Response.docx

Reviewer 2 Report

This study presents an interesting comparison between the traditional cultivation method and low nitrogen fertilizer cultivation for major crops in the HHH region. I only have a few suggestions.

1. ETaw, ETc and Er are defined twice (pages 158, 171, and 175; pages 199-200). Remove the redundancy.

 2. Equations 4-5 need units (Volume/mass).

3. lines 201-214. The nitrogen leaching factor of 6.04% for the entire region, regardless of soil type, land slope, groundwater depth, and other factors would be oversimplifying. If field data are not available, authors may consider a sensitivity analysis. 

4. Figure 3. Add "traditional crop cultivation" into the caption because green cultivation may affect ETaw.

5. Lines 241-242. "less N fertilizer application decreased crop yields by 3-13% relative to traditional planting". How much less N fertilizer inputs for the crops in Green cultivation? Without a quantitative measure of N reduction, it is difficult to make sense of the yield drop. I didn't see N reduction levels for each crop in the green cultivation in the manuscript. N input is critical to crop water requirements.

6. How was average crop WF derived? does it consider or weighted by the planting acreages?

7. Figure 5. Why is it that the maximum value (upper bar) of blue WF under Green increased while the average point remains similar to Traditional? Please also add a legend for bars, and circles.

8. It is interesting to see that farmers are willing to sacrifice 10% yield loss to save ~ 50% of irrigation water for maize in the HHH region. Water price must be quite high vs. the cost of maize, or farmers received financial support from other sources to adopt Green cultivation. The economic side of the equation could also be discussed.

 

 

Author Response

please see the attached file

Author Response File: Author Response.docx

Reviewer 3 Report

The paper presents the important issue of the water footprint assessment of green and traditional cultivation of crops in the Huang-Huai-Hai farming region. The study systematically evaluated and compared the water footprint (WF) including WFblue, WFgreen and WFgrey of eight crops with wheat, maize, and rice, sweet potato, soybean, millet, mung bean and sorghum under green and traditional cultivation in the Huang-Huai-Hai farming region. The data came from 252 onsite questionnaires conducted in 2018 for land under green and traditional cultivations from 19 green planting companies and farming cooperatives, with green food production certification authorized by the China government. Specific comments: Add some more information about generalizable framework. Add references to the equations if possible. Are there concrete steps that can be recommended and how generalizable are the findings? Please  clarify the source of data clearly.Can they be applied to other areas? How dependent are they to specific characteristics of the region under examination? Conclusion is there any limitation? Is there any knowledge gap? Is there any room for further enquiries? If so, consider it in the discussion and the conclusion point. 

Author Response

please see the attached file

Author Response File: Author Response.docx