Optimizing the Cropland Fallow for Water Resource Security in the Groundwater Funnel Area of China

Round 1

Reviewer 1 Report

The paper is well written

Author Response

Thanks for your agreement to our paper.

Reviewer 2 Report

 This paper has developed a decision-making system to increase water productivity. In a general view, the article has an acceptable connection with the special issue. From the point of view of the quality of the figures and structure of the article, it seems to be of interest. But there are some concerns that need to be addressed. Therefore, my opinion is major revision.

In the abstract of the article, it is better to refer to the quantitative results. What effect energy optimization has had on the amount of irrigation consumption or similar results should be presented quantitatively.

The introduction is rather long. The main concepts related to the research are reviewed and other content can be removed.

All crops pruduction in this area is just for 3 crops? it seems that the difference between scenarios is not consistent with other plants. This item should be re-evaluated

The conclusion section has been able to clearly show the summary and objectives of the research. You should also consider the managerial implications and future research.

 

Author Response

Reviewer #2's Review for land-2173197 :
Comments to the author:

This paper has developed a decision-making system to increase water productivity. In a general view, the article has an acceptable connection with the special issue. From the point of view of the quality of the figures and structure of the article, it seems to be of interest. But there are some concerns that need to be addressed. Therefore, my opinion is major revision.

Answers：Thanks for your agreement.

 

In the abstract of the article, it is better to refer to the quantitative results. What effect energy optimization has had on the amount of irrigation consumption or similar results should be presented quantitatively.

Answers：Thanks for your suggestion. In abstract, we quantify the results of cultivated land fallow “quality”, “quantity” and “position”. We aimed to prove that there are differences in the cropland area and position between current fallow cropland and predicted fallow cropland. However, calculating the consumption of irrigation water after the optimization, which need to consider crop evapotranspiration, specific yield and other factors, so this study not present the relative result and take it as further work in discussion. “The effect of fallow land on groundwater resources should be evaluated combining with corresponding models”.

 

The introduction is rather long. The main concepts related to the research are reviewed and other content can be removed.

Answers：Thanks for your suggestion. We have carefully revised the introduction to simplify the relevant content and the introduction has deleted from 66 lines to 50 lines.

“The global water demand has tripled since the 1950s, but the availability of fresh water has been declining [1]. Water scarcity can reduce crop yields and adversely affect food security [2]. Irrigated agriculture is the main consumer of water resources, accounting for about 80% of global water use [3-4]. Many of the world’s major aquifers that support irrigated agriculture are being depleted at a rapid rate [5-6]. Long-term overexploitation of groundwater leads to a decline in the regional groundwater level, land subsidence and seawater intrusion. The confined water is a non-renewable resource, which is difficult to recover in a short time [7-8]. Therefore, it is urgent to take actions to deal with the problem of groundwater overexploitation.

The cropland fallow is a favorable measure to solve the problems of overexploitation of groundwater. It performs well in effective environmental conservation with lower cost compared with other land protection measures [9]. Many researches have shown that the fallow cropland can regulate grain yield, improve soil nutrient content, conserve water sources, and enhance cropland productivity [10-13]. Cropland fallow policy is a useful way to ensure the effect of cropland fallow [14]. For example, the United States implemented a land fallow protection plan (Conservation Reserve Program, CRP) in the 1930s; The European Union (EU) implemented a voluntary cropland fallow project in the 1980s [15-16]. These project aims to address the problem of food overproduction and low farmer incomes. However，little attention has paid to formulate policies for mitigating over-extraction of groundwater.

The North China Plain (NCP) is an important production area for winter wheat and summer maize, which plays an important role in food security of China. In the meanwhile, it has become the world’s largest groundwater funnel area in 2011 [17-19]. The water consumption of winter wheat and summer maize is approximately 400mm and 500mm, respectively, more than the annual precipitation of NCP (630mm) [20-21]. Xu et al. (2005) showed that irrigation demand of agricultural water is the main reason of the decline of groundwater [22]. Thus, decreasing the consumption of groundwater while ensuring the food security has become a great challenge. A series of policies and laws about the cropland fallow have been introduced successively in China to solve this problem. In 2014, the “No. 1 central document” proposed to carry out cropland fallow pilot projects and NCP was selected as one of the pilot areas. In November 2015, the government formulated the land fallow policy to support the socio-economic development in the upcoming Thirteenth Five-Year Plan [23]. With the implementation of the fallow policy, a growing number of  studies were conducted to reveal farmers’ responses to fallow policy, irrigation strategy optimization, and the impact of the fallow policy on groundwater or food security [23-25]. For example, Xie et al. (2018) discussed the farmers’ responses and the influencing factors for the winter wheat fallow policy in the Hebei groundwater funnel area of China and showed that the proportion of farmers and per capita area of cropland had a significant impact on support for the fallow policy [24].Ti et al. (2021) results showed that the winter fallow acreage should be expanded to maintain the groundwater table [19]. However, the research on the selection of the fallow location in areas where groundwater is overexploited is relatively lacking.

Quzhou County is a typical agricultural production area in the North China Plain, the average annual groundwater overexploitation is 1.64×10⁷ m³ [26]. The fallow pilot area has increased from 666.67 hm² in 2014 to 2900 hm² in 2019 under the support of national policies in Quzhou County [27]. The implementation of the cropland fallow pilot program was expected to have a positive impact on reducing the consumption of groundwater resources by agricultural irrigation. However, the groundwater level monitoring data showed that the groundwater level did not rise significantly but continued to fall downward, indicating the poor effectiveness of current fallow cropland [28]. Therefore, it is urgent to identify the reasonable fallow areas and establish a scientific fallow program based on the groundwater severity. Thus, this study aims to (1) analyze fallow urgency using IPLI and SDGCR indicators and quantify the fallow area at county level (2) analyze the matching situation between the current fallow land and the predicted fallow land.

 

All crops production in this area is just for 3 crops? it seems that the difference between scenarios is not consistent with other plants. This item should be re-evaluated

Answers：Thanks for your suggestion. We added the sentence “According to the survey and official documents, the main crops in Quzhou County are winter wheat, summer maize and cotton, and the sown area accounts for 81.8% of the total cropland.” In addition, the water demand of these three crops is relatively large in all crops, so we choose these three crops to assess the irrigation water’ demand and supply.

 

The conclusion section has been able to clearly show the summary and objectives of the research. You should also consider the managerial implications and future research.

Answers：Thanks for your suggestion. We added the sentence “This research can provide methods and ideas for accurately formulating the cultivated land fallow program; more research perspectives (society, economy, and ecology) are suggested to be considered and integrated for making the fallow program of multi-objective synergy in future research work.”

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions

The manuscript entitled “Cultivated land fallow plan for water resource security in the groundwater funnel area of China” investigated the land area for water resource security of China. The manuscript has a better organisational structure and includes pertinent conceptual information. But there are lots of typological errors in the manuscript, which need correction, starting from author's abbreviated symbols to lots in the running text. I have some comments here that the author must revise:

1.  Some more recent 2022 literature reviews need to be incorporated to highlight areas for future study and call attention to research hypotheses.

2. The exact study sites should be located on map, to give a clear picture of the study area.

3. Methodology section needs slight improvement.

4. Authors should make a clear distinction between results and discussion. There is some discussion in this section rather than a statement of the results of the analysis. The author must revise it carefully.

5. The discussion section needs to go deeper and more systematically and add some references.

6. The conclusion does not describe the specific conclusions obtained in the article, nor does it have specific data support, which is rather general. This part needs to be reorganized. What are the advantages and disadvantages of this study?

I suggest an improvement of the manuscript before acceptance.

 

 

 

Author Response

Reviewer #3's Review for land-2173197 :
Comments to the author:

The manuscript entitled “Cultivated land fallow plan for water resource security in the groundwater funnel area of China” investigated the land area for water resource security of China. The manuscript has a better organisational structure and includes pertinent conceptual information. But there are lots of typological errors in the manuscript, which need correction, starting from author's abbreviated symbols to lots in the running text. I have some comments here that the author must revise:

Answers：Thanks for your suggestion. We revised the typological errors in the manuscript carefully.

1. Some more recent 2022 literature reviews need to be incorporated to highlight areas for future study and call attention to research hypotheses.

Answers：Thanks for your suggestion. We added the reference Das, D.M. et al. (2022), Móricz N, (2012), and Lu et al.(2019) in future study. “The effect of fallow land on groundwater resources should be evaluated combining with corresponding models.”, “The calculation method of the amount of fallow cropland should be further optimized. The methods to properly and accurately determine the area of cropland fallow need to be explored. For example, the regional hydrogeological characteristics of key aquifers should be considered” “the research scope should be expanded to increase the urgency determination of fallow cropland. To make the cropland fallow programs more universal, different cropland fallow programs should be formulated according to the characteristics of different regions. For example, heavy metal pollution of farmland should focus on pollutants types, pollution degree, and crops with high biomass and cumulative absorbing effects.”

 

2. The exact study sites should be located on map, to give a clear picture of the study area.

Answers：Thanks for your suggestion. We marked the exact study site on map.

 

3. Methodology section needs slight improvement.

Answers：Thanks for your suggestion. We added the 2.4.1.1, 2.4.1.2 and 2.4.1.3 to make the structure clearly. In addition, we deleted and added the above sentences.

Delete: “Quzhou County is located in an area of groundwater resource shortage, where the agricultural irrigation water is mainly from shallow groundwater, and the shallow groundwater has become the main factor restricting the sustainable development of cultivated land in Quzhou County. There are many methods used to reflect the changes in groundwater resources.”, “At present, there are many methods for predicting the amount of cultivated land retained.”

Add: “So the formulations of W_s and W_r are as follows”, “According to the survey and official documents, the main food crops in Quzhou County are wheat, maize and cotton, and the sown area accounts for 81.8% of the total cropland(http://www.qzx.gov.cn/xxgk-show-102.html)”

 

4. Authors should make a clear distinction between results and discussion. There is some discussion in this section rather than a statement of the results of the analysis. The author must revise it carefully.

Answers：Thanks for your suggestion. We revised and deleted the section which belongs to discussion rather than that in results carefully.

“3.1.1. Irrigation profit-loss index (IPLI)

Based on the analysis of the irrigation water requirements of the main crops in Quzhou County in 2018, the IPLI was calculated. The results showed that the IPLI value of winter wheat is 0.1173 (Table 5), which means the irrigation water is in short supply during the growing season. In contrast, the IPLI values of summer maize and cotton are -0.9849 and -0.0071, respectively. These results show that corn and cotton’s irrigation is excessive supply, resulting in water resources waste.

3.1.2. Shallow groundwater depth change rate (SGDCR)

By analyzing the SGDCR results from the trend analysis chart from a spatial perspective (Fig. 5), we found that the groundwater depth decreases rapidly from north to south and from west to east. Based on the current situation of shallow groundwater re-sources in Quzhou County the depth to shallow groundwater in the south and east is deeper than that in the north and west.

3.1.3. Classification of the urgency of fallow cultivated land

The spatial overlap of IPLI and SGDCR lines can better perform the urgency of fal-low cropland and was shown in Fig. 6(a). The results showed that the urgency level of cropland fallow in Quzhou County gradually decreased from south to north.

In order to express the urgency of fallow cropland in Quzhou County, we divided the urgency of fallow cropland into five levels from the level 1 fallow area (the strongest urgency of fallow), to the level 5 fallow area (the weakest degree of cropland fallow). Overall, the urgency level of fallow is high in the south and low in the north (Fig. 6(b)). The strongest urgency of fallow area (level 1) is mainly distributed in towns of Yizhuang, Houcun, Baizhai, and Dahedao; the weakest degree of cropland fallow (level 5) area is mainly distributed in towns of Disituan and Henantuan town.

3.2.1. Cultivated land fallow area

The GM (1,1) gray prediction model after verification was used to predict the re-sults of related indicators of cropland holdings in Quzhou County in 2018; the basic in-formation was shown in Table S1. The cropland holding amount of Quzhou County is 63610.712 hm². According to official figures, and the predicted fallow cropland area is 4089.288 hm² under the premise of ensuring food security, which is 1189.288 hm2 more than the current cropland fallow area, with 2900 hm2 , according to government data (Fig. 7).

3.2.2. Space allocation of fallow land

In 2018, the fallow cropland plots in Quzhou County are mainly distributed in Yizhuang, Houcun, Nanliyue, Huaiqiao, Disituan, Henantuan, Baizhai, and Quzhou towns, which is a total of 8 townships involving 17 administrative villages (Fig. 7(a)). According to the degree of urgency of the cropland fallow, the areas of different levels of urgency were counted (Table S2) and combining the cropland fallow area (2900 hm²), cropland the selected cropland for fallow is concentrated in Yizhuang and Houcun towns, involving 9 administrative villages (Fig. 7(b)). By comparing Fig. 7(a) and Fig. 7(b), the original fallow plots in Quzhou County are scattered and the theoretical fallow land distribution is more concentrated and located in the places where water re-sources are scarce.”

 

5. The discussion section needs to go deeper and more systematically and add some references.

Answers：Thanks for your suggestion. We adjusted the position and expression of some sentences and added some references in discussion. “Research by Song et al (2022) showed that fallow is closely related to topographic factors such as altitude [37]. Mountainous areas are prone to farmland abandonment after the land fallow in south China [38-39]. In contrast, in the relatively flat plain, farmers take the initiative to apply for fallow to obtain compensation for fallow. The occurrence of fallow is largely related to the spontaneous behavior of farmers [40].”, “In fact, the spatially optimal allocation of fallow land should combine the fallow urgency level and fallow area.”

 

6. The conclusion does not describe the specific conclusions obtained in the article, nor does it have specific data support, which is rather general. This part needs to be reorganized. What are the advantages and disadvantages of this study?

Answers：Thanks for your suggestion. We added the data support and reorganized the conclusion. “Water resources are vital to regional sustainable development, especially in agricultural production areas. Facing the increasingly severe shortage of groundwater re-sources, the fallow of cropland is a favorable measure. At present, the cropland fallow program is relatively rough, and related studies have not specifically refined the cropland fallow urgency, area and position. To meet this gap, this study selects Quzhou County, a county with severe water shortage and a fallow pilot county, to analyze the urgency of the fallow of cropland, where should be fallowed and how much area should be fallowed. Our results showed that the urgency of fallow can be deter-mined using IPLI and SGDCR. The area of cropland fallow obtained through quantitative calculations is 1189.288 hm² more than the actual area of cropland fallow (2900 hm²) in 2018. Considering the allocation of fallow urgency and fallow area, the fallow land would be mainly distributed in the southern part (2 towns, 9 villages) of Quzhou County, rather than current scatter spatial distribution (8 towns, 17 villages). This re-search can provide methods and ideas for accurately formulating the cropland fallow program, more research perspectives (society, economy and ecology) are suggested to considered and be integrated for making the fallow program of multi-objective synergy in future research work.”

 

I suggest an improvement of the manuscript before acceptance.

Answers：Thanks for your agreement.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The authors have improved the manuscript and can be accepted for publication