1. Introduction
Food security is essential for ensuring there is a basic guarantee to meet human food demand and is also an important foundation for global sustainable development [
1]. Under the coordination of the United Nations, countries around the world have jointly taken the most effective action in history to eradicate poverty and hunger, achieving significant results [
2,
3]. However, in reality, food issues remain a focus of international attention. Although the incidence of food shortages in developing countries has decreased from 23.3% in 1990 to 8.3% in 2015, there are still 265 million people suffering from severe hunger globally, indicating that the issue of food insecurity remains severe [
4,
5]. In recent years, factors such as extreme weather and the Ukraine crisis have further worsened the food security situation, and the continuous growth of the global population has brought ever greater pressure on the provision of food for all humanity [
6,
7].
On a global scale, with the continuous advancement of urbanization and industrialization, there have been drastic changes in the utilization pattern of cropland, which has had a significant impact on food security [
8]. On the one hand, to meet the demand for construction land due to urban development, a large amount of cropland has been converted into construction land [
9]. On the other hand, due to further increased profitability of other agricultural production activities, as well as the continuous increase in input costs and labor costs for grain production, an increasing number of farmers are withdrawing from grain production [
10,
11], leading to the emergence of non-grain production on cropland (NGPCL). NGPCL primarily refers to all activities conducted on cropland that do not involve the production of grain. This includes planting cash crops, as well as engaging in agricultural activities such as aquaculture, animal husbandry, and fallowing of cropland [
12,
13,
14]. Although NGPCL does not cause explicit loss of cropland quantity, it implicitly reduces the grain output capacity of cropland, posing a serious threat to regional food security [
15]. Influenced by factors such as urbanization and dietary structure upgrades among residents, NGPCL in China is becoming increasingly common [
16]. As China contributes approximately 50% of the grain output in Asia, and its share of grain imports in global grain trade is close to 30% [
10,
17], China serves as a crucial node in world grain trade [
18,
19]. Therefore, the phenomenon of NGPCL in China has attracted widespread attention from the international community.
In 2019, the area of cropland used for non-grain production in China accounted for 29.06% of the total cropland area [
20], and by 2021 this figure had increased to 33.2% [
21]. NGPCL is more prevalent in the southern and eastern regions of China. In the southwest region, due to significant loss from the agricultural labor force, there is frequent fallowing of cropland in mountainous areas, and a large amount of cropland is also used for planting economic forests. According to statistics, 42.87% of cropland in Chongqing Municipality is not used for planting grain [
7,
12]. In the southeast region, due to the rising cost of labor in the labor market and the increasing demand for cash crops, the main crops have shifted from grains to vegetables and other oil crops. More than 40% of cropland resources have been used for non-grain production [
22,
23]. From 2015 to 2021, China’s annual average sown area of grain crops decreased by 0.4%, with the planting area of rice and wheat decreasing by 8629 km
2 and 9985 km
2, respectively [
24]. Although the improvement in grain production efficiency in China has compensated for the impact of the decrease in grain production area on grain output, breakthroughs in production technology are inevitably facing bottlenecks. The compression of grain production space caused by NGPCL will pose a serious threat to domestic grain output and affect global food supply [
25].
Although importing food can alleviate the pressure on regional food production, from a global perspective, the total amount of cropland resources is limited. Extensive NGPCL on a large scale is bound to increase the pressure on the global food supply. Considering the serious impact of NGPCL, there has been a gradual increase in research on this topic. Currently, there is no clear academic concept for NGPCL. Foreign scholars typically approach a related analysis from the perspective of agricultural sustainable development, discussing the theoretical logic and specific practices of diversified planting [
26,
27,
28]. Chinese scholars were among the first to regard NGPCL as an independent utilization method for cropland, and they have conducted discussions around the spatial characteristics and influencing factors of NGPCL. Scholars commonly measure the level of NGPCL within research units based on indicators such as the proportion of cropland area planted with cash crops or the proportion of cropland area planted with cash crops amid transferred cropland [
22,
29]. Moreover, scholars often use administrative regions as research units and employ geographical analysis models, such as spatial autocorrelation and standard deviation ellipses, to explore the spatial patterns of NGPCL [
30,
31,
32]. Research indicates that hilly and mountainous areas are prominent regions for NGPCL, and cropland in economically developed areas is more likely to be used for non-grain production [
33,
34]. Cropland near urban areas is generally not cultivated for grain crops [
14]. In terms of the influencing factors of NGPCL, scholars commonly utilize social statistical data for analysis. It is generally believed that the quality of resources is a direct influencing factor of NGPCL [
35,
36], and the production cost triggered by urbanization is the core influencing factor [
37,
38]. Additionally, farmers’ planting preferences can also affect the occurrence of NGPCL [
39,
40]. NGPCL also produces various effects: it compresses the space for grain production, which increases the pressure on the regional food supply [
41]. Research has also indicated that large-scale NGPCL can have negative impacts on the ecological environment, such as soil hardening and water pollution [
42,
43]. However, some scholars point out that reasonable NGPCL is a specific practice of sustainable agricultural systems. It can help enhance the region’s water resources’ carrying capacity and ecological benefits [
44] and, further, meet the diversified dietary needs of residents [
45].
The existing research has provided significant references for the scientific understanding of NGPCL, but there are still some limitations. Firstly, many existing studies rely on the cropland area planted with cash crops as an indirect indicator for the analysis. This research paradigm is one-sided, failing to elucidate the theoretical basis of NGPCL and overlooking its various types. Secondly, land parcels are the fundamental units of cropland utilization, yet most existing studies use administrative regions as research units, relying on social statistical data and lacking related analyses based on a parcel-level perspective. This makes it difficult to reveal the characteristics of NGPCL from a micro perspective. Thirdly, the analysis of relevant influencing factors mostly focuses on socio-economic development and farmer preferences, with fewer scholars analyzing the impact of differences in parcel characteristics on NGPCL from a “cost–revenue” perspective. Fourthly, existing research mainly focuses on economically developed regions, but the risk of NGPCL is relatively higher in mountainous areas due to poorer agricultural production environments [
46]. Lechang City is a typical representative of underdeveloped mountainous areas. In recent years, with the continuous advancement of urbanization, a severe loss of agricultural labor has occurred, and the trend of NGPCL in Lechang City has become increasingly apparent. Conducting relevant analysis in Lechang City will help deepen our understanding of the characteristics and driving mechanisms of NGPCL in mountainous areas, providing a case foundation for the formulation of food security policies.
Therefore, this study takes Lechang City as the research area, constructs the definition criteria and measurement index for NGPCL, analyzes the clustering characteristics, typological features, and distribution characteristics of NGPCL at the parcel level, and further explores the driving mechanisms of NGPCL based on the “cost–revenue” perspective. Finally, corresponding policy recommendations are provided based on the research findings. These research results can provide a source of reference for the sustainable utilization of cropland and the control of food security in China and also contribute to a deeper understanding of NGPCL in mountainous areas by global scholars.
5. Discussions
5.1. Research Discussion
This study presents three main innovations. Firstly, it clarifies the evolution logic of NGPCL based on the theory of land marginalization. It further reveals the multi-type nature of NGPCL and introduces its innovative measurement index. Secondly, unlike traditional studies, this research combines land survey data to conduct relevant analyses of NGPCL at the plot level. This approach effectively reveals the characteristics of NGPCL from a micro perspective. The conclusions drawn from such research provide more realistic evidence for the government to effectively manage cropland utilization. Thirdly, previous studies on the influencing factors of NGPCL have mostly focused on socio-economic variables, paying less attention to the impact of plot characteristics on cropland utilization. This study adopts a “cost–revenue” perspective to select relevant influencing variables and combines statistical models to conduct analysis, effectively filling the gaps in related research.
By comparing the conclusions of this study with existing findings, an attempt is made to validate the reliability of the conclusions drawn in this research. This study reveals varying degrees of non-grain production across different types of cropland, which is akin to the characteristics of cropland marginalization [
55,
56]. Due to the favorable irrigation conditions in paddy fields and the suitability of plains for mechanized production [
57,
58], paddy fields and plains exhibit lower levels of marginalization and are less prone to NGPCL.
Regarding the distribution characteristics of NGPCL, Chen found a clear terrain preference for NGPCL in basic farmland [
59]. Additionally, similar distribution characteristics of cropland abandonment in mountainous areas were also observed [
60]. The conclusions of these scholars are consistent with the findings of this study, indicating that the extent of NGPCL varies with changes in terrain and location conditions. This study also found that NGPCL exhibits significant clustering characteristics, with terraces having a lower degree of clustering compared to slope cropland. This phenomenon may firstly be attributed to the large-scale abandonment of poor-quality slope cropland in mountainous areas [
61]. Secondly, because marginal terraces have lower economic benefits and higher production costs, they are more prone to NGPCL [
62].
In terms of the factors influencing NGPCL, due to differences in regional climate conditions and farming practices, the elevation in the study area has a negative impact on NGPCL. This conclusion differs from the marginalization mechanism of cropland in the southwestern mountainous areas [
63], indicating the complexity and regional differences in the formation mechanism of NGPCL. Therefore, the management and governance of NGPCL should be tailored to local conditions, and corresponding strategies should be implemented accordingly.
At the same time, it is worth noting that the availability and quality of data often determine the reliability of research conclusions. The land survey data used in the study are obtained through a nationwide unified survey by national-level agencies, ensuring high reliability. The remaining data also come from official scientific research institutions, effectively guaranteeing data quality. The above data are also commonly used in related studies [
14,
64]. Therefore, high-quality research data can also confirm the reliability of the conclusions of this study.
The article clarifies the theoretical basis of NGPCL, innovates the measurement index for NGPCL, and reveals the multi-type characteristics and driving mechanisms of NGPCL. However, this study focuses on the influence of plot characteristics on farmers’ operational choices and lacks relevant discussion on policy factors. In fact, national policy constraints and administrative incentives have significant impacts on agricultural production decisions. Future research will pay more attention to the relationship between regional policies and NGPCL, while establishing studies on NGPCL from different scale perspectives, and attempt to analyze the characteristics and formation mechanisms of NGPCL from multiple angles.
5.2. Recommendations for Countermeasures
In response to the findings of this study, this research proposes the following policy recommendations with the aim of providing guidance for the management of NGPCL and the sustainable utilization of cropland in mountainous areas.
- (1)
Optimize cropland irrigation facilities to enhance the quality of cropland
Research indicates that different types of cropland exhibit varying levels of non-grain production. Therefore, efforts should be made to optimize water storage facilities and improve the layout of ditches and canals. Simultaneously, irrigation facilities should be further improved to mitigate the impact of natural precipitation on grain production. There should also be a strong push for the transformation of slope cropland to prevent the concentration of large-scale abandonment of low-quality slope cropland. Additionally, attention should be paid to the effects of natural factors such as heavy rainfall. It is essential to actively optimize the maintenance and supervision mechanisms of terraces to prevent field collapse caused by heavy rainfall and subsequent loss of grain yield. In summary, efforts should be focused on enhancing the overall quality of cropland resources and increasing farmers’ income from grain production.
- (2)
Promote mechanized production suitable for the local conditions to enhance the efficiency of grain cultivation
Research shows that topographical and locational conditions are key factors constraining the input of mechanical elements. Therefore, on one hand, measures such as leveling field surfaces and consolidating field plots should be taken to optimize the mechanized environment of cropland. On the other hand, it is necessary to further improve transportation networks and widen roads for machinery access to mountainous areas. This can effectively reduce commuting and transportation costs for farmers. Additionally, conventional large-scale machinery cannot be used in mountainous and hilly regions. Therefore, there should be a strong push to introduce multifunctional small-scale agricultural equipment. Environmental improvement and the introduction of suitable machinery can effectively address the marginalization of grain production in mountainous areas, thereby increasing farmers’ income from grain production.
- (3)
Improving the agricultural production structure promotes the sustainable development of cropland in mountainous areas.
Reasonable NGPCL not only enhances the stability of agricultural systems but also increases farmers’ income. Therefore, further improvements should be made to the agricultural production structure. Firstly, with the aim of ensuring food security, grain production areas should be designated based on the actual situation of cropland resources in each region, ensuring sufficient grain output. Secondly, local governments should aim to revitalize cropland resources and allow unused cropland in other areas to be utilized for alternative agricultural activities. Measures such as agricultural subsidies should be implemented to encourage farmers to develop idle cropland resources. For instance, in mountainous areas where there is a large-scale abandonment of inferior slope cropland, the government could permit farmers to plant economic trees on these slopes and provide technical or financial support. This approach not only prevents the idle use of cropland resources but also increases farmers’ income sources. However, it is worth noting that all agricultural production and development must follow the premise of protecting cropland resources. The local government should actively fulfil its supervisory role and reasonably restrain the extent and intensity of cropland development by farmers.