1. Introduction
As a major agricultural country, China has made significant progress in agricultural development in recent years. According to the Ministry of Agriculture and Rural Development, China’s total trade in agricultural products in 2006 amounted to
$63.48 billion and has shown a rising trend in the past 16 years, reaching a figure of
$334.32 billion in 2022 [
1]. However, as the scale of China’s agricultural trade continues to expand, it is increasingly becoming a source of serious environmental problems, among which agricultural surface pollution has been identified as an important factor hindering the sustainable development of the country’s agricultural production. Moreover, these pollutants can also damage the soil structure, cause fires, and pollute the air environment which in turn have an impact on health. According to China’s seventh population census, 40% of all cancers occur in rural areas, where the resident population is only half that of towns and cities. At present, the relevant authorities and measures implemented to tackle agricultural surface pollution in China are characterized by decentralization, uncertainty, and delay [
2]. Indeed, it is difficult to identify the main body responsible for the management of agricultural pollution and supervision of the process of governance, thereby resulting in insufficient participation by the main body and an unsatisfactory governance effect. Currently, the prevention and control of agricultural surface pollution in China is far from satisfactory. For a prolonged period of time, the Yangtze River Economic Zone—considered the most important agricultural production base in China—has been a region of rapid economic growth. However, the degree of agricultural surface pollution is concomitantly increasing, which is severely restricting the sustainable economic development and ecological protection of this economic zone. Accordingly, as a key area of concern for the green development of agriculture in this new environmentally aware era, in this study, we selected panel data for the Yangtze River Economic Belt for empirical analysis [
3].
Given that the agricultural environment has the attributes of public goods, governments should in theory be the main governing bodies addressing the problem of agricultural surface pollution, and the environmental regulations these governments adopt largely influence whether the problem of agricultural surface pollution can be effectively solved [
4]. As far as the market is concerned, failure of the input factor market exacerbates the use of inferior products by farmers to a certain extent, thereby contributing further to agricultural surface pollution. In the context of China’s large national population, the pressure of market demand for agricultural security, and small-scale agricultural operations, farmers comprise the largest number of agricultural producers with the largest total production and operation area and are consequently considered the major source of agricultural surface pollution [
5].
Our group—in the book “Research on Lake Protection Strategies in Northern Jiangsu” [
6]—selected farmers in Jinhu County, Huai’an City, Jiangsu Province, China as the survey object, resulting in 240 questionnaires being distributed, 238 recovered—excluding duplicates and incomplete invalid questionnaires—and 162 used as valid questionnaires; the questionnaire validity rate was 68%. The results of the questionnaire showed that 8% of the farmers chose to rely very much on fertilizers, 33% chose to rely generally on fertilizers, 24% chose to rely on fertilizers, 19% chose to rely slightly on fertilizers, and 16% chose not to rely on fertilizers during planting, which indicates that farmers in the region still rely on fertilizers to a high degree at this stage to obtain high output and high yields. According to the Ministry of Agriculture and Rural Affairs of the People’s Republic of China [
7], chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) have been identified as the main pollution load indicators of agricultural non-point source pollution. Existing literature [
8,
9] analyzed the main sources of agricultural non-point source pollution through clustering analysis and concluded that the main sources of agricultural non-point source pollutants TN and TP in China consist of livestock and poultry manure and farmland cultivation. Although the pollution situation varies from province to province, these two pollutants combined account for the majority of the pollution, exceeding 90%.
Researchers in both China and other countries have expended considerable effort in assessing the problem of agricultural surface pollution and the factors contributing to this pollution from several different perspectives. From a governmental perspective, studies have shown that an improvement in the intensity of government environmental management is conducive to an improvement in its efficacy [
10]. Similar studies have also confirmed that the development of appropriate environmental regulations is an important strategy for curbing agricultural surface pollution [
11,
12,
13]. For example, to effectively reduce the degree of agricultural surface pollution, governments can use agricultural insurance as an important policy tool to promote the green transformation of agricultural practices [
14]. Environmental regulatory policies can also promote advances in agricultural production technology; for example, via the implementation of environmental regulatory policies that tax firms that pollute beyond prescribed limits. This approach accordingly aims to incentivize firms to adopt innovative technological approaches, thereby enhancing their environmental performance and competitiveness, and consequently reducing the degree of agricultural surface source pollution [
15]. From a market perspective, the studies conducted to date have mainly focused on analyzing input factor markets. With progress in the development of agricultural technology, there has been an increase in the input of agricultural production factors within the market, which has brought about larger-scale agricultural production and exacerbated the problem of agricultural surface pollution [
16]. Furthermore, from the perspectives of the chemical fertilizer market and agricultural labor force, several scholars have assessed the impact of fertilizer market distortion and reductions in the rural labor force on the application of chemical fertilizers by farmers, and, ultimately, the exacerbation of agricultural surface pollution [
17,
18,
19].
Based on the foregoing considerations, in this study, where we focus on the Yangtze River Economic Belt, we developed an econometric model to examine the spatial and temporal characteristics and contributory factors of agricultural surface pollution from the multiple perspectives of government, market, and farmers. The main contributions and innovations of this study are as follows. Firstly, we focus on the Yangtze River Economic Belt in China, rather than on a specific province or city, and assess the current status of agricultural surface pollution in the region to provide policy recommendations for the realization of sustainable economic and ecological development. Secondly, we examine the impacts of environmental regulations, factor market distortion, and labor transfer on agricultural surface pollution from the perspectives of the government, market, and farmers, which provides new insights into this problem. Thirdly, to provide targeted suggestions for the promotion of pollution management and realization of rural revitalization, we employed spatial Durbin and threshold effect models to examine the spatial spillover effect of factor market distortion. This means that factor prices no longer truly reflect the effects of the scarcity of factor resources and the value of products on agricultural surface pollution and its threshold effect on this pollution under different intensities of environmental regulation. Fourthly, considering the time lag and negative externalities of environmental pollution, we evaluated the robustness of our analysis using a dynamic GMM method, which takes into account the effects of the lagged term, thereby correcting this error and enabling us to present more credible conclusions.
4. Conclusions and Recommendations
In this study, we demonstrated that there is a positive spatial correlation between agricultural surface pollution in the Yangtze River Economic Belt and an obvious homogeneous spillover effect. Our analysis of the contributory factors revealed that an increase in the distortion of input factor markets will promote a significant increase in agricultural surface pollution within the Yangtze River Economic Zone, whereas increases in governmental environmental regulation and the numbers of rural laborers migrating from the country to urban areas will significantly reduce the agricultural surface pollution in this region. Further research indicated that factor market distortion has a significant single-threshold effect on the effects of environmental regulation on agricultural surface pollution and that this effect is characterized by a non-linear pattern of an initial increase and subsequent decline.
Based on our findings in this study, we propose the following policy recommendations.
Firstly, from the perspective of the coordinated regional development of the Yangtze River Economic Belt, given the tendency of spatial agglomeration of agricultural surface pollution, the mutual influence between different provinces and municipalities has become an important factor in determining the level of regional agricultural surface pollution. Provincial and municipal governments in the Yangtze River Economic Belt region should accordingly strengthen the linkage and establish a sound system of common governance, not only to formulate feasible governance programs in their provinces and municipalities according to local conditions, but also to take into consideration the governance links with their neighboring provinces and the municipalities therein. In particular, the western provinces and municipalities, which tend to be characterized by the highest levels of pollution in the economic zone, should break away from the original “who pollutes, who governs” mode and examine their common governance systems. The government can also refer to the legal enactment framework in the United States, i.e., through the central government, to issue a general overview of the general direction, and each local government to enact locally adapted laws and policies according to the environmental pollution situation in each place.
Secondly, when governments formulate environmental regulations, they can appropriately increase the strength of regulations and continuously improve their applicability and feasibility. Moreover, attention should be paid to environmental regulations and other policies to coordinate operations, such as market mechanisms that match the degree of perfection, thereby enabling the identification of the maximum extent of agricultural pollution that can alleviate the degree of surface pollution of the “first threshold value”. In addition, to implement ecological compensation incentives, governments should not only balance rewards, such as in the simultaneous formulation of punitive laws and regulations, but also continue to improve the agricultural ecological protection compensation system in the system-level design of ecological compensation mechanisms, fertilizer reduction, soil transformation, and the use of green production technology by farmers.
Thirdly, the effective supervision of all aspects of the production and marketing of green agricultural products can be achieved by constructing a model of co-management and co-regulation between the state and society. Taking the fertilizer factor market as an example, governments could promote a balance between supply and demand in the fertilizer market by limiting the minimum or maximum price of fertilizers and granting tax incentives or subsidies, thereby reducing the circulation of low-quality fertilizers and the intensity of fertilizer application to a certain extent.
Fourthly, manpower is an effective guarantee for promoting rural revitalization. If a country wishes to strengthen and promote agriculture, it should focus on cultivating talent. Accordingly, local governments should implement policies designed to attract and cultivate high-quality farmers. In addition, in terms of policy, governments should optimize rural policies, thereby providing incentives for urban migrant workers and unemployed college students to return to their hometowns to start their businesses. Similarly, in terms of education, relevant programs should be developed to cultivate agricultural professionals, whilst promoting the teaching of the concept of sustainable agricultural development. In terms of industry, the resources of the Internet should be exploited to achieve the development of industrial wisdom, promote the progress of human resources, and create a cultured skilled workforce with a good theoretical and practical understanding of the treatment of pollution. The “three farmers” team.
Finally, our study only examined the factors affecting agricultural surface pollution in the Yangtze River Economic Zone and did not examine the effects of agricultural surface pollution on other factors such as regional economic development, ecological environment, water quality, and groundwater. Meanwhile, for the specific content of agricultural surface pollution, only its main components, including total Tn, Tp, and Cod, were studied, ignoring some very trace but difficult-to-handle heavy metals, including boron, potassium, and selenium, which enter the soil through fertilizers and pesticides, and need to be solved through the control of fertilizers and remediation [
43]. In the future, we plan to broaden our research to cover these aforementioned areas.