2.1. Literature Review
Regarding the evaluation of green growth, two approaches have been developed. One way is to measure it by a single indicator, such as energy intensity or carbon intensity [
12,
13], which only considers pollution emissions but not the inputs or growth in the economy. The other is through green total factor productivity (GTFP), which is mainly analyzed by the data envelopment analysis (DEA) method; this is widely used by scholars in the fields of business, education, and information management for efficiency measurement in various fields [
14,
15,
16]. This method was first proposed by Charnes, et al. [
17], and can include multiple input and output variables and does not require a specific form of the production function. However, bias may be introduced due to this method’s radial and angular selection. Tone [
18] constructed a standard efficiency model of SBM with slack variables on this basis, which effectively overcomes this problem but cannot be distinguished when there are multiple decision effective units [
19]. For this reason, Tone [
20] further proposed the SBM super-efficiency model, but this model fails to consider non-desired outputs. Later, Tone [
21] optimized it again by including non-desired outputs in the SBM super-efficiency model to incorporate environmental factors well into the efficiency measure. In addition, scholars have continuously improved the existing DEA models. Afsharian, et al. [
22] applied the generalized DEA model to make the original implicit assumptions of DEA, including the linear cost and benefit functions, explicit to overcome the respective input/output factor problems related to factor selection, dual-role factors, and undesirable factors. Mosbah, et al. [
23] proposed a DEA model for input/output decomposition. Due to the reality of inputs/outputs and the different levels of information of managers, managing resources through (global) efficiency scores can be limiting; therefore, decomposing these into the efficiency of input/output components will be effective in improving resource management decisions. In summary, scholars have provided excellent ideas for optimizing the DEA model. The GTFP calculated by DEA is also more comprehensive and accurate than a single indicator, which is now widely used in the industry. With people’s increasing attention on the agricultural ecological environment, some scholars have also begun to apply it to the agricultural field. For example, Chen, et al. [
24] used this model to calculate China’s agricultural sector’s green total factor productivity. Shi, et al. [
25] used this model to calculate the utilization efficiency of agricultural water resources in the Yangtze River Basin of China.
Regarding the factors influencing green growth, studies have shown that FDI, imports, and exports influence green growth. FDI will promote industrial agglomeration, generate competitive effects and promote economic growth, and increase regional pollution [
26]. Imports may lead to pollution reduction in the importing country. However, exports are likely to lead to an increase in “pollution paradise”, which is still detrimental to environmental protection overall [
27]. Thus, due to the negative externality characteristics of environmental pollution, regulating the harmonization of economic and environmental development through market-oriented factors often leads to “market failure”, and environmental regulation is one of the most direct and effective measures to solve this problem [
28,
29]. Rubashkina, et al. [
30] studied manufacturing industries in 17 European countries and concluded that government spending on reducing environmental pollution positively impacts technological innovation but is not significant for TFP growth. Wang and Shao [
31], based on data from Group 20 countries, and using the environmental policy stringency index provided by the OECD to characterize formal environmental regulation, concluded that the effect of formal environmental regulation on GTFP shows a positive contribution only at high levels, while both technology and education levels, which are informal environmental regulations, have a positive effect on GTFP. In agriculture, there is a lack of comprehensive discussion on environmental supervision at present. Ma and Tan [
32] chose the number of environmental protection-related policies as a proxy variable for environmental regulation and concluded that it is beneficial for increasing GTFP in agriculture, while Xu and Yin [
33] chose environmental investment in agriculture as a proxy for environmental regulation and concluded that it is detrimental to GTFP in agriculture. Huang, et al. [
34] further refined the industry, using the chemical fertilizer price as a proxy variable, and found an inverted U-shaped relationship between it and the wheat GTFP.
Among the mechanisms by which environmental regulation affects green growth, technological innovation is a research hotspot. Acemoglu, et al. [
35] introduced endogenous and directional technological changes into the growth model with environmental constraints and concluded that appropriate environmental regulation would trigger technological innovation. Franco and Marin [
36] found that environmental regulation in downstream industries is an important driver of innovation and productivity in the industry, based on data from 13 manufacturing sectors in eight European countries. Li and Shi [
37] took Chinese manufacturing and new energy enterprises as the research objects, respectively, and concluded that environmental regulation would stimulate technological innovation. However, fewer articles have examined the mechanisms of technological innovation as environmental regulation in the field of agriculture.
In conclusion, the available studies help understand the relationship between environmental regulation and green growth. However, the findings vary widely and are not generalizable due to the different ways of measuring heterogeneous environmental regulations. Moreover, there are few articles related to environmental regulation and green growth in the agricultural sector, and the research on agricultural technological innovation as the mechanism of environmental regulation is also rare. As the fruit tree with the largest planting area in China, citrus has a rapid increase in yield, while efficiency and environmental problems cannot be ignored. However, the current research on green growth of the citrus industry is still relatively weak. This paper has the following marginal contributions: (1) Chemical fertilizer and pesticide losses and carbon emissions were included as non-desired outputs in measuring citrus green total factor productivity to more objectively and comprehensively reflect the green development changes in China’s citrus industry. (2) Integrating heterogeneous environmental regulation, technological innovation, and green growth into the same framework, the impact of heterogeneous environmental regulations can be reflected more comprehensively and realistically, and the mechanism of technological innovation’s role in them can be verified. (3) The citrus industry, a highly market-oriented industry, was selected as the research object to more significantly optimize the resource allocation efficiency of the agricultural market.
2.2. Theoretical Mechanism
Because environmental regulations are more diverse and their effects vary significantly, scholars usually discuss environmental regulations in categories, mainly command-and-control, market-incentive, and guide-participatory [
38]. Command-and-control environmental regulation mainly includes environmental protection-related laws, regulations, and rules, restraining farmers’ production behavior through mandatory regulations. It is the primary way of environmental regulation in the agricultural sector in China [
39]. Market-incentive environmental regulation regulates production behavior through market-based instruments such as environmental taxes and fees and environmental investments, while agricultural production in China is now free of sewage charges and environmental taxes (except for large-scale livestock and poultry farming), so environmental investments are the main application of market-incentive regulation in Chinese agriculture. There is no unified definition of informal environmental regulation regarding guidance and participation, which mainly includes environmental protection news and publicity, environmental protection-related internet search indexes, environmental protection proposals of the National People’s Congress and the Chinese People’s Political Consultative Conference, and environmental protection petitions. Under the unique production conditions in rural areas, it is difficult to objectively reflect the impact of participatory environmental regulations such as Internet search indexes and proposal petitions in the agricultural industry due to the low quality of farmers and poor information channels [
40], while the guidance-based regulation represented by environmental news publicity is a more effective measure of informal environmental regulation in the agricultural sector [
41]. In summary, this study classifies environmental regulations into command-and-control environmental regulations (CER), market-incentive environmental regulations (MER), and guidance-based environmental regulations (GER), and analyzes the mechanism of action of different types of environmental regulation in turn.
CER refers to mandatory constraints such as laws, regulations, rules, and regulations related to environmental protection. By formulating agricultural non-point source pollution control policies, such as chemical fertilizer and pesticide registration systems and delimiting prohibited and restricted breeding areas, local governments control various pollution sources such as chemical fertilizer and pesticide, inhibit the emission of some pollutants from the source, indirectly restrict the entry of producers below the threshold efficiency, and squeeze out inefficient incumbent producers [
42], to promote environmentally friendly production. However, the public choice theory states that governments at all levels are “rational economic people” in the political market [
43] and that principal–agent problems may exist between central and local governments [
44]. Moreover, as local governments make GDP growth their primary objective [
45], there is a competition between “incomplete implementation” and “race to the bottom” of written legislation [
46,
47]. Moreover, due to the concealment, dispersion, and randomness of agricultural non-point surface pollution, the enforcement and supervision of agricultural and environmental pollution are difficult. In addition, the quality of farmers and rural infrastructure construction level is low, the information asymmetry phenomenon is prominent, laws and regulations and administrative penalties to deter the effect of guidance are limited, and the effectiveness of CER may be compromised.
MER mainly refers to market-based regulatory instruments such as fiscal spending on environmental protection. For example, the government compensates farmers for green production behaviors using “promoting governance with rewards” and “substituting rewards for subsidies”, promoting the utilization of agricultural waste as a resource and the use of ecological agricultural materials, or using financial funds to build environmental protection infrastructure such as rural roads, farmland water, and production services to reduce the production cost of agriculture and increase the profit. However, due to the typical externalities of environmental regulation results, the phenomenon of “free riders” has become the norm [
48]. The increase in environmental protection investment has shared the cost of environmental pollution for farmers, making them less responsible for environmental pollution and squeezing out their motivation and resources for environmentally friendly production, thus inhibiting the green growth of the citrus industry. Therefore, there may be both positive and negative effects of MER on agricultural production, and the magnitude of both effects varies with the intensity of MER, which in turn has a nonlinear effect.
GER refers to the means of enhancing public awareness of environmental protection such as environmental news and publicity. Mainly through environmental information disclosure, a more transparent information environment is built to effectively maintain citizens’ rights to environmental information, participation, and supervision, while providing the public as well as producers with more environmental value judgments and cognitive guidance [
49], effectively bringing into play the informal institutional binding force of social opinion [
50]. Signaling theory suggests that the media’s promotion of positive environmental messages can strengthen public awareness of environmental protection, weaken strategic interactions between subjects, align the environmental goals of producers with those of governments at all levels, and guide producers to choose more environmentally friendly production methods and restrain governments from “imperfect enforcement” [
42]. The negative environmental information propaganda will damage the reputation image of the exposed producer and have a deterrent effect on other producers in power, and the social pressure brought by this will guide producers to environmental production. Initially, there will be an increase in environmental production costs, but as environmental regulations strengthen, producers become more environmentally conscious and take the initiative to optimize resource allocation and improve environmental protection, compensating for the increased costs and increasing green total factor productivity. Therefore, GER may have positive or negative effects on the aforementioned environmental regulations and vary with the intensity of GER, eventually producing a U-shaped or inverted u-shaped nonlinear effect. On this basis, Hypothesis 1 is proposed.
Hypothesis 1. There is a non-linear relationship between heterogeneous environmental regulations and citrus green growth.
From a static perspective, the neoclassical view is that environmental regulation has a “compliance cost” effect, leading to increased operating costs and thus crowding out R&D investment, which discourages technological innovation and reduces productivity and competitiveness, a view mainly represented by Jaffe [
51] and supported by subsequent studies by many scholars [
52,
53]. In contrast, a series of scholars, represented by Porter [
54], analyze the issue from a dynamic perspective and believe that environmental regulation with reasonable design can produce an “innovation compensation” effect. It forces producers to innovate, reduce production costs, and improve production quality [
35,
55]. In the agricultural field, increased environmental regulations will encourage farmers to use green farming materials or adopt green production methods, which will bring “compliance costs” to farmers, making them increase production costs or reduce business returns, squeezing out inputs for technology and management, and indirectly inhibiting green growth. However, there may also be incentives for farmers to adopt chemical fertilizer and pesticide reduction, efficiency technologies, and agricultural waste recycling technologies for profit maximization, resulting in an “innovation compensation” effect; this will optimize factor allocation and reduce pollution emissions through technological improvements, which is conducive to green growth (
Figure 1). Furthermore, technological innovation promotes green growth by improving the utilization rate of agricultural factors and reducing agricultural non-point source pollution [
56]. In summary, technological innovation is essential for environmental regulation to play a role. Based on this, Hypothesis 2 is formulated.
Hypothesis 2. Technology innovation plays an intermediary role in the process of environmental regulation affecting the green growth of citrus.