How to Solve the Soil Crisis? The New Agricultural Subsidy Policy Comes to the Rescue
News from the recently held Fifth China Environmental Remediation Development Strategy Forum reveals that the draft of the "Soil Pollution Prevention and Control Law," drafted by the Environment and Resources Protection Committee of the National People's Congress, has officially been released for public comment. According to the plan, the proposed version of the law will be submitted to the Standing Committee of the National People's Congress for review next year and will be incorporated into the legislative plan.
At present, among the "three major battles" of air, water and soil pollution prevention and control in China, only the legislation on soil pollution prevention and control is missing. For many years, there have been no legal norms for soil pollution prevention and control, owing both to the problem of weak "economic measures" at the practical level and to disagreements related to specific remediation measures. All of this reflects the complexity and difficulty of soil pollution prevention and control work.
China has a large population and little land, and the issue of food production remains prominent. A person engaged in the grain trade in Guangzhou once asked me for help: the rice she sold directly to customers, which had good sales, was actually complained about for exceeding the cadmium standard. How should such soil be remediated? Through testing some soil samples she collected, I found that the total cadmium content in the soil was only 0.2 mg/kg, below the limit of China's current soil environmental quality standard (0.3 mg/kg). However, because the soil pH was low, less than 5.0, the cadmium in her rice exceeded the standard by more than 1 fold. Since then, I have encountered many such cases one after another. Some farmers and organic farmers are full of confusion: on farmland far from pollution sources, how could the rice they work so hard to grow exceed the cadmium standard?
The emergence of this strange phenomenon is undoubtedly related to the tremendous impact that the excessive application of fertilizers and pesticides in China has brought to the soil ecosystem. The main harm caused by the overuse of chemical fertilizers and pesticides is the sharp acidification of soil and the weakening or even loss of soil ecosystem functions. According to the research results published by Zhang Fusuo and others in Science in 2010, since the 1980s, over the past 30 years, the pH of China's soil has dropped by 0.13 to 0.80 units, with the greatest decline in agricultural ecosystems. A drop of 0.80 units means that soil acidity has increased by as much as 6 fold.
As the article points out, if this magnitude were to be achieved by nature, it would take tens of thousands of years. This shows how great the impact of massive fertilizer application is on soil properties and soil ecological functions. In some heavily fertilized regions such as the Yangtze River Delta and the Pearl River Delta, the impact is even more severe.
Soil, as a product formed under the action of the five major soil-forming factors of parent material, climate, organisms, topography and time, is an ecosystem with highly vigorous life. The number of organisms in a handful of soil is greater than the population of the Earth. In 1 sq m of soil, in principle there should be 10 trillion bacteria, 3,000 earthworms, flatworms and 1 vertebrate, etc. However, under conditions of high fertilizer and high pesticide use, visible organisms have been almost completely lost, and invisible organisms have also been deeply affected. Normal biological functions of soil such as nitrogen fixation, phosphate solubilization and potassium solubilization cannot be performed. In addition, due to the destruction of the soil food web chain, some soil organisms become "dominant alone," causing crop health problems such as root rot and root-knot nematode disease.
Soil acidification directly leads to the release of heavy metals originally present in minerals in the soil, the activation of heavy metals adsorbed on soil clay particles, and the inability of soil to "age" exogenous heavy metals. These processes lead to an increase in the availability of heavy metals in soil, and food production exceeds standards. Especially for cadmium, a harmful heavy metal that easily migrates in the soil-plant system, the cadmium activation effect of soil acidification is even more obvious, resulting in the production of food exceeding standards even though China has established the world's strictest soil environmental quality standard.
The "Reform Plan for Establishing a Green and Ecological-Oriented Agricultural Subsidy System," adopted on November 1, proposes highlighting the green and ecological orientation, accelerating the implementation of related agricultural subsidy policy reforms, and shifting the policy objective from primarily increasing quantity to placing equal emphasis on quantity, quality and ecology. Establishing a green and ecological-oriented agricultural subsidy system reform plan undoubtedly injects corrective driving force into agricultural production trapped in a vicious cycle, and is also a very good institutional guide for restoring unhealthy soil damaged by the excessive application of chemical fertilizers and pesticides.
China's comprehensive agricultural subsidies began in 2004, mainly in chemical fertilizers, agricultural machinery and basic farmland construction. These subsidies undoubtedly played an important role in ensuring steady increases in grain production and achieving China's "twelve consecutive years of increase" in grain output. But these measures also promoted the excessive application of chemical fertilizers and pesticides, resulting in the current situation in which China uses less than 10% of the world's land while applying 1/3 of the world's fertilizer; the average amount of chemical fertilizer applied reaches 463 kg per hectare, 3.5 times the world average application amount of 131 kg per hectare, and also 1.93 times the commonly regarded warning line of 225 kg per hectare.
Among the many soil-forming factors, the added human factors in agricultural soil have become the strongest influencing factor. It can be said that human factors (fertilization and pesticide application) have greatly changed soil biological factors in a short period of time, leading to unhealthy soil. Therefore, it can be confidently believed that establishing a green and ecological-oriented agricultural subsidy system reform plan will help soil health.
(The author Chen Nengchang is a researcher at the Guangdong Institute of Eco-environmental Science and Technology)