In October, 2021, the National Development and Reform Commission and other departments issued the "14th Five-Year Plan" to promote cleaner production in agriculture. In 2023, the No.1 Document of the Central Committee proposed to speed up the popularization and application of the technology of reducing and increasing the efficiency of agricultural inputs, promote the integration of water and fertilizer, and establish and improve the collection, utilization and treatment system of agricultural wastes such as straw, agricultural film, pesticide packaging waste and livestock manure. In this issue, experts are invited to discuss related issues.
Take the road of intensive agricultural development to protect the ecological environment
What is the significance of promoting agricultural cleaner production to save resources and protect the environment?
Yin Changbin (researcher, Institute of Agricultural Resources and Agricultural Regionalization, China Academy of Agricultural Sciences, chief scientist of agricultural resources utilization and regionalization team): Agricultural cleaner production refers to practical agricultural technology and scientific agricultural production management mode that can not only meet the needs of agricultural production, but also rationally utilize resources and protect the environment. Its essence is to improve agricultural production technology through the production and scientific use of environmentally friendly green agricultural chemicals in the whole process of agricultural production, reduce the adverse effects of agricultural production on the environment and human beings, and make full use of by-products in agricultural production. Agricultural cleaner production is a high-efficiency production mode, which can not only prevent agricultural pollution, but also reduce production costs, produce safe agricultural products and realize the resource utilization of some by-products.
"People’s Republic of China (PRC) Cleaner Production Promotion Law" points out that "agricultural producers should scientifically use chemical fertilizers, pesticides, agricultural films and feed additives, improve planting and breeding techniques, realize high-quality and harmless agricultural products and recycle agricultural production wastes, and prevent agricultural environmental pollution. It is forbidden to use toxic and hazardous wastes as fertilizers or for land reclamation. " It can be seen that agricultural cleaner production mainly includes two fields of agricultural production, planting and aquaculture, and its process control includes three links: pre-production, mid-production and postpartum.
According to the characteristics of China’s agricultural development and resources and environment, to achieve sustainable agricultural development, we must abandon the extensive agricultural production mode with high energy consumption, heavy pollution, low efficiency, monotonous structure and single product, promote agricultural clean production, and take the road of intensive agricultural development with upgrading technology, improving economic benefits, saving resource consumption and protecting ecological environment.
Implementing agricultural cleaner production is the need to promote the sustainable utilization of agricultural resources. The serious shortage and waste of agricultural water and soil resources is the primary factor restricting China’s agricultural development. China is extremely short of water resources, and most of the farmland is located in arid and semi-arid areas. In addition, the unreasonable irrigation methods in traditional agriculture lead to the low efficiency of water resources utilization. According to China Water Resources Bulletin in 2021, the effective utilization coefficient of farmland irrigation water in China is only 0.568. Cultivated land resources are increasingly scarce, and the quality of cultivated land is generally low. According to the results of the third national land survey, the cultivated land area in China was 1.918 billion mu at the end of 2019, 113 million mu less than that in 2009, and the per capita cultivated land in China was less than 0.1 hectare. The problem of the balance of cultivated land occupation and compensation occurs frequently all over the country. In 2020, 704,700 mu of cultivated land was occupied by illegal construction. At the same time, the area of superior land and higher land in cultivated land is less, and the deterioration of some quality factors of cultivated land and the quality of cultivated land in some areas is prominent. Agricultural cleaner production can save and regenerate resources, improve the efficiency of resource utilization, reduce the input of materials and energy, and make rational use of limited water and soil resources by adjusting and optimizing the agricultural production structure.
Implementing agricultural cleaner production is the need to prevent and control agricultural production pollution. Traditional agricultural production relies too much on the input of modern chemical synthetic substances, which not only brings development to farmers’ income and social economy, but also poses a great threat to the sustainable development of man and nature, resulting in more serious resources and environmental problems. Agricultural pollution has become an important factor restricting the development of agricultural economy. Chemical fertilizer pollution, straw pollution and livestock manure pollution have seriously damaged the agricultural ecological environment. The application of chemical fertilizers in China increased from 9 million tons in 1978 to 52 million tons in 2021. The application intensity of chemical fertilizer per hectare increased from 273.5 kg in 2002 to 308.2 kg in 2021, but the efficiency of chemical fertilizer application is still at a low level, showing the characteristics of high input and medium output. In 2019, the output of livestock manure, crop straw and agricultural film was 3.05 billion tons, 870 million tons and 2.465 million tons respectively. It can be seen that in recent years, although China has made some achievements in the pollution control of agricultural production, the agricultural pollution problem is still grim because of the large base of chemical fertilizer consumption and organic waste production. Agricultural cleaner production requires reducing the use of chemical fertilizers, using green pesticides, recycling agricultural wastes, reducing the harm to the environment and human beings, and realizing the unity of social, ecological and economic benefits.
In 2011, the Opinions on Accelerating Agricultural Cleaner Production pointed out that the sense of responsibility and urgency for promoting agricultural cleaner production should be further enhanced, and clear requirements were made from three aspects: pre-production, mid-production and post-production, namely, strengthening the prevention of pollution sources in agricultural production areas, promoting the cleanliness of agricultural production processes, and strengthening the control of agricultural non-point source pollution, and the governance and supervision framework of agricultural cleaner production gradually became perfect.
In December 2016, the State Council issued the Comprehensive Work Plan for Energy Conservation and Emission Reduction in the Thirteenth Five-Year Plan, put forward the main objectives of agricultural cleaner production by 2020, determined the development direction of agricultural cleaner production, began to establish and improve the market-oriented mechanism of agricultural cleaner production, and further refined and improved the work requirements and plans of agricultural cleaner production.
In October 2021, the National Development and Reform Commission and other departments issued the "National Cleaner Production Implementation Plan for the 14th Five-Year Plan", and set the goal of cleaner production in agriculture by 2025, that is, 60 million mu of high-efficiency water-saving irrigation area will be added, the recovery rate of waste agricultural films will reach 85%, the comprehensive utilization rate of straw will be stable at over 86%, and the comprehensive utilization rate of livestock manure will reach over 80%. The improvement direction of efficient and clean agricultural production mode is put forward from five aspects: water-saving irrigation, chemical fertilizer reduction and substitution, pesticide reduction and efficiency increase, comprehensive utilization of straw and agricultural film recycling treatment, which promotes the formation of a number of typical cases that can be popularized and replicated, and provides a reference technical model for realizing agricultural clean production.
The reduction of agricultural inputs has achieved results
In recent years, what progress has China made in promoting the reduction of agricultural inputs and increasing efficiency?
Shi Rongguang (researcher, Institute of Environmental Protection Research and Monitoring, Ministry of Agriculture and Rural Affairs): Agricultural inputs refer to substances used or added in the production of agricultural products. Including seeds, seedlings, fertilizers, pesticides, veterinary drugs, feeds and feed additives, and agricultural engineering materials such as agricultural films, agricultural machinery, agricultural engineering facilities and equipment. Excessive and improper use of agricultural inputs has caused serious ecological and environmental problems and triggered a series of social problems such as food safety and human health, which has become an important factor restricting the sustainable development of agriculture and rural areas in China.
Heavy metal pollution in soil. Compared with industrial and mineral pollution sources, agricultural inputs have the characteristics of large quantity, wide coverage, strong concealment and continuous use. In recent years, the abuse and improper use of agricultural inputs such as chemical fertilizer, organic fertilizer, pesticide, agricultural film and sludge in China have aggravated soil heavy metal pollution. For example, the formula feed used in livestock and poultry breeding often contains a certain proportion of additives that can promote growth and improve feed utilization rate, but some of them are absorbed by livestock and poultry, and are often excreted in the form of livestock manure, which is directly applied to farmland or processed into organic fertilizer, thus leading to the accumulation of heavy metals in soil. The heat stabilizer used in agricultural film production contains heavy metals such as cadmium and lead, which may cause heavy metal pollution in soil in the process of using plastic greenhouses and plastic films in large quantities.
Soil organic matter and microplastics pollution. The application of agricultural inputs will cause the pollution of new pollutants such as persistent organic pollutants and microplastics in the environment. Relevant research shows that sewage irrigation is one of the main ways for microplastics to enter the farmland ecosystem, and the synthetic microfiber produced in the laundry process is one of the sources of microplastics in the farmland ecosystem.
Agricultural non-point source pollution. Agricultural non-point source pollution comes from a wide range, mainly from planting and aquaculture. The average amount of chemical fertilizer per mu of crops in China is higher than that in major countries in the world, especially in orchards and protected vegetables.
Air pollution. Fertilization in farmland is an important means to increase soil nutrients and increase the output of agricultural products. However, only part of the fertilizer applied to farmland enters the soil and is absorbed by crops, and a considerable part of the fertilizer volatilizes into the atmospheric environment, thus causing pollution.
Ecological environment destruction. Excessive use of agricultural inputs such as chemical fertilizers, pesticides and agricultural films will also destroy the ecological environment and reduce biodiversity. Membrane fragments that are not easy to recycle accumulate in the soil, which hinders the water infiltration between soil layers and reduces the water absorption capacity, which is one of the reasons for soil salinization. In addition, various additives in the production process, such as fertilizers, veterinary drugs, agricultural films and plastic films, will also be released into the soil during use, which will pollute the ecological environment with the infiltration and migration of soil moisture, and there is also the risk of enrichment and transfer to agricultural products and livestock.
In November 2022, the Ministry of Agriculture and Rural Affairs issued the Action Plan for Reduction of Chemical Fertilizer by 2025 and the Action Plan for Reduction of Chemical Pesticides by 2025, demanding that scientific fertilization and application be continuously promoted, and that chemical fertilizers and pesticides be reduced and increased, so as to provide more powerful support for ensuring food security and green and high-quality development. All localities have further promoted the implementation of zero growth in the use of chemical fertilizers and pesticides, the concept of scientific fertilization and application has been continuously strengthened, technology has been continuously innovated, measures have been continuously implemented, and the reduction of agricultural inputs has achieved positive results.
First, the consumption of chemical fertilizers and pesticides has been declining continuously. Promote soil testing and formula fertilization on a larger scale and at a higher level, speed up the replacement of chemical fertilizers with organic fertilizers, and promote the application of new fertilizers such as microbial fertilizers. The application of agricultural chemical fertilizers and pesticides has been declining for six consecutive years. In 2021, the application of agricultural chemical fertilizers in China was 51.91 million tons, a decrease of 13.8% compared with 2015. In 2021, the use of pesticides was 248,000 tons, a decrease of 16.8% compared with 2015.
Second, the structure of fertilization and application is more optimized. Formulate the quota amount of nitrogen fertilizer for rice, wheat, corn, rape and other crops, and issue scientific fertilization technical opinions for crops at different agricultural times to guide scientific fertilizer selection and use. The application ratio of nitrogen, phosphorus and potassium was adjusted from 1∶0.53∶0.36 in 2015 to 1∶0.49∶0.42 in 2021. The effect of controlling phosphorus and increasing potassium was obvious, and the compound rate was further improved. The structure of pesticide varieties has been continuously optimized, and the proportion of low-toxic and micro-toxic pesticides registered in China is over 85%. The market share of new varieties with high activity and environmental protection has increased year by year.
Third, fertilization and application methods have been continuously improved. Popularization and application of high-efficiency fertilization technology, the coverage rate of soil testing and formula fertilization technology remained above 90%, and formula fertilizer accounted for more than 60% of the total fertilization of rice, wheat and corn, and blind fertilization and excessive fertilization phenomenon were basically curbed. In 2021, the coverage rate of green prevention and control of major crop pests and diseases reached 46%, an increase of 23 percentage points over 2015; The coverage rate of major crop diseases and insect pests control reached 42.4%, an increase of 9.4 percentage points over 2015.
Fourth, the utilization rate of chemical fertilizers and pesticides has improved significantly. We will implement a number of key projects and popularize a number of scientific fertilization and application modes. In 2021, the utilization rate of chemical fertilizers in China’s three major grain crops will reach over 40%, an increase of 5 percentage points over 2015, and the utilization rate of pesticides will reach 40.6%, an increase of 4 percentage points over 2015.
In addition, a number of major scientific research projects have been implemented, and the input reduction technology has been developed and popularized. Based on China’s current strategic demand of reducing fertilizer and pesticide application and increasing efficiency, in 2016, the Ministry of Science and Technology set up the key project of "Research and Development of Comprehensive Technology for Reducing Fertilizer and Pesticide Application and Increasing Efficiency" among the first batch of national key science and technology projects, and set up 49 related projects, with the national funding of 2.397 billion yuan. The theory, method and technical system of efficient utilization of chemical fertilizers and pesticides are constructed through the research on the mechanism and limit standard of efficient utilization of chemical fertilizers and pesticides, the technological innovation and equipment research and development of fertilizers and pesticides, and the research on the integration and demonstration application of technologies for reducing fertilizer and pesticides and increasing efficiency.
Combining planting and breeding to realize internal circulation of agricultural resources
How to improve the cleanliness level of agricultural production process and form an efficient and clean agricultural production model?
He Ke (Special Researcher of Agricultural Green and Low-carbon Development Laboratory of Huazhong Agricultural University): In order to ensure food security, agricultural product quality safety and ecological environment safety, the cleanliness of agricultural production process is highly valued. The "14th Five-Year Plan" National Cleaner Production Implementation Plan clearly requires improving the cleanliness level of agricultural production process. Clean agricultural production process refers to the application of new technologies, new materials, new processes, new equipment and facilities and new management measures with the characteristics of high resource utilization efficiency, eco-environmental friendliness and remarkable economic benefits to agricultural production process.
From the perspective of planting industry, the key point of cleaning production process is to reduce the pollution caused by unreasonable use of inputs by deepening soil testing and formula fertilization, popularizing lateral deep fertilization of rice, controlling the production and use of highly toxic and residual pesticides, advocating ecological control, and developing high-strength recyclable plastic film and degradable agricultural film. From the point of view of livestock and poultry breeding, the focus of clean production process is to develop and popularize healthy breeding technology, ensure the reduction of the use of veterinary antibacterial drugs, and continuously promote the source reduction and comprehensive utilization of livestock and poultry breeding waste. For example, research and development and promotion of water-saving and material-saving clean farming technology, source reduction technologies such as dry cleaning manure and microbial fermentation, and advanced and applicable comprehensive utilization technologies of livestock and poultry breeding wastes such as heterotopic fermentation bed, manure padding reuse and sewage fertilizer utilization. From the perspective of aquaculture, the focus of cleaning the production process is to increase the popularization and application of safe and efficient artificial compound feed, factory recycling aquaculture, water quality control technology and environmental protection equipment.
China attaches great importance to the cleanness of agricultural production process, and passed the "People’s Republic of China (PRC) Cleaner Production Promotion Law" as early as 2002, which provided a legal basis for the development of agricultural cleaner production. In 2011, the Opinions on Accelerating Cleaner Production in Agriculture was issued, which further stipulated the specific work requirements for cleaning the agricultural production process. In 2015, the Ministry of Agriculture’s Implementation Opinions on Fighting Hard the Prevention and Control of Agricultural Non-point Source Pollution put forward the principle of "one control, two reductions and three basics" for the specific problem of agricultural non-point source pollution control. Driven by these laws and policy documents, China has achieved fruitful results in the development of clean agricultural production process. According to the data released in "Bulletin on the Ecological Environment in China in 2021", the comprehensive utilization rate of livestock manure in China in 2021 has exceeded 76%, the comprehensive utilization rate of straw has reached over 87%, and the recovery rate of waste agricultural films has also stabilized at over 80%. At the same time, according to the statistics of the National Agricultural Technology Center, in 2022, the application area of green prevention and control of crop pests and diseases in China was as high as 1.184 billion mu, and the coverage rate of green prevention and control reached more than 50%.
It is an important means to promote the cleaning of agricultural production process to actively develop circular agriculture with planting and breeding. China has always attached importance to the combination of "planting" and "raising". As early as the Song Dynasty, there appeared the simple concept of low-carbon circular development, such as "one after another to generate and use each other". During the Ming and Qing dynasties, there appeared some modes of combination of planting and breeding in Taihu Lake, such as "rice-fish symbiosis" and "mulberry pond". Nowadays, the connotation of the combination of planting and breeding is further enriched, and it is considered as a green and low-carbon agricultural model, which takes the manure produced by livestock and poultry breeding as the fertilizer source of planting, and realizes the transformation of matter and energy between animals and plants through planting. Specifically, this agricultural model takes "green and low-carbon production" and "recycling" as important means, and changes the traditional linear growth economic system that relies on agricultural resource consumption into an economic system that relies on green and low-carbon agricultural resource recycling, so that the whole process of resource utilization realizes the step-by-step and closed-loop use of material and energy, improves the efficiency of resource utilization, and helps to enhance agricultural economic and ecological benefits. On the one hand, the combination of planting and breeding system can reduce the production cost and improve the economic benefit through material recycling and reuse. Some scholars have pointed out that the comprehensive planting and breeding model of rice fields can increase the benefits by 1,500 yuan to 2,000 yuan per mu. On the other hand, the main characteristics of the combination of planting and breeding are low exploitation, high utilization and low emission, which can realize the resource circulation within agriculture, make livestock manure replace chemical fertilizer, and make crop waste such as straw into feed for aquaculture, thus reducing pollution.
Strengthen the resource utilization of agricultural waste.
What are the typical practices at home and abroad to turn agricultural waste into treasure?
Li Ji (Professor, School of Resources and Environment, China Agricultural University): The resource utilization of agricultural wastes is the inherent requirement of building an agricultural power. In recent years, China’s agricultural green development has made important progress, and the use of chemical fertilizers and pesticides has decreased year after year, but the pollution and treatment of agricultural wastes are still in the initial stage. China is the country that produces the most agricultural wastes in the world. According to incomplete statistics, in 2019, the output of agricultural waste in the world was about 20.3 billion tons, including 16 billion tons of livestock manure and 4.3 billion tons of straw. In the same period, the output of agricultural waste in China was about 3.9 billion tons, including 3.05 billion tons of livestock manure and 870 million tons of straw. However, due to the low technical level and low comprehensive utilization rate, the environmental pollution is serious.
According to the National Agricultural Sustainable Development Plan (2015-2030) and the requirements of relevant departments, the overall goal of resource utilization of agricultural waste is: by 2030, the crop straw in the main agricultural producing areas will be fully utilized, the comprehensive utilization rate of aquaculture waste will reach more than 90%, and the livestock manure in large-scale farms will be basically utilized, so as to achieve ecological consumption or discharge up to standard. In order to achieve the above goals, it is necessary to strengthen the technological innovation and application of agricultural waste resource utilization, so that organic nutrients from soil can return to the land and truly realize material circulation.
As early as the 12th century, Zhu Xi, a famous scholar in the Southern Song Dynasty, wrote in the article "Don’t abandon yourself" that "manure is filthy, and if it is applied to the fields, the grain will depend on it to show its reality", and put forward the view that "there is nothing to abandon in heaven", which is the bud of China’s waste resource utilization thought. The concept of resource utilization of agricultural wastes abroad gradually became popular in 1970s, which provided many experiences for other countries. Japan has promoted "Biomass Town", a demonstration project combining rural wastes with the development of eco-agriculture, and used the wastes from breeding industry for fertilizer and energy production. Rape, rice, wheat and other crops are produced in Aidong Town, Shiga Prefecture, Japan. The waste from rape production and processing is used as raw materials, part of which is used to produce high-quality feed or fertilizer, develop livestock and poultry breeding and ecological agriculture, and part of which is converted into biofuel as agricultural machinery fuel, realizing the organic integration of planting, breeding and energy production. Because of the good climate and soil conditions in Europe and other countries, the planting and breeding circular agriculture model is mainly implemented. Danish farms are equipped with livestock farms and farmland. Livestock farms mainly raise sows and cows, while farmland mainly grows barley crops. The scale of farming is strictly in accordance with the principle of planting and breeding balance, and the livestock density is kept at 1.1 livestock units per hectare, and the utilization rate of agricultural waste resources reaches 90%. The United States has a high level of agricultural modernization and mechanization, and implements a conservation tillage model. Most corn stalks are directly left in the fields through ploughing. Ohio is one of the important agricultural states in the United States, with conservation tillage accounting for about 45%.Among them, about 70% of soybeans adopt no-tillage, 30% of corn adopt less tillage, and the area adopting continuous no-tillage can reduce fuel consumption and emissions by 35%.
At present, the comprehensive utilization rate of livestock manure in China is over 76%, and the matching rate of manure treatment facilities in large-scale farms is over 90%. The manure treatment facilities are basically available, but most farms still mainly use simple methods such as manure composting and manure storage. According to the investigation, the treatment method of livestock manure in China is mainly fertilizer utilization. At present, there is a general disconnect between planting and breeding in China’s aquaculture industry, and there is a lack of supporting farmland around the farm, which leads to the lack of timely replenishment of soil nutrients in cultivated land, and agricultural production has always been in a state of operation in which planting exceeds breeding and output exceeds input. In 2021, the utilization rate of straw in China reached 88.1%, and the utilization rates of fertilizer, feed, fuel, base material and raw material were 60%, 18%, 8.5%, 0.7% and 0.9% respectively, of which the amount of straw returned to the field reached 400 million tons. Although returning straw to the field has good economic and social benefits, there are still some practical problems to be solved urgently, such as the straw returning to the field is not easy to rot, which affects the sowing quality of the next crop. Therefore, the utilization efficiency and technical level of agricultural waste resources in China need to be further improved.
Anaerobic digestion is one of the treatment methods of agricultural waste energy, which is widely used to produce biomass fuel. Shandong Minhe Bio-company treated the manure with low water content as fertilizer and the manure with high water content as biogas energy, and established a resource utilization system of organic "fertilizer+biogas+biogas fertilizer" to realize the efficient resource output of livestock manure. The company has 3.7 million sets of parents’ meat breeders, with an annual output of 160,000 tons of organic water-soluble fertilizer and 50,000 tons of solid bio-organic fertilizer. The waste treatment mode of "decentralized collection of manure-centralized treatment of biogas-biogas thermal power generation-biogas fertilizer market sales" is adopted to produce biogas power generation from agricultural organic wastes through anaerobic fermentation, with a daily treatment of 1,000 tons of chicken manure and 800 tons of sewage and a daily production of 100,000 cubic meters of biogas. Biogas generates more than 20 million kilowatt hours a year, purifies 15 million cubic meters of bio-gas, concentrates biogas slurry to produce 13,140 tons of organic water-soluble fertilizer, and can reuse 96,360 tons of water during purification. The resource products are used in organic ecological planting bases, realizing the harmless treatment and resource reuse of agricultural waste resources.
Aerobic composting is an effective way to fertilize agricultural wastes. Guangxi Jinsui is a leading agricultural enterprise integrating banana, sugarcane and cassava planting, processing and sales. The domestic land circulation is 87,000 mu, and the annual output of ecological organic fertilizer is 100,000 tons. The tank aerobic fermentation process is used to treat agricultural wastes, and 32 fermentation tanks are equipped, with an average daily processing capacity of about 600 tons. The main raw materials of agricultural wastes are plant-based raw materials such as filter mud, sugarcane pulp, bean dregs and cassava. After four steps of raw material pretreatment, primary fermentation, aging and post-processing, high value-added bio-organic fertilizer is produced, which is applied to 50,000 mu of banana planting, which fundamentally solves the outlet problem of filter mud and other wastes and meets the demand of agricultural planting bases for organic fertilizer.
Straw returning to the field is a measure to improve soil fertility and increase production, which is widely paid attention to in the world today. It can not only eliminate the air pollution caused by straw burning, but also increase fertilizer and increase production. After 38 years of crushing wheat and corn stalks and returning them directly to the field for cultivation, the contents of soil organic matter, available nitrogen, available phosphorus and available potassium and the yield of wheat and corn increased significantly, indicating that straw returning to the field is an effective measure to improve cultivated land fertility, which can not only improve soil fertility and soil nutrients, but also improve soil structure, reduce soil bulk density, increase soil permeability, break soil hardening, improve soil moisture conservation and increase crop drought resistance.
The application of the above model should comply with the principle of adapting to local conditions and treat agricultural wastes in combination with actual production in order to maximize economic and ecological benefits. Participants in agricultural waste recycling include industrial management departments, professional associations, technology extension departments and farmers, agriculture-related enterprises, scientific research institutions, etc. It is necessary to fully cooperate, innovate practices, establish a mature system, and continuously promote the efficient operation of agricultural waste recycling system.
