After the introduction of plastic film mulching technology into China, it has effectively improved the water resource utilization rate and grain production capacity in arid and semi-arid areas, promoted the increase of crop yields and farmers' income in these areas, and played an important role in ensuring national food security. The huge economic benefits have been hailed as the 'white revolution'. However, with the increase in usage and the expansion of the scope of use, the problem of residual film pollution in farmland has become more and more serious, becoming a 'white pollution' in rural areas. Main source.
At present, what is the overall use of mulch film in China? What effect has it played in agricultural production? What is the current status and hazard of mulch film residue? How to proceed with the prevention and control of mulch pollution and recycling? Recently, the reporter interviewed relevant experts around the above issues. .
Annual use of 1.45 million tons, covering 12% of cultivated land
The film mulching technique was invented by Japanese scientists in the 1950s and introduced to China in the late 1970s. According to Chen Xuegeng, a researcher at the Chinese Academy of Engineering, the Xinjiang Academy of Agricultural Sciences, “In the 1980s, the Shiheziyu District, the eighth division of the Xinjiang Production and Construction Corps, was introduced. The film mulching technology has quickly realized the mechanization of plastic film mulching. At present, the crops planted by Xinjiang and Xinjiang Corps have been expanded from cotton to tomato, corn, sugar beet, pepper, melon, etc., with a total area of more than 5,000 mu. Great economic benefits. '
In China's arid and semi-arid regions, the total amount of water resources is insufficient, and the spatial and temporal distribution of precipitation is uneven. More than 60% of the precipitation is concentrated in 7, 8 and 3 months. There is less precipitation in winter and spring, and the frequency of spring drought is high and the damage is high. National Agricultural Technology Liu Tianjin, director of the Promotion Service Center, believes that the mulching film covering technology has achieved autumn rain and spring use, which can effectively alleviate the impact of spring drought on agricultural production and increase the grain production capacity of natural precipitation. 'Northern China's corn planting is mainly distributed over 450 mm of rainfall. , areas below 1800 meters above sea level. By promoting the film mulching technology, the corn planting range has been expanded to more than 300 mm of rainfall, below 2,350 meters above sea level.
Yan Changrong, a researcher at the Institute of Agricultural Environment and Sustainable Development of the Chinese Academy of Agricultural Sciences, believes that mulching covers the long-term lack of water constraints in agricultural production in arid regions, improving resource utilization efficiency and getting rid of the passive situation of drought resistance. The corn planting area moved 2~5 latitudes northward, and the yield increased by 30%~50%. Through statistical analysis of the results of field control experiments of 2644 pairs (film covered and uncoated) of 756 test sites nationwide, the film cover was covered. It can significantly improve crop yield and water use efficiency. ' In addition, mulching can maintain a good soil structure, inhibit soil salinity, prevent disease from spreading with water, inhibit weeds and pests, and save pesticides, fertilizers, irrigation water and labor. The investment can increase the temperature and ensure the planting and growth period of fruits and vegetables, achieve anti-seasonal production, improve canopy illumination, and improve the quality of fruits and vegetables.
According to the National Bureau of Statistics, in 2015, China's mulching film coverage reached 275 million mu, and the amount of use reached 1.455 million tons. It is predicted that by 2024, China's mulch cover area will reach 330 million mu, and the use will exceed 2 million tons. Yan Changrong said with anxiety, 'This means that more than 12% of the cultivated land in China uses mulch every year. In Xinjiang, where cotton production accounts for 70% of the country, all cotton fields use mulch, and 93% of the country's flue-cured fields use mulch. The crop varieties of mulch are constantly developing from vegetables to cash crops and even to large-scale food crops.'
'White Revolution' has spawned 'white pollution'
The use of such a large-scale film has both advantages and disadvantages. On the one hand, it has played a huge role in improving the quality of agriculture, but on the other hand it has caused serious damage to the soil environment, resulting in the 'white revolution' resulting in 'white pollution'. Negative product.
Yan Changrong said: 'Ordinary polyethylene film (PE film) is a polymer compound, which is difficult to decompose or degrade under natural conditions. With the increase of years of use and the ineffectiveness of residual film recovery measures, the accumulation of residual film in soil is increasing. More, local areas have formed serious residual pollution, leading to a series of production and environmental problems, such as: destroying soil structure, affecting crop growth and farming operations, resulting in crop yield reduction, increased labor input, and waste of resources. 'Liu Tianjin also said that 'At present, China's mulch residue problem is outstanding. According to the typical survey, the average film residue in the northwest loess and drought area is 7 kg/mu, and the serious area is over 15 kg/mu. The mulch residue destroys the soil structure, affects the water and fertilizer migration, crop emergence and growth. Development, reducing crop yields and quality of agricultural products.'
The results of a study showed that when the amount of film residue in the soil reached 120 kg per hectare, the yield of wheat, corn and cotton would decrease by 17.8%, 13.2% and 16% respectively. Currently, due to the continuous promotion of machine-made cotton, the film Entry into cotton has become an important factor affecting the quality of cotton, which will lead to difficulties in printing and dyeing of cotton, and the rate of commodities is reduced. In addition, many crop straws are important livestock feeds, such as peanut straw is a very high quality feed, but in recent years, Shandong, After planting peanuts in some parts of Northeast China, the problem of intertwined mulch in peanut stalks is very prominent. As long as it is mulch peanuts, ordinary people are afraid to use their straw as feed.
In Europe and Japan, which use the same large area of mulch film, there is no 'white pollution' problem. Yan Changrong explained: 'In addition to Japanese and European laws, polyethylene film must be recycled and treated according to industrial waste, and their mulch film is more. It is a high cost between 0.018 and 0.03 mm thick, high-strength mulch film, easy to recycle. In China, the ultra-thin film is used between 0.005 and 0.01 mm, which is difficult to recycle or degradable.
In fact, the national standard promulgated in 1992 stipulated that the thickness of the mulch film was 0.008±0.003 mm. However, in actual production and application, in order to reduce the cost, the 0.005 mm thick mulch film became the mainstream product in the Chinese market. October 2017 The newly revised mandatory national standard "Polyethylene Blowing Agricultural Floor Covering Film" was released. Compared with the 1992 version of the standard, the change mainly manifests as 'three improvement and one mark', which improves the film thickness, mechanical properties, weather resistance. And the obvious position on the product certificate is marked 'Recycling after use, reduce environmental pollution'. In particular, it is clearly stated that the film thickness should not be less than 0.01 mm, and the new national standard has been officially implemented since May 1, 2018. The mulch film is no longer allowed to be produced and sold. Experts say that the new national standard is to use good mulch film to solve the problem of mulch residue and reduce 'white pollution'. It provides strong technical support and legal guarantee, which is conducive to filming machine operation and recycling. use.
'Because the residual film is difficult to recycle and the labor intensity is high, many farmers turn the residual film directly into the ground. The damage accumulated to the soil and crops can not be underestimated. 'Worried, Chen Xuegeng also believes that there is no suitable residual film recycling. Machinery is also one of the reasons for the 'white pollution' becoming more and more fierce. 'In fact, China has been developing residual film recycling machinery since the 1980s. More than 100 kinds of machinery have emerged, but there are not many requirements that can really meet the requirements.
Promote alternative technologies, degradable membranes, and gradually reduce mechanical recovery
In May 2017, the Ministry of Agriculture issued a notice on the “Agricultural Membrane Recovery Action Plan” to strengthen the management of agricultural film pollution and improve the utilization level of waste agricultural film resources. It is proposed that by 2020, the national agricultural film recycling network will be continuously improved and the utilization level of resources will be utilized. Continuous improvement, the recycling rate of agricultural film has reached more than 80%, 'white pollution' has been effectively prevented and controlled. Then, how to control the pollution of plastic film? Increase the recycling rate, experts also talked about their own views.
Liu Tianjin proposed, 'Insist on reduction, increase efficiency, substitution, degradation, cycle five measures, and do a good job of residual film treatment. Carry out the evaluation of suitability of plastic film mulching technology, scientific planning, reasonable reduction of some mulch corn planting, adjustment of planting structure. Dryland agricultural technology innovation, integrated film replacement technology, straw cover, grass cover, water retention agent, drought resistance and anti-reverse preparation, rainwater supplement irrigation, water and fertilizer integration and other technologies to replace the film cover, achieve film reduction, control from the source Residual film damage. '
In this regard, Chen Xuegeng suggested that in the application of mulch film reduction in farmland, the benefits of film planting production are not very obvious, and the growth period can meet the requirements of crop maturity. It is recommended not to use mulching film cultivation. Yan Changrong also proposed to minimize film mulching. Degree, to prevent the abuse of mulching film, advocate a multi-purpose film, reduce the coverage ratio, reduce the amount of film injection, 'select a film with moderate thickness, good toughness and strong anti-aging ability, basically no damage after the first use, the second time It can be directly drilled and no-tillage on the above, to reduce the film injection and tillage, to save time, labor and environmental protection. For example, in Enshi, Hubei, first, the film is covered with flue-cured tobacco, and the tobacco leaves are planted on the original mulch after harvest. Cabbage, radish, etc.; after harvesting of covered corn in Gansu, Gansu, the second planting of rapeseed, wheat, etc.
Experts believe that the promotion of biodegradable mulch film is an important way to solve the problem of residual film pollution in the future. Although China has made great progress in the research and development of degradable film in recent years, Yan Changrong also frankly said that the price of degradable film is much higher. Moreover, there is a big difference between the temperature and the temperature of the ordinary polyethylene film, and the tensile strength is not enough to meet the requirements of the agricultural machine film. 'Need to further strengthen the research on the degradation of the film in raw materials, formula, process and technology, improve Product quality and reduce product cost. In addition, according to different crops and regions, choose a reasonable degradable film, and support appropriate agronomic techniques and application models to promote the application of degradable film. 'Yan Changrong said.
Chen Xuegeng said: 'Degradable film instead of polyethylene film is the ultimate trend, but polyethylene film is still the mainstream in the next 10 to 15 years, and there is a long period of coexistence between the two. It is necessary to completely recycle the new film and residue in the layer. Gradually recovering the mulch film is placed in the same important position, no new account is owed, and the old account is gradually reduced. The residual film content in the soil will gradually decrease, and the mechanized recycling of the residual film is an inevitable measure. 'He believes that the advanced and applicable residual film recycling machine It should meet 5 standards: It is easy to operate, no complicated adjustment is needed for the machine, and the driver can work normally after simple adjustment; high working efficiency and high reliability; residual film recovery rate can reach more than 90%, recycling The operating cost is not more than 20 yuan/mu; with automatic film rolling function, the recovered residual film roll can be conveniently stacked; the residual film residual rate after recycling is low, creating basic conditions for resource utilization. Since 2015, Chen Xuegeng's team has developed 16 kinds of residual film recycling machines and obtained a number of invention patents. In the field operation demonstration last October, the residual film recovery rate of some machines can reach 80%~90%, which makes China's machinery recycling membrane A good place to start. 'Next, I intend to further improve these plastic film recycling machine, for the year 2020 entered the practical stage. Truly for' white pollution 'effective governance, but also a pure land in agricultural production.'
Chen Xuegeng finally suggested that 'the state should formulate corresponding policies and regulations as soon as possible, and gradually use laws and regulations to restrict the use and recycling of mulch film to form rules. Establish the principle of 'who uses who recycles', and strictly stipulate the residual film recovery rate of newly-coated mulch film in the same year. If the standard of recycling is not met, it will be punished by economic means. If the standard of recycling is reached, the reward and subsidy will be clearly given. ' He finally said: 'Residual film recycling is a worldwide problem. It is estimated that by 2020, China will have new improvement. If the increase is not increased, the stock will gradually decrease. '