After chemical fertilizers, pesticides and herbicides, the "white pollution" caused by plastic film residues is becoming another major social hazard of non-point source pollution in China.

In some parts of Xinjiang and Gansu, the accumulated accumulated waste plastic film is as high as 20 kg per mu, equivalent to 5 layers of plastic film in the land. The residue of soil film has reduced the yield of crops by 10% to 20%, and the effect of the film mulching technology is decreasing, and the "white revolution" in the past is turning into a "white pollution".

To curb residual pollution of plastic film and accelerate the treatment of white pollution has become an urgent problem.

Extensive promotion

The application of agricultural film in China began in the 50s of last century, and was initially used only in small arch shed for rice seedling raising. At the end of the 70s, some scientific research institutions began to use waste plastic film instead of other materials for ground coverage test.

In 1979, China introduced a plastic film mulching cultivation technology from Japan to organize scientific research cooperation and joint experiments nationwide. By 2008, China's investment in plastic film reached 1 billion 78 million kg, an increase of 4 times compared to 1991. The area of plastic film mulching reached 15 million 613 thousand hectares, an increase of 133 times than that in 1982.

Yan Rongchang, a researcher at the Institute of agricultural environment and sustainable development of Chinese Academy of Agricultural Sciences, introduced that in Xinjiang cotton area, because of insufficient accumulated temperature, some High-yielding Cotton Varieties could not complete the growth period. By using film mulching technology, the demand for the temperature of cotton growth was well solved.

"Xinjiang has become the most important cotton producing area in China, and the technology of plastic film mulching is indispensable." In an interview with the Chinese science newspaper, he said that it was through this technology that the production and efficiency of crops in the cold and southwestern mountainous areas in the north of China were increased, and the yield of Maize in the northwest was at least 30%.

Concern about sustainability

The problem of soil pollution caused by such large-scale application of plastic film is gradually emerging. The poor degradation of the agricultural film material, the difficulty of recovery, the poor benefit of reuse, and the imperfect relevant policies and regulations, have aggravated the pollution degree and the difficulty of the treatment of agricultural film in our country.

"Now this problem has reached a very serious level. In some areas, we can not continue normal agricultural production without governance." Yan Rongchang stressed.

"Film mulching is not an irreplaceable technology, but a good technology at present, especially in Gansu, where the annual precipitation is below 400 millimeters, so that its corn production has been greatly improved." Shan Lun, academician of the Chinese Academy of engineering, said in an interview with the China Science Daily.

The technology of plastic film mulching has made outstanding contributions to China's grain production, and its sustainability has not been given due attention for a long time.

Yan Rongchang believes that this sustainability is mainly reflected in the adaptability of film mulching technology, because not all places are suitable for the application of this technology; in addition, the effects of large area mulching on regional ecosystems, especially water cycles, will result in regional soil dryness. Some questions remain to be studied.

"I visited Japan. Japan is the birthplace of plastic film mulching technology. They are used only in specific crops (such as tobacco plants) and in specific areas." Said the lolen.

"In terms of remediation of contaminated soil, it is rather difficult to repair soil contaminated by plastic film." Shan Lun stressed that what should be done at present is to protect the existing cultivated land environment.

Environmental film needs to be supported by policy

The residual pollution of plastic film is becoming more and more serious, which is closely related to the thinning and poor recycling of plastic film produced in China. Weng Yunxuan, the Secretary General of China Plastic Association biodegradable plastics (Specialized Committee), said that in order to save the cost, some enterprises have made the film 0.004 mm or 0.005 millimeter, nearly half lower than the national standard. The thinner the plastic film is, the easier it is to break in the soil, which brings difficulties to recycling and aggravates the degree of soil pollution.

At the same time, as a effective way to solve the problem of "white pollution", biodegradable plastic film is facing the bottleneck of market application because of its high cost.

Chen Xuesi, a researcher at the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, is undertaking a project of research and development of biodegradable plastic film funded by the National Natural Science Foundation of China. He believes that the technical problems of plastic film and other technical problems are not very different at home and abroad, and the most important problem is price. "The cost of biodegradable plastic film abroad may be 3~5 times the cost of ordinary film. Although domestic products are not so expensive, they are more than twice as much as ordinary film."

To this end, his team envisaged that in two years the development of a total biodegradable film (about 20 thousand yuan / ton), which is twice as expensive as the ordinary film, will be reduced to the acceptable range of farmers to truly open the huge market of biodegradable film.