By Liu Jialei, Chinese Academy of Agricultural Science
In recent years, China has consumed nearly 1 500 000 tons of mulch film, which covered more than 40 types of crops and all the domestic planted regions, generating about a direct profit of RMB140 billion to Chinese agricultural production. The application of mulch film has promoted agricultural production and income, but the wasted mulch film in the field has deteriorated white pollution and been given extensive concerns.
Mulch film has provided firm technological support for the efficient agricultural production of China
China’s annual crop planted area is more than 2 400 000 000 mu and nearly 300 000 000 mu of major crops are covered by mulch film, coverage rate of crops reaching 13%. Four major reasons have contributed to the fast growth of mulch film. Firstly, mulch film is good for warming, making planting crops at high latitude area possible. Secondly, mulch film is good at keeping water. Thirdly, mulch film can reduce more than 70% biomass of weeds and consequently reduce the weeding work and the amount of herbicide used. The cost for agricultural production was thus lessened. Fourthly, mulch films can bring an obvious growth for the crop yield. Except for the main effects above, some functional mulch films have the function of spectrum adjustment, which play an important role in fruit coloring, expelling insects of farmland, sterilizing soil, improving the efficiency of fertilizers.
Pollution from mulch films has become a major factors impeding the sustainable development of agriculture of China
Currently, the mulch film residues have brought negative influence and even harm to the agricultural production and environment of some regions especially in the northwestern China where more mulch film has been used. In part of farmlands, the residues of mulch film have totaled more than 25 kg/mu, greatly impeding the farm operation and crop growth. The worse is the severe impact to the food security. As a result, the pollution from mulch film has become an important factor harming the sustainable development of China’s agriculture both in terms of soil protection and food security.
Full biodegradable mulch film replacement is one of the key technologies in solving the pollution of mulch film
At present, the main solutions for pollution of mulch film include recycling of residual mulch film and degradable mulch film replacement technology. The relevant policies formulated by Ministry of Agriculture and Rural Affairs of PRC recommended high strength mulch film to be applied for recyclable crops, and suggested increasing recycling rate, reducing sorting difficulty and improving the efficiency of high-valued utilization of mulch film residues.
Degradable mulch film replacement has given birth to desirable economic, social and ecological benefits. The crops for which full biodegradable mulch film has been applied in large area include potatoes and organic rice.
There are urgent needs for high-quality full biodegradable mulch film from market
There are nearly 100 enterprises nationwide engaged in full biodegradable mulch film related businesses, such as the research and development of biodegradable resin, additives and new film products. Till now, the quality and performance of full biodegradable mulch film have been greatly improved especially in its safety, operability, functionality, controllability and economy. In 2019, there were 100 000 mu of farmland in which full biodegradable mulch film was applied, mainly in the Xinjiang Uygur Autonomous Region, Yunnan, Gansu, Hebei provinces, the Inner Mongol Autonomous Region and Northeastern regions including Heilongjiang, Jilin and Liaoning provinces.
Currently, the biodegradable mulch film is being urgently needed in following aspects. Firstly, crops like garlic and peanut desire 5-um ultrathin degradable mulch film because of their special planting techniques and growth process. Secondly, the crops such as potato and beet, which have particular requirements for the water and air permeability of soil during their root expansion period. To replace PE mulch film with full biodegradable mulch film will be able to promote the quality and yield of these crops. Thirdly, the cost of use and recycling of general mulch film has exceeded the cost of full biodegradable mulch film.
The functions of full biodegradable mulch film are expected to be improved
The quality and functions of degradable mulch film have been largely strengthened during recent years. But it is still not be possible to cover all areas and all crops with only one formula as traditional PE mulch film does. Compared to PE mulch film, degradable mulch film needs being improved in the following performances. The first is that its water vapor transmittance rate (WVTR) is relatively high. The second is that its weed control ability is weak. The third is its thermal insulation is far from being satisfactory. The fourth is that big problems in the extension of function period and accurate control need to be solved.
Full biodegradable mulch film expects a promising future
The issue of Soil Pollution Prevention and Control Law of China has provided legal basis for the fast popularization of biodegradable mulch film. Meanwhile, series of regulations have directed fund to the popularization of mulch film, including The Program of Act against Agricultural and Rural Pollution, The Suggestion of Taking Five Acts to Develop Green Agriculture, The Notice of Ministry of Agriculture and Rural Affairs to Launch Mulch Film Recycling Program, The Notice of Ministry of Finance and Ministry of Agriculture and Rural Affairs to Launch Pilot Program of Recycling Mulch Film. As the capacities of materials of degradable resin keep growing, the material price will be declining continuously and the over high price of the materials is expected to be alleviated. More types of degradable resin have been put into production and producing techniques have been increasingly improved. Therefore, the product quality will be greatly promoted as the degradable mulch film application area and the crop types will be increased. As the development of mulch film formula goes further and the assessing work of its security and suitability deepens, degradable mulch film related standards will be gradually improved.