Soil suffers from 'white chronic disease'

Plastic film is the core production material for dryland agriculture and facility planting in China. With the advantages of insulation, moisture retention, grass suppression and yield increase, it has become a "standard" for farmland planting for decades. But little known is that the plastic film fragments left in the fields over the years have formed a continuous accumulation of pollution problems in the soil, becoming an incurable "white chronic disease" of arable land. In recent years, biodegradable plastic film has gradually been promoted and regarded as a good solution for pollution control, but its actual performance in the field has far from achieving the ideal effect of "one use cure".
The annual consumption of plastic film in China reaches millions of tons, covering hundreds of millions of acres of arable land. Traditional plastic film is mostly made of ultra-thin polyethylene material, which is fragile in texture and easily shattered after sun exposure, weathering, and agricultural machinery plowing. Due to the difficulty and high cost of manually picking up small residual films, mechanical cultivation can also tear and press the residual films into deep soil. In addition, extensive treatment methods such as incineration and disposal result in a large amount of plastic fragments remaining in the fields all year round, stacking layer by layer to form an underground "plastic layer". What's even more serious is that the natural degradation cycle of polyethylene film can last for hundreds of years and cannot be decomposed by soil microorganisms. Pollution will only accumulate and continue to worsen year by year.
The damage of plastic film residue to soil ecology is comprehensive and irreversible. Residual film fragments can disrupt the soil pore structure, reduce the permeability of cultivated land, hinder the rooting of crop roots, directly affect water and fertilizer absorption, and cause crop yield reduction. At the same time, residual film and derived microplastics can disrupt the balance of soil microbial communities, inhibit the cycling of soil carbon, nitrogen, and phosphorus nutrients, and lead to sustained decline in farmland fertility. In addition, microplastics can also disturb the living environment of soil animals such as earthworms, affecting the ecological chain of farmland, and long-term accumulation will seriously damage the quality of farmland and agricultural production capacity.
To solve the problem of residual film pollution, fully biodegradable plastic film has become the mainstream alternative solution. Qualified biodegradable plastic film can naturally decompose into water, carbon dioxide, and organic matter in the field, with no residue or pollution, and its planting performance such as insulation and moisture retention is basically the same as traditional plastic film, providing a new path for farmland pollution control. Various regions have also introduced subsidy policies to help promote it.
However, field practice has shown that biodegradable plastic film is not a universal cure, and there are still many practical shortcomings. In terms of cost, its price is 2 to 3 times that of traditional plastic film, which increases the burden on farmers' planting and generally reduces the willingness to promote in grain producing areas. In terms of adaptability, the degradation rate is highly dependent on temperature and humidity, and the degradation cycle is significantly prolonged in low-temperature and high-altitude areas in the north, which can lead to post harvest residue problems; In some scenarios, the plastic film may break prematurely, losing its role in crop management and protection. At the same time, the agricultural inputs market is mixed with good and bad, and many "pseudo degradable plastic films" only break in the short term, still producing microplastic pollution and misleading farmers' choices.
Agricultural experts say that the treatment of plastic film pollution cannot be achieved overnight, and cannot rely solely on degradable plastic film as a substitute. We need to establish a comprehensive governance system that includes source control, end of pipe recycling, technological substitution, and market supervision coordination: strictly control the circulation of ultra-thin non-standard plastic film and reduce it from the source; Improve the industrial chain of mechanized recycling and resource utilization of residual films; Promote the degradation of plastic film according to local conditions and optimize subsidy policies; Strictly investigate inferior and pseudo degradable products, while strengthening agricultural technology popularization, and transforming farmers' extensive planting habits. Only by taking multiple measures and implementing long-term management can we gradually cure the "white chronic disease" of soil,Protect the ecological security of cultivated land.