Straw Return Enhances Photooxidative Disintegration of Mulch Film and Microplastics Formation in Farmlands.
Zhang X, Lin Y, Wu S, Cao T, Hou S
Microplastics
If you mulch your vegetable beds with plastic sheeting and compost straw or plant debris back into the soil, you may be accelerating the very plastic fragmentation that ends up in your homegrown food.
Farmers often leave crop leftovers like corn stalks on their fields to feed the soil, and they also cover the ground with plastic sheeting to keep moisture in and weeds out. Scientists discovered these two practices clash: the decomposing plant material releases natural compounds that, when hit by sunlight, generate a highly reactive form of oxygen that tears apart the plastic into tiny fragments. Those fragments — microplastics — can then build up in the soil and even reduce how well crops grow.
Key Findings
Maize straw amendment significantly increased oxidation and fragmentation of low-density polyethylene (LDPE) mulch films compared to unamended soil, with straw-derived organic matter producing markedly higher levels of singlet oxygen than biochar amendment.
Singlet oxygen generated by straw-derived natural organic matter preferentially attacks the amorphous regions of LDPE polymer chains, causing chain scission and embrittlement that accelerates microplastic formation.
Canopy-scale modeling linked experimentally measured microplastic accumulation to reductions in photosynthetic performance, projecting maize yield losses exceeding 5% under representative field conditions.
chevron_right Technical Summary
Returning crop straw to fields — a common practice to improve soil health — unexpectedly speeds up the breakdown of plastic mulch films into microplastics. The organic matter released by decomposing straw boosts the production of a reactive oxygen species that attacks and fragments plastic, potentially cutting corn yields by more than 5%.
Abstract Preview
Plastic mulching is widely used in modern agriculture but represents a major source of microplastics in farmlands. Here, we show that straw return, a common practice to enhance soil fertility and c...
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