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Field application of biodegradable microplastics has no significant effect on plant and soil health in the short term

Environmental Pollution 2022 64 citations

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Researchers conducted a field study to test whether biodegradable polylactic acid microplastics affect oat and soybean growth or soil health over one growing season. They found that neither fiber nor powder forms of the biodegradable microplastics had significant effects on soil enzyme activities, plant biomass, or crop yield. The study suggests that biodegradable microplastics may not pose a significant short-term threat to agricultural ecosystems and could serve as a viable alternative to conventional plastics.

Polymers

Bioplastics (biodegradable plastics) potentially offer an encouraging alternative to conventional (petroleum-based) plastics. In practice, bioplastics inevitably generate a large number of bio-microplastics (bio-MPs, diameter <5 mm) during the degradation progress. However, the impact of bio-MPs on plant and soil health within agroecosystems remains incomplete. Here, a field study was conducted to investigate the effect of two shapes (fiber and powder) of pure polylactic acid (PLA) bio-MPs on oat (Avena sativa L.) and soybean (Glycinemax (L.) Merr.) growth and soil health. Our results showed that PLA application at a representative soil loading rate of 0.2% (w/w) had no significant effect on soil enzyme activities, soil physicochemical properties (soil water content, pH, etc.), root characteristics, plant biomass, and crop yield. Thus, we conclude that soil quality, plant health, and ecosystem multifunctionality were not affected by PLA over one growing season (5 months) in the presence of either bio-MP shape (fiber and powder) for either crop species (oat and soybean). Overall, PLA based bio-MPs may not pose a significant threat to agroecosystem functions in the short term (days to months) in the field, thus may provide a viable environmentally benign solution to replace traditional non-biodegradable plastics in agroecosystems.

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