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Effect of polylactic acid microplastics on soil properties, soil microbials and plant growth
Summary
Researchers tested whether microplastics from biodegradable polylactic acid plastic, often proposed as an eco-friendly alternative to conventional plastic, affect soil health and plant growth. High concentrations of these biodegradable microplastics reduced soil pH, altered the ratio of carbon to nitrogen, decreased plant growth, and shifted soil microbial communities. The study suggests that even biodegradable plastics can negatively affect agricultural ecosystems when they break down into microplastic-sized particles.
Biodegradable plastic is considered one of the most promising alternatives to agricultural mulch. However, the impact of biodegradable microplastics on agricultural ecosystems is still lacking. We conducted a controlled experiment with polylactic acid microplastics (PLA MPs) to examine the effects of biodegradable plastic on soil properties, corn growth, the microbial community and hotspots of enzyme activity. The results showed that PLA MPs in soil significantly reduced the soil pH value but increased the soil C:N ratio. High levels of PLA MPs significantly reduced the biomass of plant shoots and roots as well as chlorophyll, leaf C and N and root N contents. PLA MPs increased bacterial abundance but decreased the abundance of dominant fungal taxa. As the level of PLA MPs increased, the soil bacterial community structure became more complex, while the fungal community became more singular. The results of the in situ zymogram showed that low levels of PLA MPs increased the hotspots of enzyme activity. The effect of PLA MPs on enzyme activity hotspots was regulated by a combination of soil properties and microbial diversity. Generally, the addition of PLA MPs at high concentrations will have a negative impact on soil characteristics, soil microbials and plant growth in a short period of time. Therefore, we should be aware of the potential risks of biodegradable plastic to agricultural ecosystems.
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