Drought limits microplastic effects on soil greenhouse gas emissions by reducing microbial diversity

Extreme droughts and microplastics (MPs) accumulation in agricultural soils threaten ecosystem sustainability. We examined the impact of MPs and drought stress on greenhouse gas (GHG) emissions, along with the transformation patterns of carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) functional genes, and microbial communities in agricultural soils. This study aims to explore how the interaction between different types of MPs and drought stress modulates soil properties, microbial dynamics, enzymatic activities, and ultimately influences soil GHG emissions. Compared to conventional polyethylene (PE) MPs, biodegradable polybutylene succinate (PBS) MPs enhanced the generation of nitrous oxide (N₂O), yet drought conditions consistently suppressed overall GHG fluxes. The activities of soil enzymes associated with C, N, P, and S cycling were influenced by the type of MPs, drought, and soil properties. Notably, combined exposure to MPs and drought substantially altered soil metabolic profiles. PBS MPs under drought caused greater bacterial diversity loss and dominant taxa shifts than PE MPs. GHG emissions correlated with soil NH₄⁺-N, pH, dissolved organic carbon, and electrical conductivity, driven by carbon degradation, methane metabolism, and phosphorus cycling functional genes. This study highlights the interplay between MPs and drought in shaping GHG emissions and nutrient cycling, offering valuable insights for the management of alternative plastic use in sustainable soil management practices.