Integrated effects of residual plastic films on soil-rhizosphere microbe-plant ecosystem

Intensive application of low-density polyethylene mulch films has resulted in substantial accumulation of residual plastics in agricultural soil. Although considerable concerns have been raised on the residual plastic pollution, their impacts on the soil-rhizosphere microbe-plant ecosystem have not been fully elucidated. In this study, we used a pot experiment to determine the effects of residual plastic films with different sizes (La, Ma, Mi and Mx) on properties, enzyme systems and nutrients of soil, composition of rhizosphere microbial community, and physiology, growth and stress response of rice plants. Residual plastic films significantly decreased soil bulk density and increased soil porosity, leading to the alteration of extracellular enzyme activities, and accumulation of dissolved nitrogen (NO3-N + NH4-N). The structures of both bacterial and fungal communities were significantly changed by residual plastic films with rhizosphere microbes more sensitive to small-sized plastics. Plant growth was inhibited to different extents by residual plastic films with different sizes. The weighted gene co-expression network analysis (WGCNA) showed that photosynthesis and carbon fixation of rice plants were repressed by residual plastic films, due to the reduced chlorophyll content and rubisco activity. In addition, the endogenous jasmonic acid and antioxidant enzyme system were induced to activate tolerant responses in rice plants to the stress imposed by residual plastic films. The partial least squares path models (PLS-PMs) revealed that residual plastic films had direct and/or indirect effects on the soil-rhizosphere microbeplant system.

Automated summary

Extensive usage of low-density polyethylene mulch films has caused the accumulation of plastic waste in agricultural soil. However, the impact of residual plastics on the soil-rhizosphere microbe-plant ecosystem remains unclear. This study investigated the effects of residual plastic films of different sizes on soil properties, enzyme systems, nutrient content, microbial community composition, and growth response of rice plants. The findings revealed that residual plastic films affected soil characteristics, enzyme activities, microbial communities, and hindered plant growth. The presence of residual plastic films suppressed photosynthesis and carbon fixation in rice plants, while inducing stress responses and changes in antioxidant enzyme levels.