Biodegradable film mulching alters soil C, N, P and S cycling via mediating microbial communities in dryland.

Background: Biodegradable film mulching, induced the generation of microplastics (MPs), may affect nutrient cycling and ecosystem functions. However, its influence on carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) cycling and the underlying driving force remains lacking. Through a 4-year field experiment comparing conventional plastic mulch (M), biodegradable plastic mulch (BM) and un-mulch control (NM), we evaluated the impact of different film mulching measures on the abundance of MPs and how MPs affect ecosystem functions including C, N, P and S cycling.

Results: BM resulted in maximal accumulation of MPs across experimental treatments, with particular enrichment of small-size (< 0.25 mm) MPs. BM slightly reduced C, N, P and S gene abundances compared to M in bulk soils, whereas it was similar to NM. However, in rhizosphere soils, BM significantly decreased C, N, P and S cycling-related gene abundances compared to M (54%-60%) and NM (64%-69%). Correlation analysis revealed that the abundance of MPs and soil nutrient and microbial community structure were the main factors affecting soil C, N, P and S cycling. Compared to M, BM increased the abundance of MPs and enhanced soil C (9%), N (23%) and P (9%) contents in rhizosphere soils, thus reducing microbial competition for nutrition and altered microbial interactions, and consequently decreasing C, N, P, and S cycling gene abundance.

Conclusion: Different film mulching alters soil nutrient cycling via mediating microbial communities. BM mitigates excessive nutrient consumption through functional gene regulation at the same time as maintaining agricultural productivity comparable to M. Our findings provide a microbial perspective on the dual role of BMs in accumulation of MPs and nutrient conservation, highlighting its potential as an environmentally balanced agricultural practice. © 2025 Society of Chemical Industry.