Biodegradable mulch films promote sugarcane growth by regulating rhizosphere microbial communities and predicted...

Conventional polyethylene (PE) mulch causes persistent soil plastic pollution; biodegradable mulch films (BMFs) may avoid this, but their effects on sugarcane rhizosphere microbes and yield are unclear.

Using a field trial in Yunnan, we compared polyethylene mulch (PM) with two PBAT/PLA-based biodegradable mulch films (BMFs) differing in thickness (Thick Film, BTK, 0.008 mm; Thin Film, BTH, 0.005 mm). Rhizosphere soil (0-40 cm) physicochemical properties, bacterial (16S) and fungal (18S) communities, predicted microbial functional potentials, and sugarcane agronomic traits were analyzed.

BMFs degradation released organic carbon that significantly altered the rhizosphere microenvironment, increasing soil pH, organic matter, and available potassium relative to PM. These physicochemical changes drove microbial community differentiation. Compared with PM, BMFs increased the relative abundances of Chloroflexi, Acidobacteria, and Basidiomycota, while decreasing Actinobacteria and Ascomycota (p < 0.05). BMFs also enhanced microbial α-diversity, with bacterial diversity being higher under BTK and fungal diversity under BTH. Neutral model analysis revealed that bacterial community assembly was dominated by stochastic processes; however, BMFs reduced dispersal limitation and strengthened deterministic environmental filtering, particularly under the BTH treatment, due to enhanced microhabitat heterogeneity from faster degradation. These community shifts were associated with enriched predicted sulfur (dsrAB) and nitrogen (nosZ, nif) cycling genes and more complex, cooperative bacterial-fungal interaction networks, with BTH exhibiting higher network complexity and positive interactions. These microbial responses were associated with improved sugarcane performance. Compared with PM, BMFs increased single stalk weight by 8.76%-11.68%, millable stalk number by 4.99%-7.38%, and cane yield by 17.11%-17.40%.

Collectively, our results demonstrate that BMFs, through degradation-driven microhabitat alteration, strengthen deterministic assembly, promote functionally specialized taxa and cooperative networks, and enhance predicted nutrient cycling potentials, thereby improving sugarcane productivity and offering a sustainable alternative to PE mulch.