Biodegradable film mulching (BFM) is a promising alternative to conventional plastic film mulching (PFM) for overcoming plastic pollution in dryland agriculture. However, its sustainability hinges on understanding its impact on soil nitrogen (N) supply for crop production and subsequent environmental consequences. We conducted a field experiment with 15 N tracing to quantify gross N transformation rates, complemented by measurements of N cycling functional genes, enzyme activities, plant N uptake and gas emissions. Our results demonstrated that BFM maintained maize yield and plant N uptake comparable to PFM, which is achieved by altering the soil N transformations. BFM stimulated dissimilatory NO 3 − reduction to NH 4 + ( DNRA ) by 38%–56% throughout the maize growth stages and enhanced gross nitrification by 28% during the mid-to-late stages, thereby increasing soil NH 4 + and NO 3 − availability. These changes in process rates were linked to an altered soil microbial community structure and an increased abundance of key functional genes (e.g., amoB , napA ) under BFM. Although BFM decreased the N 2 O emissions by 0.3 kg N ha −1 , it increased NH 3 volatilization by 29% owing to higher NH 4 + production. In rhizosphere soils, BFM also increased gross N mineralization and nitrification compared with PFM, indicated a high capacity for N supply for BFM. Structural equation modeling revealed that the film mulching type regulated gross N transformations primarily by altering microbial functions, which subsequently changed plant growth and N loss. BFM enhances soil N supply and reduces N 2 O emissions by stimulating DNRA and nitrification, mediated by altered microbial communities and functions, but at the cost of increased NH 3 volatilization. This study provides a mechanistic understanding of how BFM changes N cycling and N losses, offering a scientific basis for designing sustainable mulching systems in dryland agriculture. Concept of N transformations and fate in soil under conventional (PFM) and biodegradable film mulched (BFM) planting system describing the mechanisms of N supply and N loss. DNRA , the dissimilatory reduction rate of NO 3 − to NH 4 + .
Zhang et al. (Fri,) studied this question.