Effects of biodegradable film mulching on yield, grain quality, and soil metabolic characteristics of water-saving and drought-resistant rice

Introduction Film mulching is an effective water-saving cultivation technique, but its regulatory mechanism on yield and grain quality of water-saving and drought-resistant rice remains unclear. This study aims to investigate how biodegradable film mulching affects rice performance and rhizosphere soil metabolism under non-flooded conditions. Methods Field experiments were conducted in 2021 and 2022 using the water-saving and drought-resistant rice cultivar Hanyou 73 (HY73). Three cultivation treatments were applied: traditional flooded cultivation (TF), non-flooded unmulched cultivation (UM), and non-flooded biodegradable film mulching cultivation (BM). Yield components, grain quality parameters, and key enzyme activities involved in starch metabolism (SuSase, AGPase, StSase) were measured. A pot experiment was performed in 2023 to analyze rhizosphere soil metabolites using untargeted metabolomics. Results Compared with UM, BM significantly increased rice yield by 47.5% (2021) and 49.0% (2022), reaching levels comparable to TF with no significant difference. The UM treatment severely degraded grain quality: head milled rice rate decreased by 4.04% (2021), eating quality score dropped by 12.62% (2022), amylose content declined by 16.07% (2022), and chalky grain rate increased by 57.71% (2022) relative to TF. During the early grain-filling stage, SuSase, AGPase, and StSase activities in UM grains were significantly lower than those in TF and BM, though they showed compensatory increases at later stages. Metabolomics analysis revealed that BM regulated root microecology by reshaping the composition of soil fatty acids and other metabolites. Discussion Biodegradable film mulching enhances yield and preserves grain quality of water-saving and drought-resistant rice, primarily by optimizing starch synthesis enzyme activities during early grain filling and modulating rhizosphere soil metabolic profiles. These findings provide a theoretical basis for promoting sustainable and efficient rice cultivation using film mulching practices.