Preparation and Application of Potato Starch-based Liquid Mulch Film

ObjectiveThe widespread environmental issue caused by plastic mulch residues in agricultural soils urgently demands the development of biodegradable alternatives that can eliminate long-term pollution while maintaining agricultural productivity. This study focused on the development of a novel potato starch-based liquid mulch (BSLM) designed to provide temporary soil coverage, improve soil quality, and achieve complete degradation after fulfilling its functional role. This research comprehensively evaluated BSLM's material characteristics, its dynamic interactions with soil components, and its comparative effectiveness in promoting crop growth relative to conventional plastic mulch, with the overarching goal of validating its potential as a sustainable replacement in modern farming systems. MethodsBSLM was synthesized via free radical solution polymerization, involving NaOH pretreatment of potato starch followed by grafting with acrylic acid and crosslinking with N,N’-methylenebisacrylamide. The resulting film was characterized for its mechanical properties (tensile strain and load) and biodegradability through soil burial tests over 120 days. A pot experiment with lettuce was conducted under three treatments: BSLM application, plastic mulch coverage, and no mulch (control). Each treatment method was set up with three replicate groups. Soil temperature and moisture were monitored daily. At mid- and late-growth stages, soil samples were analyzed for bulk density, water-stable aggregate distribution, organic matter content, and pH value. Plant growth parameters, including germination rate, plant height, leaf number, and fresh weight, were measured at harvest. ResultsThe synthesized BSLM exhibited excellent mechanical strength and flexibility, and its longitudinal and transverse breaking strains were 280.5% and 493.1%, respectively. Its tensile loads in the longitudinal and transverse directions were 17.0 N and 21.0 N, respectively. The material demonstrated high biodegradability, with mass loss rates of 63.72%, 73.44%, and 95.78% after 1, 2, and 3 months of soil burial, confirming its environmentally benign nature. In the soil experiment, BSLM application significantly improved soil physical structure. It reduced soil bulk density to 1.36-1.39 g/cm3, compared to 1.45-1.47 g/cm3 in the blank group. The BSLM treatment also enhanced soil organic matter content, reaching 49.97 g/kg at mid-term and 43.27 g/kg at late-term. These values were significantly higher than those under plastic mulch. Most notably, BSLM profoundly improved soil aggregation, increasing the proportion of water-stable aggregates ＞0.25 mm to 43.57% (mid-term) and 46.77% (late-term), outperforming both the blank group (39.43%−39.73%) and the plastic mulch group (41.46%−42.90%). While BSLM's diurnal temperature retention (average 16.13-22.47 ℃) and moisture conservation (18.6% after 8 days without irrigation) were slightly lower than those achieved by impermeable plastic film, they were significantly superior to the unmulched soil. Regarding the crop response, BSLM dramatically increased lettuce seed germination to 84%, significantly higher than the 60% observed in the water-only control. At harvest, plants under BSLM treatment showed vigorous growth, with an average plant height of 15.30 cm, 13.67 leaves per plant, and a fresh weight of 254.37 g per plant. These growth and yield parameters were statistically equivalent to those obtained under conventional plastic mulch, demonstrating that BSLM could achieve comparable agronomic productivity without the associated environmental persistence. ConclusionsThis study successfully developed a high-performance potato starch-based liquid mulch film (BSLM) through a simple and scalable polymerization process. The material combines outstanding mechanical properties, rapid and near-complete soil biodegradability, and significant agricultural yield benefits. Its application could effectively improve key soil health indicators—such as structure, organic matter content, and aggregate stability—while providing optimal microenvironment regulation for crop growth. Most importantly, BSLM achieved equivalent performance to conventional polyethylene mulch in lettuce growth and yield, fully realizing its core agricultural productivity enhancement function. Leveraging renewable raw material sources, ease of operation, environmental safety, and cost-effectiveness, BSLM serves as a scientifically validated and commercially viable eco-friendly alternative, offering a sustainable solution to traditional plastic mulch. This technology holds significant potential for large-scale adoption in sustainable agriculture, particularly in regions vulnerable to soil degradation and plastic pollution.