Effects of the biodegradable film-based tray-free seedling system on seedling quality and ecological adaptability in cold-region rice

To reduce labor costs, mitigate plastic pollution, and enhance disease control in cold-region rice seedling nurseries, this study developed a biodegradable film-based seedling system.From 2022 to 2024, large-scale comparative field experiments were conducted over three consecutive years in seven major rice-producing cities and counties in Heilongjiang Province, including Tailai, Tonghe, and Fangzheng, to systematically analyze the effect of this technique on seedling morphology, biomass, vigor, and other key indicators, as well as its ecological and inter-annual adaptability. The results showed that, compared with traditional mechanical transplanting tray seedling raising (CK), the biodegradable film-based treatment (T1) increased seedling height, root length, stem base width,dry weight per hundred seedlings, and the classic strong seedling index (SRI) by an average of 6.82%, 8.97%, 9.52%, 10.26%, and 12.41%, respectively, while maintaining a stable root-shoot ratio and water metabolism.No bacterial wilt or seedling blight was observed throughout the experimental period, and no white plastic residue was detected.The total costof seedling raising was reduced by 15%-20%. Regionally, the technique performed best in high-biomass zones (e.g., Tonghe, Mishan) and balanced robust seedling zones (e.g., Suibin, Qing'an), while also showing positive effects in stress-prone regions. This technique demonstrates potential for improving seedling quality while reducing costs and plastic residue.Across 21 site-year combinations spanning seven major rice-producing regions, the system demonstrated consistent positive effects (T1/CK ratios >1.02) with the highest advantages observed in high-biomass regions (Tonghe and Mishan), confirming broad ecological adaptability.