Biodegradable film mulching improves soil temperature, moisture and seed yield of winter oilseed rape (Brassica napus L.)

- Seed yield did not differ significantly between conventional PE film mulching (PM) and biodegradable film mulching (BM).
- BM produced longer taproots and higher lateral root mass density in 20-30 cm soil layer.
- BM produced lower seed erucic acid and glucosinolate contents compared to PM.

Biodegradable film has been proven to be a good alternative to conventional polyethylene (PE) film for crops such as maize and cotton, but its suitability for winter oilseed rape (Brassica napus L.), one of the most important oilseed crops worldwide, has not been fully investigated. We conducted a three-year field experiment to systematically analyse and compare the effects of conventional PE film mulching (PM), biodegradable film mulching (BM), and no film mulching (CK) on soil temperature, soil water storage, water use efficiency (WUE), root growth, and yield for winter oilseed rape. The effects of increasing soil temperature and soil water storage were similar for BM and PM and were significantly higher than for CK before 150 days after sowing (DAS), but the increases of soil temperature and soil water storage were significantly lower for BM than PM after 150 DAS due to the degradation of the biofilm. The taproots of the rapeseed extended 1.7 cm significantly deeper into the soil for BM than PM, and the mass density of lateral roots in the 20-30 cm soil layer was 18-26 g m−3 significantly higher for BM at maturity stage. Evapotranspiration (ET) was significantly higher in BM than PM but still significantly lower than in CK. The average ET in BM was 10.0% higher than in PM and 10.4% lower than in CK. Yield and WUE did not differ significantly between BM and PM. Average yield and WUE in BM were 5.8 and 14.3% lower than in PM and were 38.4 and 54.5% higher than in CK. The seed content of erucic acid and glucosinolate, harmful to human health, was lower in BM than PM, while seed oil, protein, and oleic acid contents did not differ significantly between BM and PM. Biodegradable film is thus recommended as a viable option to the conventional PE film for the production of winter oilseed rape.