Biodegradable mulching film with an optimum degradation rate improves soil environment and enhances maize growth

Biodegradable film is considered as a promising alternative to polyethylene film in rainfed farming of arid and semi-arid regions, since the widespread use of polyethylene film has led to many negative effects, such as environmental pollution and land degeneration. In order to identify an optimal biodegradable film for summer maize, field experiments were conducted to investigate the effects of biodegradable films with different degradation rates on soil water storage (SWS), soil temperature, soil organic carbon (SOC), the growth stages, grain yield, water use efficiency (WUE), and economic return over three growing seasons from 2014 to 2016. Three biodegradable films one with a fast degradation rate (B1), one with a moderate degradation rate (B2), and one with a slow degradation rate (B3), were compared with a polyethylene film (P) and a flat planting system without film mulching was used as the control (CK). The degradation progress of the three types of biodegradable film (B1, B2, and B3) was on time or delayed by about 10 days during normal years (2014 and 2015 seasons) and advanced by 10–20 days during the extreme year (2016 season, plants affected by both lodging and high temperature). Soil temperature and SWS increased significantly under B1 (3.6 °C higher at 5 cm and 2.4 °C higher at 25 cm) and B2 (3.7 °C higher at 5 cm and 2.3 °C higher at 25 cm), compared with CK before the biodegradable film degraded. However, there was no difference in soil temperature and SWS after the biodegradable films B1 and B2 had degraded. The B3 and P treatments led to similar soil temperatures and SWS values throughout the maize seasons. After 3 years of experiments, the SOC levels ranked from high to low were 2.85%, 5.30%, 11.72%, and 15.07% higher in CK than that in B1, B2, B3, and P, respectively. The season length was the longest in B2 (117, 117 and 112 d) for all three seasons. Average grain yield, WUE, and net revenue in B2 were 18.40%, 25.10% and 32.97%, 11.90%, 6.62% and 20.46%, 11.43%, 6.82% and 15.71%, and 32.50%, 45.64% and 41.05% higher than in B1, B3, P, and CK, respectively. The results suggested that biodegradable film with a moderate degradation rate could improve the soil environment, promote maize growth, increase net revenue and reduce loss of SOC relative to B1, B3 (no significant difference with B1 in SOC level) and P. Therefore, B2 was the best biodegradable film for summer maize production in regions with sub-humid drought-prone climates.