Effects of mulching biodegradable films under drip irrigation on soil hydrothermal conditions and cotton (Gossypium hirsutum L.) yield

Biodegradable mulches are advocated as an alternative to plastic mulches. Here, we carried out an experiment in Xinjiang, an arid region in China, to demonstrate the effects of mulching biodegradable films under drip irrigation on soil conditions and cotton (Gossypium hirsutum L.) yield in 2015 (with less precipitation) and 2016 (with more precipitation). Plastic mulch made from polyethylene (PE) and four types of biodegradable mulch were compared, namely, BD1 to BD4, with different levels of thickness and induction periods. Our results indicated that PE mulch was the most efficient in soil water and heat conservation. Biodegradable mulches performed similarly in warming the soil in both years, which increased topsoil (5–20 cm depth) temperature than no mulching in the cropping season by 0.66 °C and 0.61 °C in 2015 and 2016, respectively. The effect of mulching on increasing soil water storage was stronger in the wet year. The increased soil water storage (0–100 cm depth) by biodegradable mulches than no mulching was 113 mm and 194 mm in 2015 and 2016, respectively. Earlier onset of the phenological events of cotton growth was similar between PE mulch and biodegradable mulches. Mulching shortened the number of days from sowing to cotton maturity by 4 days and 10 days in 2015 and 2016, respectively. Compared with no mulching, biodegradable mulches achieved better performance in enhancing cotton yield and water use efficiency (WUE) in the dry year (916 kg ha−1; 1.85 kg ha−1 mm−1) than in the wet year (568 kg ha−1; 1.22 kg ha−1 mm−1). Although PE mulch resulted in the highest yield, there was no significant difference in WUE between PE mulch and BD1 or BD2. Therefore, some of the commercially available biodegradable mulches can be used as a competitive alternative to plastic mulch to enhance crop yield and control soil pollution.