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Highlights • Biodegradable and plastic mulches were compared in drip irrigated cotton fields. • All mulches were effective in soil water and heat conservation and increasing yield. • Two biodegradable mulches performed similarly to plastic mulch in enhancing WUE. • Commercially available biodegradable mulch can be an alternative to plastic mulch. Abstract 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. [ABSTRACT FROM AUTHOR]

Mulched drip irrigation is regarded as an effective water-saving irrigation technique that is adopted widely in dryland regions. However, due to the lack of efficient mulch film recovery, residual plastic film fragments accumulating in soil nowadays pose a risk to agricultural production sustainability. To mitigate the pollution result from polyethylene (PE) film mulching and demonstrate the relationship between soil microenvironment, photosynthetic capacity, yield, and water use efficiency of cotton (Gossypium hirsutum L.) in various mulching practices, a two-year field experiment was carried out to test five mulching practices (sprayable degradable film mulching; biodegradable transparent film with an 80-day induction period mulching; biodegradable transparent film with a 100-day induction period mulching; conventional transparent polyethylene film mulching; no film mulching) in Xinjiang, Northwest China. The results showed that mulching significantly increased soil water content and temperature by 23.83% and 15.01% (average on two years) in topsoil compared to the bare soil surface, associated with a higher plant height, leaf area index, photosynthetic rate and aboveground biomass accumulation. Soil moisture, temperature, and crop height all significantly influenced cotton leaf photosynthetic rate, and soil moisture had the most significant impact (the direct path coefficient was 0.450). The highest cotton yield and WUE were observed in PE film mulching (5480.59 kg ha−1 and 1.35 kg m−3, respectively, average on two years) and the biodegradable transparent film with a 100-day induction period was comparable with PE film in yield increased and reduction of water loss (yield and WUE was 5357.51 kg ha−1 and 1.29 kg m−3, respectively, average on two years). The sprayable biodegradable film also had good wetting and warming effects on soil, but notably, sprayable film performances were still weaker than that in solid films. Compared to solid degradable films mulching, soil moisture, soil temperature, photosynthetic rate, yield, and WUE in sprayable film mulching was decreased by 5.55%, 7.19%, 31.41%, 5.31%, and 8.58% on average, respectively. In general, biodegradable transparent film with a 100-day induction period could significantly improve soil water-heat status, enhance cotton development, reduce water evaporation, increase cotton yield and WUE, which provides a cotton-cultivation option to control residual PE fragments pollution and maintained cotton yield. • Degradable films mulching increased irrigation water availability in Northwest China. • Soil moisture had the greatest impact to cotton leaf photosynthetic rate. • Sprayable biodegradable had a good wetting and warming effects on soil. • The compatibility of water-heat conservation of sprayable film was weaker than solid films. [ABSTRACT FROM AUTHOR]

• Cotton yields were significantly increased by drip irrigation with plastic mulching in oasis region. • Drip irrigation with plastic mulching significantly increased soil moisture and temperature. • Drip irrigation with plastic mulching significantly increased soil CO 2 emissions. • Total CO 2 emissions in narrow rows near drip tape were highest, followed by wide rows and bare land. As the second carbon storage pool, soil is easily influenced by human activities. Mulched drip irrigation is a water-saving irrigation technique used widely in arid and semi-arid regions. However, information about the response of CO 2 exchange to mulched drip irrigation, such as the wetter and warmer soil, is limited. To identify the carbon emissions effects of mulched drip irrigation, we carried out a field experiment using drip irrigation with and without clear plastic mulching during the cotton growing seasons of 2015 and 2016. We monitored the temporal and spatial variation of soil moisture, soil temperature, cotton growth stage, biomass, lint yield, CO 2 emissions, and the relationship between soil respiration rate and soil climate. The results showed that plastic mulching drip irrigation increased soil moisture and soil temperature, especially during the early and middle growth stages of cotton. The soil respiration rate was related positively to the higher soil temperature and moisture conditions promoted by plastic film mulching, although the coefficients of determination were low (R2 were 0.480 and 0.205, corresponding p-value was both 0.000, respectively). The highest value of soil respiration was obtained within the narrow rows under the drip tape, regardless of the practice of mulching or not. The soil respiration rate under plastic mulch in the narrow and wide rows were on average 28.35 % and 22.48 % higher than non-mulched control. Meanwhile, the amount of total CO 2 emissions was significantly increased by 25.34 % and 28.90 % in these same rows, respectively (p-values were 0.006 at narrow rows and 0.010 at wide rows in the first year, and 0.000 at same rows in the second year). The differences of CO 2 emission in the bare soil was not significant between mulched plots and non-mulched control (p-values were 0.757 and 0.918 in the first and second growing seasons, respectively). In addition, plastic mulching significantly improved the biomass and yield of cotton, by 61.49 % and 12.83 % on average (p-values were 0.034 and 0.039 in 2015, 0.024 and 0.032 in 2016), respectively. The results indicate that the application of drip irrigation under plastic mulch could increase soil water content and temperature, promote cotton growth, and improve lint yield. However, it may also lead to increased CO 2 emissions, which can intensify the warming of the climate. [ABSTRACT FROM AUTHOR]