Effect of plastic mulching on soil water use and spring wheat yield in arid region of northwest China

Abstract

The field experiments were conducted to study the evapotranspiration (ET), evaporation ( E), growth, yield and water use efficiency (WUE) of plastic-mulched spring wheat with hole planting in 1990 and 1991 under full and deficit irrigation at Zhangye Station of Water-saving Agriculture, Gansu Academy of Agricultural Science in northwest China. The experiment was designed to maintain minimum soil water content (MSWC) to different levels: 85%, 70%, 60%, 50%, 40% of field capacity in rooting depth and treatment to be nonirrigation. The treatments were laid out in a randomized complete block with four replications, and a non-mulched replication as control. The study indicated plastic mulched had higher ET than non-mulched due to increase of LAI. Seasonal ET was 269 mm for the plastic-mulch treatments with MSWC 40% and 765 mm with MSWC 85%, increased 19.8% and 2% than non-mulched, respectively. The ET rates of mulch treatments were lower before tillering, and higher after tillering. Plastic mulching could decreased evaporation from soil by 55% in comparison with non-mulched for the treatment of 60% MSWC. The yield was the highest with treatment of MSWC 60% in 1990 and 70% in 1991, and it was significantly higher than treatments of MSWC 40% and nonirrigation. However, there were not significant differences in yield when MSWC were between 50% and 85%. The water use efficiency (WUE) of the plastic-mulched treatment reduced with the increase in MSWC. They were 0.86 kg m −3 for the treatment of MSWC 85% in 1990 and 0.89 kg m −3 in 1991, significantly lower than MSWC 40–60% and nonirrigation. There were increases of 0.9–30.8% in ET and 4.0–110.3% in yield for all plastic-mulched treatment over non-mulch. The WUE with plastic mulch was 2–61% higher than non-mulch, and the difference increased with the decreasing of MSWC. The net seasonal income, benefit–cost ratio and net profit per mm of water used were bigger compared with non-mulched under less than 60% MSWC, however they became smaller from 60% up to 85%. Finally, results revealed that spring wheat mulched with plastic maintained higher WUE and net income than non-mulched under low soil water content, which makes it suitable for deficit irrigation in arid circumstance.