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

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 rum 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 and circumstance. (c) 2005 Elsevier B.V. All rights reserved.