Effects of combined plastic mulching and bunch seeding on soil-water use and spring wheat yield in and regions of Northwest China

Experiments to examine water use and yield improvement of plastic-mulched and bunch-seeded (PMBS) wheat were conducted at Zhangye, Gansu Province of northwest China between 1989 and 1992. Results showed that PMBS could efficiently reduce soil evaporation by 55% as compared with non-mulching. For the pre-seedling and seedling stages, despite the reduction of soil evaporation there was greater decline in soil water consumption than for non-mulched treatments. Maximum leaf area index (LAI) of spring wheat in a plastic-mulched field was about 1.5 times higher than the non-mulched one. So greater water consumption occurred and soil water content became less than that in non-mulched field for spring wheat, after the tillering stage. In addition, PMBS could improve yield, but the scale of the yield improvement declined with increasing irrigation amounts. Under conditions of limited irrigation, PMBS generated larger yield improvements, with the maximum increase being more than 100% that of yields with no mulching. In contrast. with adequate irrigation, the extent of yield improvement was little, water use efficiency (WUE) was no higher or even lower than that of non-mulched plots.