Effects of irrigation before sowing and plastic film mulching on yield and water uptake of spring wheat in semiarid Loess Plateau of China

Abstract To improve crop yield in semiarid areas, it is valuable to combine irrigation of harvested rainwater with plastic film mulching technology. Limited irrigation after mulching is not usually practiced. This research was to study the combination of pre-sowing irrigation and film mulch and its effect on spring wheat grain yield in semiarid Loess Plateau in China. Four treatments were employed: (1) C—control, without pre-sowing irrigation and without mulching; (2) I—pre-sowing irrigation of 30 mm without mulching; (3) M—plastic film mulching without pre-sowing irrigation; and (4) IM—30 mm pre-sowing irrigation plus mulching. Plastic films in mulched plots were removed at 60 days after sowing (DAS). Although soil water evaporation in the mulched treatments is reduced by film mulch, soil water content in the mulched treatments was lower than in the non-mulched treatments by 60 DAS. Pre-sowing irrigation increased evapotranspiration, but the percentage of water supply from the soil profile in the overall evapotranspiration is just within the range from 7.1 to 33.5%. Rainfall and irrigation during the growing period provide most of the water for evapotranspiration, especially in very dry years. The grain yield was 29.4% greater in treatment IM in 1999 and 112.4% greater in 2000 compared with control, and 35.7% greater in 1999 and 47.3% greater in 2000 compared with the treatment M. Correlation analysis revealed that the spikelet number and the fertile spikelet number were the key factors determining grain yield formation, at least in these two years. The greatest water-use efficiency (WUE) was found in treatment IM for both years, and was significantly higher than in other treatments. The WUE was higher in the wet year of 1999 than in the dry year of 2000. The combination of pre-sowing irrigation with film mulching increased the soil temperature in the seedling stage, reduced the water deficit, and achieved the highest shoot biomass, grain yield, and water-use efficiency of the 2 years. It is, therefore, concluded that the combination of pre-sowing irrigation with plastic film mulching works well in increasing plant growth and yield of spring wheat and can be adopted for spring wheat production in the semiarid areas.