Water balance and yield-increasing efficiency of irrigation of winter wheat under different irrigation schemes

Water is the most important limiting factor of wheat-maize double cropping system's production in the North China Plain (NCP). Water-saving agriculture is critical for social stability and sustainable economic development. To elevate irrigation efficiency in NCP, field experiments were conducted during three growing seasons of winter wheat at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences. Five irrigation schemes were designed in winter wheat seasons in the study area. The irrigation schemes included rainfed scheme (A) with no irrigation throughout the growing season, well irrigation scheme (B) with 100% field-capacity irrigation at all the stages, recovery water-stress irrigation scheme (C) with no irrigation at recovering stage and 80% field-capacity irrigation at all other growth stages, jointing-heading water-stress irrigation scheme (D) with no irrigation at jointing-heading stage and 80% field-capacity irrigation at all other stages, and then grain-filling water-stress irrigation scheme (E) with no irrigation at grain-filling stage and 80% field-capacity irrigation at all other stages. All the treatments had 3~4 replicates and irrigation was only done when moisture in the 0~100 cm soil depth was less than 65% of field capacity. The field irrigation experiments were conducted from October 2007 through June 2010. The results showed that evapotranspiration (ET) for treatments A, B, C, D and E were 251±58 mm, 482±48 mm, 352±44 mm, 388±22 mm and 324±53 mm, respectively. The volume of irrigation was positively related to yield in all the treatments. Yields for treatments A, B, C, D and E were 2 950±635 kg·hm^-2, 5 994±994 kg·hm^-2, 5 163±885 kg·hm^-2, 5 047±1 180 kg·hm^-2 and 5 249±975 kg·hm^-2, respectively. Irrigation efficiency varied from year to year in relation to precipitation trend. The effect of water on yield was therefore significantly different for the three years. In wet years, irrigation efficiency was 1.9 kg·m^-3, it was 0.4 kg·m^-3 in dry years and 1.6 kg·m^-3 in normal years.