Evaluation on the responses of maize (Zea mays L.) growth, yield and water use efficiency to drip irrigation water under mulch condition in the Hetao irrigation District of China

Hetao Irrigation District (HID) is characterized by less rainfall and high evaporative, but it is a main grain production region in China. Increasing water use efficiency is an appropriate way to fulfill the sustainable agriculture development because the allocated water for HID will be reduced in the future. In this study six irrigation treatments with irrigation amounts being the 20, 40, 60, 80, 100, and 120% of crop water requirement (ETc) were carried out for maize crop (Zea mays L.) in the HID under mulch-dripped irrigation condition in 2013 and 2014 years. Soil water and electrical conductivity, plant growth factors, harvest factors and yield were investigated, and crop actual evapotranspiration (ETcact), water use efficiency (WUE) and irrigation water use efficiency (IWUE) were calculated. Results showed that soil water and salt mainly varied in the upper 60 cm soil layer. At harvest, salt accumulation was found in the upper soil layer and the highest salt accumulation was in the least irrigation treatment. Growth factors and harvest factors were reduced significantly (P < 0.05) for irrigation depth of less than 40%ETc compared to 80-120%ETc, but they were not significantly (P > 0.05) different from 80 to 120%ETc. The highest grain yield were found at 100%ETc, then yield decreased with irrigation depth decreasing due to the reductions of ear size and 100-grain weight. ETcact ranged from 200 to 430 mm in the two seasons, and linearly increased with the irrigation depth increasing. The highest WUE was found at 60%ETc, while IWUE was decreasing with irrigation depth increasing. Fully considering maize yield, water use efficiency, soil salt balance and water resources availability of Yellow river, full irrigation with 100%ETc is recommended with the objective of the highest yield when water resources can satisfy water demand of irrigation and economic development, while water deficit of 20-30% is recommended with the objective of getting the highest WUE and little yield loss (4-8%) under mulched drip irrigation in HID.