Studied on Physiological Mechanism　and Indices of Regulated Deficit　Irrigation in Summer Maize

Under the condition of control test, by cultivating in pots containing soil,with maize as material, the Regulated Deficit Irrigation(RDI)was studied.The results showed that RDI in maize was a practicable technology for watersaving,highyield and highefficiency.Under appropriate amount of water deficit at right stages,the transpiration rate decreased obviously,and the photosynthesis rate diminution was not obvious. There were supercompensative effects in photosynthesis and photosynthetic products accumulation after rewatering. The proportion of photosynthetic products distributed in the grains tends to increase. RDI was able to control vegetative growth,increase rootshoot ratio,raise root obsorption activities and promote antidrought resistance of plant. The indexes of RDI for watersaving and highyield in summer maize as follows:the stages of regulated water deficit is threeleavesjointing, the amount of water deficit is 45%θ_ｆ～65%θ_ｆ,or regulated water deficit during jointingheading,the amount of water deficit is 60%θ_ｆ～65% θ_ｆ,and the water deficit duration is 21 days. RDI increased yield by 25.24%, water consumption decreased by 15.41%, Water use efficiency(WUE) increased by 45.05% as compared with conventional irrigation.