Abstract: For assessing the impacts of different water conditions on maize yield and environmental emissions of maize production, and for identifying the corresponding improvement measures, the meteorological data, and the data of fertilization, irrigation, soil properties as well as the development of maize growth were all collected in Taigu County, Shanxi Province from 2002 to 2016. The emissions of CO₂, NH₃, N₂O and nitrate leaching during the period of maize growing season with changing amounts of rainfall and fertilization were simulated by using the DNDC model. The life cycle assessment approach was applied to quantitatively evaluate the impact of maize growth on the resource use and environmental emissions; Then the relationships between rainfall and the resource consumption and emission were analyzed, and the reasonable amounts of fertilization and irrigation under different rainfall patterns were recommended. (1) When the rainfall ranged from 300 mm to 600 mm, the rainfall was positively correlated with the emissions of CO₂, nitrate leaching and NH₃ volatilization (P<0.05), while it was negatively correlated with N₂O emission. (2) When the rainfall was above 560 mm, namely abundant rainfall year, the comprehensive impact factor in the whole process of maize production ranged from 0.19 to 0.20, it was in the range of 0.17-0.27 in normal year with the rainfall from 380 to 560 mm, while it was 0.3 in dry year with the rainfall below 380 mm, respectively. The whole process of maize production had much high impacts on the environment in the dry year, followed by the normal year and abundant rainfall year. (3) The results of numerical simulation indicate that when the rainfall was below 380 mm and fertilization rate was fixed, with the increasing of the irrigation amounts, the yield was increased and the environmental emission was reduced, and the comprehensive impact factor declined to less than 0.2. Under rainfed conditions, the comprehensive impact factor will fall to 0.2-0.3 and the yield was only decreased by 3.15% when the fertilization rate was reduced to 210-315 kg·hm^-2; In the normal year, if the fertilization rate was decreased by 15% to 20%, the yield did not drop remarkably, but the impact on the environment was reduced obviously. Global warming potential, eutrophication potential, energy consumption and land use were correlated with the annual rainfall patterns. Irrigation has a great influence on the environment in the whole process of maize production. The sufficient irrigation led to high yield and less environmental impact, while the shortage of water resulted in low yield and much more environmental impact. Therefore, it is suggested to increase the amount of irrigation in dry years, and to decrease fertilization rate to reduce the environmental impact of maize production in rainfed areas.

Key words: life cycle assessment, denitrification-decomposition (DNDC) model, maize, water condition