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The share of fossil-based resources in the implementation of agricultural activities in Iran is very high. In this context, it is important to determine the environmental impacts of energy use in agricultural activities. The purpose of this study was to evaluate and compare the energy consumption and total environmental impacts of irrigated and rainfed wheat production in central Iran, Mahyar plain. For this purpose, data were collected from 120 irrigated and 90 rainfed wheat farms in three different farm size (<2 ha, 2-4 ha and more than 4 ha), through questionnaires and site visits. In this study, standard ISO life cycle assessment methodology was used to evaluate the total impact of all consuming inputs on environmental pollution and show the main hotspot in the production chain. Results of energy analyses showed that large farms used more energy per unit of farm land than that of small farms. Farmers also used higher input energy for irrigated wheat in comparison with rainfed system. The overall energy use efficiency for per unit farm of irrigated wheat production was only half of rainfed wheat production. Results of Life Cycle Assessment (LCA) models show that rainfed wheat actually produced more pollutions than irrigated wheat production because of lower yield in ha. In this study, the rate of Abiotic Depletion (AD) and Acidification (AC) impact were 0.002-0.003 kg Sb eq and 8.991-11.863 kg SO 2 eq for wheat production (irrigated and reainfed), respectively. Also the Ozone Layer Depletion (OLD) and Photochemical Oxidation (PO) were calculated 0.00002-0.00004 kg CFC11 eq and 0.145-0.174 kg C 2 H 4 eq for wheat production (irrigated and reainfed), respectively. The results showed that the main hotspots for irrigated and rainfed wheat production were chemical fertilizers and diesel fuel. Based on the results, it is suggested to use more intensive cropping systems (such as solar greenhouse) to decrease the intensity of input energy and increase the output level of productions with minimum environmental pollutions.