This study was conducted to assess the impact of cereals (wheat and barley) production on environment under rainfed and irrigated farming systems in northeast of Iran. Life cycle assessment (LCA) was used as a methodology to assess all environmental impacts of cereal grain production through accounting and appraising the resource consumption and emissions. The functional unit considered in this study was one ton grain yield production under different rates of nitrogen application. All associated impacts of different range of N fertilizer application were evaluated on the basis of the functional unit. In this study, three major impact categories considered were climate change, acidification, and eutrophication. In order to prepare final evaluation of all impacts on environment, the EcoX was determined. Results represented that, under low consumption of N fertilizer, the environmental impacts of both rainfed farming systems of wheat and barley was less than irrigated farming systems. Considering grain yield as response factor to different fertilizer application level, irrigated farming systems of wheat and barley with the range of 160–180 and[220 (Kg N ha-1) showed the maximum impact on environment. It seems LCA is an appropriate method to quantify the impact of utilized agricultural inputs and different managements on environment.

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