Effective quantitative and qualitative management of water for irrigation is crucial in many regions and the use of reclaimed water is a possible solution. Quantifying the impact of the use of such water is thus important. Using life cycle assessment methodology, this study analyzes the impact of water reuse irrigation and farmers' practices in greenhouse cucumber production. Three scenarios concerned sources of water for irrigation and agricultural practices: the first scenario used surface water including reclaimed water, the second used groundwater. The third scenario resembled the first but also accounted for fertilizer application based on theoretical cucumber requirements. The third scenario showed 35% less fertilizer is required than the quantities farmers actually use. Our results show that the higher environmental impact of irrigation using reclaimed water than using groundwater is mainly due to the over-fertilization. Comparison of the first and third scenarios also showed that the reduction in the environmental impact under the third scenario was significant. We conclude that LCA is a useful tool to compare the impacts of different water sources and farmers' irrigation/fertilization management practices, and in particular, that the quantity of nutrients in reclaimed water should be deducted from the actual amount applied by the farmers.