Resource and energy use efficiency is one of the principal requirements of eco-efficient and sustainable agriculture. Seedy watermelon (Citrullus vulgaris; Joboni population) is irrigated by two methods including full and reduced irrigation systems in Iran. The objective of the present study was to compare seedy watermelon production in full (high input) and reduced (low input) irrigation systems in terms of irrigation water energy use efficiency (IWEUE), energy budget and economic analysis. Data were collected from 116 full irrigated and 93 reduced irrigated farms in northeast of Iran by using a face-toface questionnaire in 2011–2012. The results showed that the total energy consumed under high input systems was 25625.94 MJ ha−1, whereas under low input was 3129.3 MJ ha−1. IWEUE and all of the energy indexes were improved in the reduced irrigation system compared to the full condition. The direct and renewable energies in the reduced irrigation system were higher than full irrigation. The economical analysis indicated that higher return was gained by the full irrigation system due to higher yield compared to the reduced irrigation system. Human labor had the highest impact on seedy watermelon among the other inputs based on the Cobb–Douglas production function.

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