Evaluation of rainwater harvesting systems performance in runoff production and in grape yields

Low rainfall and its poor distribution in the West Azerbaijan province have hampered agricultural production in dry-land. One of the important solutions in this regard is converting rainfall into runoff. In this study, a field experiment in Khoshalan village of Urmia on grapes in rainfed conditions with supplementary irrigation and rainwater harvesting was carried out in a split-plot design based on randomized complete blocks for six years from 2000 to 2006. The first four years were for seedlings of plants, and recording of yield was possible in 2005 and 2006. The three factors studied include fertilizer application factor in 30 and 70% of the usual recommendation for irrigated cultivation, watershed area factor in areas of 12, 20, and 30 m2, and runoff surface status factor including normal traffic, plastic cover, and paving stones. In this study, the benefit is calculated based on the cost and income of 2019. The results showed that with increasing fertilizer consumption, yield decreased from 1755 to 1461 kg/ha, and benefit decreased from 81.2 to 46 million rials. This result indicates that under semi-dry conditions, fertilizer, cannot be consumed in large quantities. With decreasing watershed area, yield and benefit increased from 1018 to 2451 kg/ha and from 6.2 to 148 million rials, respectively. Plastic with 2208 kg/ha and 113.6 million rials had an increase in yield and profit of 54 and 86% compared to the control. Also, paving stones compared to the control, experienced 1 and 49% yield reduction, and profit respectively. According to the results of this study, an area of 12 m2, with plastic cover with 70% of the usual fertilizer recommendation for irrigated cultivation, increases the yield of rainfed grapes.