Irrigation water quantity and quality limitation is the main problem of agricultural development in the research area (Rafsanjan pistachio orchards in Iran). Optimization of the irrigation system is one of the most important factors to enhance water use efficiency in this region. This research project was designed to compare the applicability of two different types of irrigation, including traditionally used surface irrigation and a simple and relatively cheap subsurface drip irrigation (using a perforated pipe covered with plastic cloth). For this purpose two plots, each containing 39 pistachio trees and 720 m 2 in area, were selected in an orchard and were both irrigated using an exactly equal quantity and quality of water for 3 years. At the end of the second year the yield in the plots was harvested separately and compared. The ratio of the weight of fresh and also dried crop in the subsurface irrigation plot to those of surface irrigation plot was respectively 1.895 and 2 for the second year, and 2.17 and 2.12 for the third year. Another parameter measured for the trees of the two plots was annual shoot growth. The value of the plot growth index (PGI) in the surface irrigation plot was calculated as 2238 cm, whereas in the subsurface irrigation plot it was 4580 cm. In addition, the dried weight of weed grown in the surface irrigation plot was 82 kg but was only 21 kg in the subsurface irrigation plot. These results show the considerable difference in efficiency of the two irrigation systems, and relatively higher preference for a subsurface system over the traditionally used surface method.

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