Comparing Effects of Surface and Subsurface Drip Irrigation Systems on Growth and Yield on Mature Pistachio Trees

Unsustainable harvesting of agricultural water resources in the province of Kerman، has caused an annual average of one-meter drop in ground water levels. Surface irrigation methods in pistachio trees have low efficiency because of inherent characteristics and its incorrect application، as well as low access to water resource in pistachio regions. Therefore under the current critical condition، basic development of pressurized irrigation systems is an effective step to raise water use efficiency in the pistachio orchards. In this research، two irrigation systems including conventional surface drip irrigation and subsurface drip irrigation (SDI) with two drip line depths (30cm and 50cm) with three levels of water irrigation in each treatment، including 40%، 60% and 80% of irrigation requirement of pistachio in surface irrigation system (2932، 4398 and 5864 m3/ha. year respectively) for four years، was studied. Growth and yield factors، water use efficiency (WUE) and water and salinity distribution in root zone were measured. The results indicated that 30cm installation depth was the best treatment. Between irrigation systems، amounts of 60% and 80% irrigation requirement don''t have significant difference، but 40% irrigation requirement treatment، affected negatively on most of evaluated factors significantly. Therefore with regard to all evaluated factors in this research، subsurface drip irrigation with buried drip line at 30cm and 60% of irrigation requirement of pistachio in surface irrigation system، with water use efficiency of 0. 290kg/m3 and 25% water saving in comparison with surface drip irrigation system، was the best treatment and recommended.