The Impact of Irrigation Frequency on Moisture and Salinity distributions under Subsurface Drip Irrigation (SDI) of Pistachio Orchards

Pistachio is a strategic product with high economic value in Iran، which is cultivated in arid regions withlimited water resources and poor water quality. Therefore، it is essential to use irrigation systems capable of yielding high irrigation efficiency along with effective management of soil water and salinity. In recent years، application of Subsurface Drip Irrigation (SDI) system has been widely accepted by manypistachio growers. Since، irrigation water is of poor quality in major pistachio plantations، utilization of this irrigation method will result in accumulation of salt in the vicinity of soil surface، hence a reduction in pistachio yield. In addition، appropriate irrigation interval for Pistachio orchards irrigated by SDI systems is unknown. A field experiment was conducted on 15-year old pistachio trees grown on loam silt soil and irrigated by subsurface drip irrigation with saline water (EC= 4. 2 dS/m) in a region under desert climate to investigate the effects of different irrigation regimes on the soil moisture and salinity distributions as well as pistachio yield. Two irrigation frequency treatments، namely I3 (Once every 3 days) and I14 (Once every 14 days)، replicated three times were applied to one hectare block of a farm in Sirjan. The results revealed that irrigation frequency had significant effects on the spatial distribution of soil water content within 0-100 cm depths with a higher soil water contentforI3. In contrast to I14، salt accumulation in the root zone for I3 was significantly (p<0. 05) low due to more water application. Pistachio yield for I3 and I14 was 3. 3 and 3. 7 kg/tree، respectively، indicating non significant difference. However، I3 showed marked enhancement in quality traits such as osteoporosis and smiling.