Effects of Surface and Subsurface Drip Irrigation Depths on the Yield Quantity and Quality of two Kabkab and Zahedi date palm varieties

Due to limitations in water resources scarcity, application of pressurized irrigation methods is inevitable for optimum use of water. This study was conducted in Behbahan Agricultural Research Station, during three cropping seasons (2013-2016). The statistical design was split plot with the design of randomized complete blocks  at three replications. The main plots were crop requirements at levels 75%  (SDI75), 100% (SDI100) and 125% (SDI125) of full irrigation for subsurface drip and 100 (SD100)  of full irrigation for surface drip irrigation and sub-plots were Kabkab and Zahedi date palm varieties. Results of combined variance analysis showed significant difference between the irrigation levels (1%) based on water use efficiency. According to the comparison of mean values, the highest yield with 8490.9 kg/ha belonged to SD100. Zahedi variety showed the highest water use efficiency of 0.686 kg/m3 under SDI75. Comparison of mean interactions showed that Zahedi variety had the highest water use efficiency with the amount of 0.744 kg/m3 compared to others treatments. SDI75 caused 2509.6, 5019.2 and 2630.3 m3/ha water saving in comparison to SDI100, SDI125 and SD100 Respectively. Combined analysis of variance showed that irrigation levels and cultivars had a significant effect on fruit moisture at 1% and 5% level, respectively, but the interaction effects were not significant. Comparison of mean values showed that SDI75 was superior and ranked first in the stiffness of tissue with 10.4 Newton/m2.