Effects of surface and subsurface drip irrigation on soil water moisture variation and soil-water tension

This study was carried out to determine irrigation time and the treshold value of soil-water tension using tensiometers placed into the different soil depths at surface drip (SDI) and subsurface drip irrigation (SSDI) systems for cotton. The irrigation was scheduled according to the real water evapotranspiration of plants based on FAO-Penman-Monteith (PM) method. The experiment was performed in cotton growing seasons of 2016 and 2017. The values of tension were read for each 5 days before and after irrigation at the tensiometers placed into the soil depth of 15 and 45 cm for SDI and SSDI placed into the soil depth of 40 cm. The values of tensiometers could be considered to be 55 and 47 cb in the soil depths of 15 and 45 cm for irrigation time and SDI, respectively. In SSDI, the irrigation time should be considered to be 52 and 45 cb of tensiometer readings for the soil depths of 15 and 45 cm, respectively. In addition, management allowed deficit in both drip irrigation systems, SDI and SSDI, was determined to be 40 %