Responses of unheated greenhouse grown green bean to buried drip tape placement depth and watering levels

Subsurface Drip Irrigation (SDI) is a professional water distribution system for improved crop water use and conserving water. Selecting drip tape installation depths for different crops is the most critical decision with these systems. Hence, the aim of this research was to examine the effects of different SDI depths and water amounts on the yield components and water use characteristics of green bean crop under unheated greenhouse conditions during two crop-growing cycles. Three irrigation methods [Traditional Drip Irrigation (DI), SDI at 10 cm soil depth (SDI10) and SDI at 20 cm soil depth (SDI20)] and six irrigation water levels (I) based on crop-pan coefficients (I20:Kcp = 0.20, I40:Kcp = 0.40, I60:Kcp = 0.60, I80:Kcp = 0.80, I100:Kcp = 1.00 and I120:Kcp = 1.20) were evaluated. In each growing cycle, adequately watered crops (I100) were accepted as control. The seasonal evapotranspiration changed from 235 to 374 mm in autumn and from 270 to 566 mm in spring season. Different placement depths of drip tape had significant effects on green bean yields in spring growing cycle. Maximum yield (5.97 kg m−2) was obtained in SDI10 irrigation method. Irrigation water levels also significantly (p < 0.001) affected green bean yield in both growing cycles. The highest yield (1.66 kg m−2 in autumn and 6.81 kg m−2 in spring) was obtained in I100 treatment. SDI techniques improved Water Use Efficiency (WUE) and Irrigation Water Use Efficiency (IWUE). The values of WUE and IWUE increased as the watering level was reduced. Maximum yield response factor in DI method in autumn and spring seasons (Ky) was found as 0.96 and 1.66, respectively. General evaluation of the water management, crop yield components and growth variables showed that the SDI10I100 treatment appears to be the most favorable irrigation practice for the green bean grown under greenhouse conditions. Water savings of up to 13% of seasonal irrigation water could be achieved using SDI method.