Evaluation of crop water stress index (CWSI) for red pepper with drip and furrow irrigation under varying irrigation regimes

•Full irrigation with drip system produces higher red pepper yields compared to deficit irrigation.•Water stress results in higher WUE.•Average threshold crop water stress index (CWSI) values for irrigation scheduling are 0.26 for drip and 0.37 for furrow system.•Water stress increases the disease incidence significantly. An experiment was conducted to determine the effect of water stress on yield and various physiological parameters including crop water stress index for drip and furrow irrigated processing red pepper in the 2010–2011 growing seasons in the Mediterranean region of Turkey. Drip treatments consisted of full irrigation (DFI), deficit irrigation DDI-75 and DDI-50 which received 75 and 50% of DFI, respectively. D-PRD-50 and DF-PRD-50 alternative and fixed partial root drying, received 50% of DFI. Furrow treatments consisted of full irrigation (FFI), fixed alternative furrow (FAF-50) and PRD furrow (FPRD-50). FAF-50 and FPRD-50 received 50% of water applied to FFI. In FAF-50 the same furrows were irrigated while FPRD-50 was irrigated in alternate furrows. The experimental design was randomized blocks with four replications for drip and furrow treatments. Both irrigation methods and levels had a significant effect on the total yield of red pepper. Drip produced higher red pepper yields than furrow. The highest yield was obtained from the DFI treatment followed by DDI-75, DDI-50 and DF-PRD-50 treatments. Although, D-PRD-50, DF-PRD-50 and DDI-50 received the same amount of water, D-PRD-50 had a higher yield. In furrow, FFI resulted in the highest yield followed by FPRD-50 and FAF-50. The lowest water use efficiency (WUE) was obtained from the DFI while the highest WUE was found in DPRD-50 in drip system. The lowest WUE was found in FFI, and the highest WUE was in FPRD-50 treatment under furrow. The threshold crop water stress index (CWSI) was 0.26 for drip and 0.38 for furrow prior to irrigation. There was a significant relation between yield and CWSI. A high correlation was found between CWSI and leaf area index. The results revealed that DFI for the drip and FFI for the furrow were recommended. Under water scarcity conditions, DDI-75 and D-PRD-50 treatments can be recommended.