Evaluation of crop water stress index and leaf water potential for deficit irrigation management of sprinkler-irrigated wheat

This study evaluated crop water stress index (CWSI) and midday flag leaf water potential (Psi(1)) on wheat (Triticum aestivum L. Adana 99) under the three different supplemental and conventional irrigation strategies using sprinkler line-source system during 2014 and 2015 in Adana, Turkey. The irrigation strategies were as follows: conventional irrigation (CI), supplemental irrigation (SI) during flowering (SIF), SI during grain filling (SIG), SI both during flowering and grain filling (SIFG). These strategies were tested under four irrigation levels 100, 75, 50, 25% and rain-fed. The CI100 treatment achieved the highest grain yield in both seasons, followed by CI75 and SIFG(100). The CI75 had the greatest water use efficiency of 1.20 kg m(-3), and SIF25 resulted in the lowest WUE. Grain yield and available soil water correlated linearly to CWSI. These relations could be employed in predicting the yield response to water stress. A higher grain yield was obtained when irrigation was applied at CWSI values less than 0.26, suggestingCWSI as a good indicator to improve irrigation timing for wheat. Prolonged drought in early grain filling stage led to a decline in Psi(1) in the advanced growth stage which in turn reduced grain yield. Significant correlations between Psi(1) and grain yield and CWSI were obtained, which could be useful in improving wheat irrigation water management. CI100 is recommended when there is no water shortage; however, under water scarcity conditions CI75, SIFG(100) and SIFG(75), with higher WUE and relatively higher yields, are recommended.