Management of supplemental and deficit irrigation for wheat production under the Mediterranean climatic conditions

This study evaluated the effect of three different supplemental and conventional irrigation strategies on crop water stress index (CWSI), midday flag leaf water potential Ψl, leaf stomatal conductance gs, chlorophyll content (SPAD), economical parameters, yield, yield components and quality of wheat (Triticum aestivum L. Adana 99) using sprinkler line-source system during 2014 and 2015 seasons in the Mediterranean region. The irrigations strategies considered were: (1) conventional irrigation (CI); (2) supplemental irrigation (SI) during flowering (SIF); (3) SI during grain filling (SIG); and (4) SI both during flowering and grain filling (SIFG). The above strategies were tested under four irrigation levels 100% (I1), 75% (I2), 50% (I3), 25% (I4) levels and rain-fed (I5) was also included in the study. Full conventional treatment achieved the highest yield and yield components and the deficit irrigation 75% had the greatest WUE. A higher grain yield was obtained when the irrigation was applied at CWSI values less than 0.26. The highest chlorophyll reading of CI100 was 17.8% greater than the lowest value in RF. The higher grain yield was achieved when the seasonal gs reached to 207.4 mmol/m2s in CI and to 169.21 mmol/m2s in SI. High determination coefficient between Ψl with grain yield was obtained which could be useful in improving the irrigation water management of winter wheat in the field. In relation to full SI strategies, SIFG and SIF generated the maximum (668.53 $/ha) and minimum net income (424.22 $/ha), respectively. The findings showed positive response between the quality parameters such as protein ratio, wet gluten content and sedimentation volume, and water stress depend on the applied water quantity and which stage the stress occurred.