Effect of Two Irrigation Regimes on Crop Water Stress Index and Yield and Yield Components of Triticale (X Triticosecale Wittmack) Cultivars

A field experiment was conducted to evaluate the crop water stress index (CWSI), grain yield and canopy temperature of triticale under two irrigation regimes at Research Station of College of Agriculture and Natural Resources of Darab, Shiraz University, in 2013. A split plot design was used with three triticale cultivars (Sanabad, ET-83-3, and ET-84-5), as sub-plots and four levels of irrigation  regimes including well watered, cutting off irrigation at flowering, milk development, and dough development stages as main plots replicated three times. Results showed that Sanabad (6.31 °C) and ET-83-3 (6.89 °C ) cultivars  had the higher canopy-air temperature differences, while in ET-84-5 this difference reached to 2.66 °C. In all cultivars, high amount of variation (0.18 to 0.91) was observed for monthly CWSI and decreased by cutting off irrigation from flowering to dough development. Under cutting off irrigation at flowering, ET-83-3 with 0.67 had the highest mean seasonal CWSI, while in ET-84-5 reached to 0.50.  In cutting off irrigation at flowering, the highest triticale grain yield was obtained in Et-84-5 (354.3 g) and it might be attributed to higher grain number per spike and spike number per square meter compared to Sanabad and ET-83-3. Polynomial regression showed that with increasing CWSI, triticale grain yield decreased and the slope of regression between 237 to 284 g/m2 grain yield was more than the other spots (R2=0.79). The highest grain yield (476.2 g/m2) was obtained in ET-84-5 under well watered and CWSI in this cultivar ranged from 0.18 to 0.33. By cutting off irrigation at flowering and increasing CWSI compared to cutting off irrigation at milk and dough development stages, grain yield decreased especially in Sanabad and ET-83-3, significantly. Overall, ET-84-5 with lower canopy and air temperature differences (Tc-Ta) and mean CWSI, had better performance when exposed to cutting off irrigation.