Effect of Irrigation Scheduling Methods on Crop Yield and Water Use Efficiency of Wheat (Triticum aestivum)

Proper use of water resources in arid and semi-arid regions is important and vital. This study was conducted to evaluate the effect of irrigation scheduling by various methods on crop yield and water use efficiency (WUE) by wheat, and determining suitable irrigation-scheduling method for irrigation of wheat in Saeedabad, Tabriz. A field experiment was conducted with 10 irrigation treatments (I₁ to I₁₀) in randomized complete block design with 4 replications. The irrigation timing treatments comprised of two ratios of irrigation depth to evaporation from class A pan i.e. 0.8 (I₁) and 1.0 (I₂), two soil water potentials -40 (I₃) and -60 (I₄) kPa, two soil water contents i.e. 40% (I₅) and 60% (I₆) soil available water in root zone, two canopy temperatures i.e. stress degree days equal to 10 (I₇) and 12 (I₈), and irrigations at different physiological growth stages i.e. crown root initiation (CRI) + flowering (I₉) and CRI + late tillering + boot + milk stages (I₁₀). Results indicated that there was significant difference between treatments in biomass, grain yield, WUE, kernel weight, protein content and harvest index (HI). Among the treatments, I₂ had the maximum biomass, grain yield and kernel weight. I₉, I₁₀ and I₃ were the best treatments in WUE, seed protein content, and HI, respectively. Although the selection of the best irrigation scheduling method depends on water resources availability and existing facilities, in general, with due attention to irrigation frequencies and other consideration such as volume of applied water, grain yield, WUE, and simplicity of the method, we can recommend irrigation at –40 kPa soil water potential as a suitable method for timing of irrigation under this experimental condition.