Yield response of wheat (Triticum aestivum L.) to deficit and regulated deficit irrigation under arid/semi-arid conditions

The objective of present research was to devise irrigation management techniques/practices for improved water use efficiency (WUE) and optimum wheat yield in water scarce conditions. Investigations with different irrigation regimes including: optimal, deficit (DI) and regulated deficit irrigation (RDI) at different crop growth stages were carried out on a deep loam soil for four crop seasons (2010-2014). The results showed that early vegetative/ crown root initiation followed by flowering/anthesis stage are highly sensitive to soil moisture stress and irrigation stress at these stages may reduce the yield from 12 to 20%. However, deficit applied at late vegetative/booting stage may provide an opportunity to save irrigation water with relatively lower grain yield reduction (9%), higher harvest index (2%) and grain based water use efficiency (WUE_g; 10%). The lower value of water production functions (k_{y =} 0.51) in the treatment with water stress at booting/late vegetative growth stage also indicated recovery of the crop from stress, exhibiting less than proportional reductions in yield with reduced water use. Regulated deficit irrigation (50% of the crop water requirement) at grain formation may result in comparatively lower yield reduction (-6%) relative to full irrigation skipped at booting, the reduction in harvest index (-3%) without any substantial increase in WUE_gmade it uneconomical.