Physiological responses of wheat (Triticum aestivum L.) to deficit irrigation and sowing density

To evaluate the effect of sowing density (300, 400, 500, 600 and 700 plants/m2) on growth of wheat under deficit irrigation (100, 75 and 50% crop water requirement, I100, I75 and I50), an experiment was carried out during 2009 and 2010. In both years, deficit irrigation resulted in considerable reduction in yield, yield components, leaf area index (LAI) and leaf water potential (Ψw). In contrast, the canopy temperature (CT) significantly increased under deficit irrigation. Furthermore, increasing of sowing density from 300 to 600 plants/m2 resulted in significant increase in grain yield under I100 and I75. Maximum grain yield as 525.9 and 564.2 g/m2 was obtained in the first and second year, respectively in sowing density of 600 plants/m2 and I100. This sowing density was also the proper density in I75 and I50 irrigation regimes. Increasing of sowing density reduced 1000-grain weight and grain number per spike and increased spike number per square meter. In the first year, increasing of sowing density from 300 to 600 plants/m2 caused a significant increase in LAI in all irrigation regimes, while in the second year, maximum LAI was observed in 700 plants/m2 sowing density. It was found that increasing of sowing density significantly reduced the Ψw and the CT in both well-watered and deficit irrigation. In conclusion, the results suggest that 600 plants/m2 would be the optimal sowing density under different water conditions. Alleviation of water stress by the increasing sowing density was found to be associated partly with enhanced LAI and reduced CT.