Biomass accumulation and radiation use efficiency of winter wheat under deficit irrigation regimes

A field experiment was conducted to study the effects of deficit irrigation regimes on the photosynthetic active radiation (PAR), biomass accumulation, grain yield, and radiation use efficiency (RUE) of winter wheat during the years 2006-2007 and 2007-2008. Wheat was irrigated 1, 2 or 3 times at sowing, jointing, or heading stages. The total irrigation water was all controlled at 120 mm. The results indicate that irrigation 2 or 3 times could help to increase the PAR capture ratio in the later growing season of winter wheat; this result was mainly due to the changes in the vertical distributions of leaf area index (LAI) and a significant increase of the LAI at 0-20 cm above the ground surface. Compared with irrigation only once during the growing season, irrigation 2 times significantly increased aboveground dry matter at maturity; irrigation at sowing and heading or jointing and heading stages significantly improved the grain yield, and irrigation at jointing and heading stages provided the highest RUE (0.56 g/mol). Combining the grain yield and RUE, it can be concluded that irrigation at jointing and heading stages has higher grain yield and RUE, which will offer a sound measurement for developing deficit irrigation regimes in North China