Impacts of precipitation on wheat yield during growth period

In order to explore the mechanism and regular pattern of precipitation on wheat yield, the impacts of precipitation from 1971 to 2005 on wheat yield during its growth period were imitated using APSIM model and quadratic polynomial stepwise regression analyzed in Dingxi City, Gansu province. The results showed that wheat production was not only affected by total annual precipitation, but also the variations of growth period precipitation. The most effective precipitation period was seedling stage and followed by jointing stage, carry flag stage, heading stage, filling stage and flowering stage. The correlation between precipitation and wheat yield during seedling stage and jointing stage showed downward opening parabola. Effects of precipitation in seedling stage and jointing stage were 6.6 and 3.7 times of precipitation in carry flag stage, respectively. Effects of precipitation in heading stage, carry flag stage, flowering stage and filling stage on wheat yield showed secondary superposition incremental trends during the studied area. The precipitation in seedling and elongation stage was one of main limit factors of wheat yield in this studied area.