| Under field conditions, the effects of application level of nitrogen on grain filling characteristics and spike traits of winter wheat were studied.The grain filling process of two wheat cultivars with different spike-types were modeled with Cubic, Quadratic and Logistic equation,in which all the R2 values were significant, and the difference among the R2 values was also significant. There was a significant correlation between grain weight and W,S,Se and Ws, so it was a practicable and effective way of increasing grain weight to raise the filling period, the effective filling period and the grain increase during the effective filling period.The effect of N rates on 1000-kernal weight of the two spike-type cultivars was significantly different. The yields of the two cultivars were the highest when N rate was 225 kg/hm2, but the yield of Yumai 49 was higher than that of Yumai 66. |