RELATION BETWEEN DYNAMIC OF NITROGEN ABSORPTION AND GROWTH OF WHEAT

The mathematical simulation was employed in this paper in an atempt to describe the dy- namic states of nitrogen absorption and growth of wheat plant. Stages with highest N-absorption speed (Stage-1) and stages with highest growing speed (stage-2) in Yangmai. No. 5 wheat plant along the Yangtzc River were concentrated at leaf remainder 2.7 to 0.2, and the end of booting stage to the begin- ning of heading stage respectively. Bccause the amount of Nitrogen accumulated in the plant decreased af- ter dough stage due to the loss of nitrogen, the speed of nitrogen absorption probably became negtive. There was a significant correlation between yield and following faotors: the amount of nitrogen accumu- lated by the time of stage-1, the total amount of nitrogen accumulated in whole growing period of the plant and the biomass at stage-2 Among these factors, the biomass at stuges-2 was the most important in- dcx. The role of nitrogen applied at stem eongation stage was mainly to retard the process of the declinc of nitrogen absorbing speed after the stage-1 in case that the plant became senescent too carly and to impul the plant to match the index for high yield. The gap between the biomass at stage-1 and biomass at stage-2 was one of the main fundations in the determination of the amount of nitrogn applied at stem elongation stage. stage-1 of wheat plant with high yield (Leaf remainer about 2.1) was the most suitable time for appling stem elongation nitrogen.