小麦吸氮动态与生长动态的关系

试验在扬州市郊区沿江高沙土上进行。对少(免)耕小麦吸氮动态及生长动态进行数学模拟结果表明,江苏沿江地区扬麦5号小麦的吸氮速率最大期和生长速率最大期分别在叶龄余数2.7～0.2和孕穗末至始穗之间。乳熟以后,植株累积吸氮量常因氮素损失而减少,以致吸氮速率可能出现负值。吸氮速率最大期的累积氮量、全生育期的吸氮总量、生长速率最大期的累积生物量以及生长最大速率均与产量密切相关,其中生长速率最大期的累积生物量是小麦生长最重要的指标。拔节肥的作用主要在于减缓吸氮速率最大期以后吸氮速率的下降程度,防止早衰,以促使生长速率最大期的累积生物量能达到一定的高产指标。吸氮速率最大期的累积生物量与高产小麦同期累积生物量指标的差数,是确定拔节肥施氮量的主要依据之一。高产小麦吸氮速率最大期(叶龄余数2.1左右)是追施拔节肥的最适时期。

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.