夏玉米植株干物质、 氮磷钾养分积累速度和时间的动态分析

用Logistic方程及导出的速度方程， 探讨夏玉米植株干物质和氮、 磷、 钾养分积累速度与时间的数量关系，以期为动态过程分析提供一些新的资料。田间肥料试验结果表明，夏玉米植株干物质与养分积累速度的动态变化呈现不对称钟形曲线，根据曲线走向可将其划分为低速期（I）、快速期（II）和降速期（III）。三期时长各占夏玉米全生育期的1/3，但不同处理各期时长不同步。夏玉米出苗后30天左右内（I期）植株干物质和养分积累速度很低，与其后的II、 III期相比，速度相差一个数量级; 其后的II期速度最高，III期积累速度逐步下降，平均速度低于II期。植株干物质与养分的分期积累量取决于分期时长与速度两个参数。

Dynamic analysis of dry matter and NPK accumulation with time in summer maize

Logistic equation was used to simulate the temporal variation of dry matter and nutrients of the summer maize. The results show that the velocity of maize dry matter and stimulated nutrient contents versus time occur in asymmetry bell-shaped curves which can be divided into the slow (I),  quick (II) and declined growth periods (III). The duration for each period is about 1/3 of the total growth period with some fluctuate among different treatments. The cumulative speeds of the plant dry weight and NPK nutrients are very low within the first 30 days after germination (phrase I),  which are 1 to 2 orders of magnitude compared to phrase II and Ⅲ. The most quick accumulation is in the period II,  then slowdown at the period (Ⅲ). Generally speaking,  the cumulative amount of maize plant dry matter and nutrients in different stages depended on the staging time and speed.