本文采用求极值的数学方法，分别考虑了一次、二次作物产量函数。提出了不同产量函数下适时作业期限合理延迟天数的确定方法，以及依据作物产量函数计算适时性损失的方法。

A method to determine the reasonable prolongation of the proper operating time is proposed in this paper using the differential method according to the linear and parabolic functions of crop yields.

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