| The data of soil moisture in layer of 0～100 cm, precipitation and crop growing phrases in Zhengzhou and Nanyang were analyzed. The results showed that the variation of soil moisture with time could be divided into four periods: slow descending period, relative stable period, rapid descending period and increasing period. With regressive analysis, it was found that there were linear or parabola relations of between soil moisture in layer of 0～50 cm and layer of 0～100 cm when the rainfall was less than 10 mm, while there were hyperbola or conic hyperbolic relations between S50/S100 and precipitation (irrigation) when the rainfall (irrigation) was more than 10 mm. The regressive effect would be improved when rainfall (irrigation) was considered. But the regressive equations were different when the growing period or the soil type was different, reflecting the complexity of moisture relationship between the layers of 0～50 cm and 0～100 cm. |