Abstract: In order to study the effect of controlled drainage on soil moisture, we carried out experiments of controlled drainage and free drainage for comparison in the land for growing field crops at Drainage and Irrigation Station in Jingzhou, Hubei province, 2010. We observed the soil water content in the whole cotton growth period and analysed the coefficient of soil water content variation. Results showed that controlled drainage had an obvious effect on soil water content in the whole growth period by retaining moisture and reducing the fluctuation of soil water content especially after rainfall, but the relation between soil water content and controlled water table was not definite.

Key words: controlled drainage, soil water content, coefficient of variation