Preliminary Study on Evapotranspiration of Winter Wheat and Summer Maize Cropping System

A large-scale weighting lysimeter has been used for systematically exploring annual variation,periodic variation and daily variation of field evapotranspiration of winter wheat-summer maize cropping system. The relationship between evapotranspiration and the net radiation and other meteorological factors has been investigated by regression analysis. The results showed that,annual evapotranspiration distributed asymmetrically in four seasons and shaped M annually. Spring,summer,autumn,winter accounted for 44%,32%,17%,7%,respectively. Evapotranspiration peaked at jointing stage to heading stage of winter wheat and jointing stage to tasseling stage of summer maize. Those were water critical period of crop growth and supplementary irrigation critical periods. Daily evapotranspiration showed parabolic trends. Solar net radiation,air temperature and rainfall influenced evapotranspiration and followed by the same order as above,and solar net radiation and air temperature significantly affected evapotranspiration.