Comparative study of crop evapotranspiration measured by Bowen ratio and lysimeter

Crop evapotranspiration provides scientific basis for rational irrigation and water resources allocation. In order to estimate the crop evapotranspiration accurately, two evapotranspiration variables of winter wheat were analyzed. One was estimated by Bowen ratio-energy balance equation (ET_b), the other was measured by lysimeter (ET_l). The results indicated that the variations of ET_b were almost the same as those of ET_l. Variations of ET_b and ET_l were single peak curves. Their values were bigger at noon, and smaller in the morning and evening, and negative at night. The diurnal variation of ET_b was smaller than that of ET_l. Their diurnal variations were weakly negatively correlated with wind speed if the wind speed was small, but if the wind speed was big, the trend that ET_l decreases with the increase of wind speed was obvious. The ET_b was highly related to net solar radiation, while ET_l was not obviously related to net solar radiation. Crop evapotranspiration estimated by Bowen ratio represents the diurnal variation more steadily.