| ET and crop coefficients are important elements for estimating irrigation waterrequirements and in water resources management. It is of great significance in theagricultural production. In this paper, the calculation of crop evapotranspiration （ETc）and crop coefficient （Kc） of maize was conducted with data obtained throughAutomatic Weather Station System and Dynamax Sap Flow Measuring System, Themain results are as follows:1. The results of ETothat were determined by four different P-M methods werealmost similar in2011. FAO56-24h is660.07mm and have well linear correlation withthe observed ETc, following by PM56-1h ASCE-24h, ASCE-1h. Reference cropevapotranspiration has positive correlation with radiation （Rn）, VPD, temperature （T）and wind speed. Rnis the most influential factor, following by VPD. A negativerelative relationship is found with the relative humidity.2. ETocould be calculated with a simple method by Rnand VPD.3. The change of maize sap flow has single-peak curve in sunny day, single-peakor irregular multi-peak curve in windy day and multi-peak curve in cloudy and rainyday. In the three different weather conditions, Rnhas the processing with the sap flow.The water consumption of maize was declined in the order of sunny days> windydays> cloudy days> rainy days, with the mean value being3.49mm/d,2.13mm/d,1.49mm/d.4. In the medium and the late growth season, the change of ETcranked in thedescending order of wax-maturity stage, grain-filling stage, tassel-silk stage andmature stage. Wax-maturity stage is as much as grain-filling stage.5. Under the climate conditions of the city of Yulin, if variety is no changes, thesingle crop coefficient of maize is Kcini=0.34，Kcmid=1.23, Kcend=0.59.6. The calculated ET is similar to observed ETcand the local corn crop waterrequirement can be calculated by the single crop coefficient. The crop water requirement of maize is599.68（mm） in the whole growth season of2011and is486.84（mm） in the whole growth season of2012. |
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