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Field evapotranspiration composition of crop transpiration and soil evaporation, crop transpiration an important part in the life rhythm of both crops, soil - plant - atmosphere system (SPAC) are important components of the water cycle and water balance. The field evapotranspiration research farmland water resources assessment, crop - water relations, irrigation schemes, making the premise of the basic content, have an important role in agricultural production. In this thesis, the weighing lysimeter and plant sap flow meter real-time monitoring and analysis of the variation characteristics of transpiration in the late spring corn field evapotranspiration process of change and corn, the main results obtained are as follows: 1. Rainfed spring maize field evapotranspiration changed. Spring maize growth period, the date of filling stage evapotranspiration highest 4.26mm / d, about 4.5 times the seedling stage; June, July and August high evapotranspiration during the trial period \fluctuation peak on the low evapotranspiration period; daily evapotranspiration curve reflects the role of precipitation soil moisture conditions improve conditions Evapotranspiration of performance under the premise of follow-cyclical, double crop growth stages and meteorological factors; when evapotranspiration affected. Under the test conditions, the yield of spring corn initial stage and the development stage of actual evapotranspiration ET lower than the reference crop evapotranspiration ET0 ET0 higher than in the mid-term and final stage ET. In the initial developmental stages of growth of spring maize, actual evapotranspiration to soil evaporation; in the final, farmland evapotranspiration to crop transpiration increases rapidly and reached the highest ET gradually approaches the ET0. spring maize growing in the late transpiration change the order of the dough stage> the grouting of> tasselling, silking> maturity. The photosynthesis system measured the corn leaf net photosynthetic rate and transpiration rate reached the highest water use efficiency both in the filling stage tasseling silking highest. Under different weather conditions, corn transpiration change significantly. Sunny transpiration rate of a single peak curve; cloudy weather conditions, transpiration rate showed a single peak curve, but the transpiration rate is much smaller than a sunny day; rainy weather conditions, the the transpiration rate change unstable. At the same time experimental results show that the plant transpiration by the effective solar radiation, air temperature, relative humidity, wind speed, atmospheric pressure and other environmental factors, including effective solar radiation, relative humidity and temperature affect transpiration change the dominant factor. 4 spring maize growth in the latter part of daily evapotranspiration and transpiration date trends, farmland evapotranspiration main crop transpiration, evapotranspiration ratio of transpiration accounted for more than 70%. From the late growth stage, water consumption by transpiration 75.7% of the total evapotranspiration, soil evaporation accounted for 24.3%. During the day, evapotranspiration and daily transpiration between the same trend, the coexistence of linear positive correlation, regression equation: y = 1.1869x 0.4095, correlation coefficient of 0.6419.
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