Characteristics of evapotranspiration and energy budget of soybean field in the Sanjiang Plain
三江平原大豆田蒸散特征及能量平衡研究

The evapotranspiration, water use efficiency, radiatio n budget and energy balance of soybean field in the Sanjiang Plain are analyzed in this paper. The results show that the evapotranspiration capabilities of farmla nd are equal to precipitation during the crop growth season, the change of soybe an field evapotranspiration is similar to the change of leaf area index. The ratio s of net radiations to total radiation are different in different soybean growth stages and the value is 50% in the sowing and seedling stage, increases to 60% in the florescence and bear pods, finally decreases to 55%in the milking and har v esting time. The energy balance of soybean field has daily change and seasonal v ariation, the latent heat consumes 90% of net radiation, the sensible heat and t he soil heat flux are very small during the soybean growth season, and the value s respectively are below 1.5% and 10%.