Field water surplus and deficit of major crops in dryland of northern China     

Received date: -- Foundation item: The national key research project: Field water balance  its regulation techniques  water potential productivity  its proper exploitation in typical dryland farming areas of northern China for the Ninth Five 《地理学报(英文版)》2000,(3)

1 IntroductionIn natural conditions, field water surplus or deficit is different between field water requirement and field water supply by nature. Field water requirement can be expressed either as potential field evapotranspiration or as crop water requirement. Potential field evapotranspiration is also called reference crop evapotranspiration which is defined as "the rate of evapotranspiration from an extensive surface of 8 to 15 cm tall, green grass cover of uniform height, actively growing…  相似文献