The storage and the usable amount of soil water resource vary with the situations of meteorology, irrigation and crop growing.
土壤水储存量和土壤水可利用量随气象条件、灌溉以及作物状况不断变化；
2
Due to the spatiotemporal heterogeneity of meteorology, landform and physiognomy, different reference crop evapotranspiration methods have different applicability.