The concept of crop water requirements is discussed, based on which the calculation modelof crop water requirements is established. In light with crop, soil and meteorological data. the cropwater requirements of major crops in sub-humid and send-arid dryland farming areas of northernChina. including wheat maize , cotton. millet, soybean, sweet potato and potato, are calculated, andthe patterns of crop water requirements of these crops are revealed and discussed in this paper.
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