The water use in a conventionally-managed cotton field was observed in an and region in Xinjiang Uygur Autonomous Region, P. R. China. Evapotranspiration and transpiration of the cotton community, evaporation from the soil surface under the cotton canopy and soil moisture were monitored.
Evaporation from the soil surface, i. e. loss of water that did not contribute to the cotton production, was substantial after irrigation. The empirically-determined interval of irrigation was too short and irrigation tended to be applied even when soil moisture was available. The amount of water for one irrigation was larger than necessary for crop production, and a considerable amount of water was lost by downward percolation. A water balance calculation was undertaken for determining the suitable amount of water and interval of irrigation.