How does soil water content influence crop water use?
As soil dries, the stress that plants experience as water is removed from the soil gradually increases. At field capacity (maximum water content), plants use water at the maximum rate determined by climatic conditions at the time. As the soil water content drops below field capacity, and progressively becomes less and less, plants use less and less water. Eventually, the tension with which water is held in the soil becomes sufficiently great that water can no longer be removed by the plant, and the plant experiences stress. Different crops have different water requirements and respond differently to water stress – both the magnitude of the stress and the timing of the stress relative to the plant growth process. The range of water use for crops also varies from one area to another (Iowa State University Extension).
