Previous Year Question

The upper limit of soil water available to plants is generally considered to be the Field Capacity. Field Capacity is the stage at which excess gravitational water has drained from a previously saturated soil and the remaining water is retained in the soil.

In medium- to fine-textured soils, Field Capacity is generally associated with a matric potential of about −1/3 bar. Therefore, in this question, the upper limit of available soil water is 1/3 bar.

The lower limit of plant-available water is the Permanent Wilting Point (PWP), which is generally taken at about −15 bar. Thus, the water held between Field Capacity and Permanent Wilting Point constitutes the principal plant-available water.

Hence, the upper limit of available water is Field Capacity ≈ 1/3 bar, while the lower limit is approximately 15 bar.