Fig. 2.12 Details of idealized WRCC

The slope of WRCC is termed as specific capacity or differential water capacity and represented by C(θ) =(dθ/dψ). This is an important property describing water storage and water availability to plants. As C(θ) is more, water drained out or water availability from that soil is more. For a particular increase in ψ, the coarse grained soil releases more water than fine grained soil.
           A large variety of instruments are available for measuring ψ_m or ψ in the field or in the laboratory, either directly or indirectly. A summary of various instruments used for measuring soil suction is presented in Table 2.5. Each of these measurement techniques has its own limitations and capabilities, and active research is ongoing for further improvement.