Soil Water Retention, Energy Concepts, Soil Water Potential, Retention Curves (pF) and Hysteresis

Statement (I) is true: Capacitance probes (high-frequency dielectric sensors, e.g., FDR) measure the apparent dielectric permittivity of the soil matrix, which is dominated by the high permittivity of water (~80) compared to mineral soil (~3-5) and air (~1), outputting instantaneous and precise numerical volumetric water content data.
Statement (II) is false: The tactile field method ('feel and appearance' / ribbon test) provides only qualitative or descriptive approximations (e.g., dry, moist, wet) rather than true numerical values; tactile sensations cannot yield objective numerical data.

The soil moisture content in increasing order from lowest to highest moisture is:

• Oven dry: $0\%$ moisture (suction $\approx 10,000\text{ bar}$ or $10^7\text{ cm}$ of water).
• Hygroscopic coefficient: moisture held at $31\text{ bar}$ tension.
• Permanent wilting point (PWP): moisture held at $15\text{ bar}$ tension.
• Field capacity: moisture held after free drainage ceases at $-0.1$ to $-0.33\text{ bar}$ tension.

The depth of irrigation water ($d_w$) required to raise the volumetric water content from $\theta_1$ to $\theta_2$ over a soil root zone depth $D$ is given by:

Given:
Root zone depth $D = 80\text{ cm}$
Initial volumetric water content $\theta_1 = 0.12$
Target volumetric water content $\theta_2 = 0.30$