Basics Of Soil Science

(a) Gravitational water: Water in soil that moves downward due to gravity, filling large pores after heavy rain or irrigation, unavailable to plants as it drains quickly. (b) Hygroscopic water: Water tightly bound to soil particles by adsorption, held at high negative matric potential (e.g., -31 bars), unavailable to plants. (c) Combined water: Water chemically bound in soil minerals (e.g., hydrated salts like gypsum, CaSO H O), unavailable to plants as it’s part of the crystal structure. (d) Capillary water: Water held in soil micropores by capillary forces, available to plants as it’s retained against gravity but accessible to roots.