Classification of soil water

i. Gravitational water

Water containing in macropores and drains out freely under the influence of gravity is called gravity is called gravitational water. It is the water in excess of hygroscopic and capillary water. Most of the gravitational water is not available to plants for the use because it drains out rapidly from the root zones.

ii. Capillary water

Water retaining in micropores of soil after the drained off of gravitational water is known as capillary water, which is held in the capillary pores of soil by surface tension. It is held in soil against gravitational force and thus water is the principal source of water for plant growth.

iii. Hygroscopic water

Water adsorbed by dry soil particles from the atmosphere and is held as a very thin film on the surface of soil particle due to adhesive force. Generally, hygroscopic water is referred as unavailable to plant.