Q172
General ScienceBiology
Water available for plants within the soil is
- a.Hygroscopic water
- b.Capillary water
- c.Mineral water
- d.Chemically bound water
Answer: (B) Capillary water
Soil water is classed as gravitational, capillary and hygroscopic. Capillary water, held in the fine pores between soil particles by surface tension, is the water that roots can absorb, so it is the 'available water' (roughly the water between field capacity and the permanent wilting point). Gravitational water drains down quickly to the water table; hygroscopic water forms a thin film held too tightly on soil particles to be absorbed; and chemically combined water is part of the mineral crystals. 'Mineral water' is not a category of soil water. Loam holds the most available water; sand drains too fast and clay holds much of its water too tightly.