Hygroscopic water is also called:

• Free water or Gravitational water:
-The water that can flow freely under gravity and is available for drainage is called free water.

• Capillary water:
-The water retained by soil with its moisture-holding capacity under tension (Surface tension) is called capillary water.
-Plants use this water for their growth.

• Hygroscopic water:
-The water that is sandwiched or adsorbed or tightly held between the colloidal soil particles is called hygroscopic water.
-This water is difficult to extract even by the plant as a force of attraction between soil and water may reach as high as 1000 atm.

• Chemically combined water:
-After all the hygroscopic water is gone by heating soil to 150 o C, the remained water in the soil is called chemically combined water.
-It is irrelevant to extract water from this soil as it changes the physical and chemical properties of the soil.