Physical properties

First Part.

      (1)        Soil water

                               

Hygroscopic water- Reaming water strongly adheres to soil particles. Roots of plants can’t absorb this water.

Capillary water- Water retains between pore spaces in soil. Pore spaces of soil aren’t still saturated totally. This water is available for roots.

Gravitational water-Water drains through the soil because pore spaces of soil are totally saturated by water.

Amount of water in soil vary as follow: Gravitational water> capillary water> hygroscopic water

Field capacity–water held in the soil after complete wetting followed by free drainage

Wilting point–water that is held too tightly for plants to absorb the difference between field capacity and wilting point 100% of field capacity –optimal 75% of field capacity –enough for irrigation 50% or less of field capacity - Doesn’t enough for irrigation. Soil water content can be measured by using two methods.

 (1)         Soil water content (by weight)

Ɵm = Mw / Ms

Ɵm- soil water content

Mw- a mass of water evaporated (≥24hours @105ºC)

 Ms-mass of dry soil

(2)Soil water content (By volumetric)

Ɵv = Vw / Vs

Ɵv- volumetric water content

Vw-volume of water

 Vs-volume of soil sample