How does soil texture affect soil water potential as a soil

How does soil texture affect soil water potential as a soil dries? Would a sandy or clayey soil contain more water when a plant is at the permanent wilting point? Explain the cation exchange capacity in this process and its importance.

Solution

ans.

total water potential = matric potential + gravitational potential + pressure potential

Soil water potential is the amount of water required to move water from the soil.Water moves from region of higher conc to region of lower conc

Since the soil texture changes as the soil dries , the pore sizes decreases and soil becomes cracked and the soil water potential decreases.

Texture

% Water

Field Capacity

sand

6%

-1/3 bar

loam

15%

-1/3 bar

clay

24%

-1/3 bar

clayey soil contains more water than sandy soil at permanent wilting point as claey soil accumulate more water as compared to the sandy soil.

Cation exchange capacity is the ability of soil to hold exchangeable cations

Sandy soils rely heavily on the high Cation exchange capacityof organic matter for the retention of nutrients in the topsoil.