Water Potential and Content (Guest Lecture) Flashcards
What are the 4 components of water potential?
Ψtotal = Ψg + Ψm + Ψo + Ψp
Gravity, matric, osmotic, pressure
Gravity pressure
Pulls water downward. Potential energy level of water in a given elevation will be higher than water at a lower elevation
Matric pressure
Water and its interaction with the surfaces around it, we have adhesion
Osmotic pressure
Water moves from dilute to more concentrated solutions to bring concentrations closer. Osmotic pressure is the minimum pressure to counter this movement
Pressure
Water flows to lose pressure which results from standing water above soil column
Soil water potential (SWP)
A measure of the potential energy per unit mass, volume, or weight of soil water, compared with that of pure, free, water
Hygroscopic water
Soil water held so firmly to soil particles by adsorptive forces that it cannot be extracted by organisms or move.
-3.1 bar or -3100 kPa
Saturation
Water drains or percolates readily by gravitational force, 0 bar and kPa and greater
What are the four soil water states?
Saturation, field capacity, wilting point, and hygroscopic
Available soil water
The amount of soil water in soil that is available for plants to use. Between field capacity and permanent wilting point.
Field capacity
Water content of a soil at upper limit of available water range. The operational definition of this is the amount of water remaining in soil after it was saturated and allowed to drain for 24 hours.
-0.1-0.3 bar OR -10 or -33 kPa
Permanent wilting point
Lower limit of available water range. When plants have removed all available water from soil, they wilt and do not recover
-15 bar or -1500 kPa
Influence of soil texture on plant available water
Coarse and fine-textured soil have the least amount of plant available water, while loamy textured soils have the highest PAW
