Field Capacity:
- It is the amount of water that remains in the soil after all the excess water at saturation has been drained out.
- when sandy soils are allowed to drain for approximately 24 hours after saturation, field capacity is reached.
Saturation Capacity:
- It is the soil water content where all soil pores are filled with water and water readily percolates or drains out from the root zone by gravitational force.
- The metric suction at this condition is almost zero and it is equal to the free water surface.
Permanent Wilting Point:
- Permanent wilting point is considered as the lower limit of available soil moisture.
- At this stage, water is held tightly by the soil particles that the plant roots can no longer obtain enough water to satisfy the transpiration requirements; and remain wilted unless the moisture is replenished.
Readily available moisture:
- Readily available moisture is that portion of available moisture that can be most readily extracted by plants.
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In general, readily available moisture is approx 75 % of the available moisture.
Available moisture:
- The difference in water content of soil between field capacity and the permanent wilting point is called available moisture.
SC = Saturation capacity, FC = Field capacity, OMC = Optimum moisture content, PWP = Permanent welting point and UWP = Ultimate welting
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