Water movement in soil - Soil Essentials: Managing Your Farm's Primary Asset - page 133

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Water movement in soil
The study of water movement in soil is quite complicated, and soil scientists use a
number of terms to describe different aspects of water movement.
From a farmer's viewpoint it is the effects of water movement that will
determine land management issues. The important issues of water movement in
the soil are how much water is available to plants, the rate of nutrient leaching and
the extent of waterlogging.
Infiltration
This term describes the movement of water from the soil surface into the ground.
Water movement is greater when the soil surface has many open pores that water
can enter, and less when surface pores are clogged by compaction or siltation, or in
the case of nonwetting sands, by waxes repelling water.
Hydraulic conductivity
This term refers to how fast water is able to move through the soil. For example,
water can move easily and rapidly through a light sandy soil, but can have great
difficulty moving through dense clay, and cannot do so at anything like the same
rate as the sandy soil.
How fast water will move in a soil depends on how wet the soil is, so hydraulic
conductivity measurements are taken for dry soil being wet up, and for soil that is
fully wet. The terms used are: hydraulic conductivity unsaturated or hydraulic
conductivity saturated.