The B horizon of a soil; the zone where iron oxides and clay minerals accumulate. The A horizon of a soil; most fertile layer of soil where humus, plant roots, and living organisms are found.

A soil profile is a vertical section of soil like the diagram above. It allows you to examine the structure of soil. A soil profile is divided into layers called horizons. Most important for plant growth, the A and B horizons are the top two layers of the soil.

The water holding capacity is highest in sandy soil clay soil loamy soil or mixture of sand and Loom, so it is highest in clay soil.

Soils with a percolation rate faster than five minutes per inch are acceptable if a 12-inch thick loamy sand soil liner with a percolation rate of 15 to 20 minutes per inch is installed in the trench or bed. The trench or bed is then sized based on this soil liner percolation rate.

Note: Percolation rate means the rate by which water passes down slowly into the soil. But water does not percolate at the same rate in all types of soils. Sandy soil allows maximum percolation of water and clay soil allows minimum percolation of water.

The soil percolation rate indicates how quickly water moves through soil and helps evaluate the ability of the soil to absorb and treat effluent — wastewater that has received preliminary treatment in a septic tank. The percolation rate is measured in minutes per inch (mpi).

Percolation rate (ml/min) = amount of water (ml) / percolation time (min). For example, If 200 ml of water is percolated through the soil sample in 40 min.

Examples. Coffee percolation (see Fig. 1), where the solvent is water, the permeable substance is the coffee grounds, and the soluble constituents are the chemical compounds that give coffee its color, taste, and aroma. Movement of weathered material down on a slope under the earth’s surface.

PERMEABILITY= How WELL water can flow through soil particles. PERCOLATION= The RATE at which water can travel through the soil particles.