The infiltration rate of a soil is the velocity at which water can seep into the soil. It is commonly measured by the depth (in mm) of the water layer that the soil can absorb in an hour. An infiltration rate of 15 mm/hour means that a water layer of 15 mm on the surface of the soil, will take one hour to infiltrate into the soil (Tidemann 1996).

Infiltration is the process when rain or irrigation water which is supplied to a field seeps into a soil (Tidemann 1996).

Determining factors

The infiltration rate depends on different factors. Soil texture is an important determining factor. In a sandy soil, the infiltration rate is higher than in a silty soil, for example. Further factors influencing the infiltration rate are

• soil structure;
• humus content;
• soil moisture;
• soil depth;
• soil surface roughness.

Values for infiltration rates

The range of possible values for infiltration rates are classified by Tidemann (1996) as follows

• low infiltration rate: < 15 mm / hour;
• medium infiltration rate: 15 to 50 mm / hour;
• high infiltration rate: > 50 mm / hour.