Saturated hydraulic conductivity: Key to optimal drainage

The infiltration capacity of a soil refers to the flow velocity of the water flowing through it is also known as the hydraulic conductivity saturated. It is expressed as the height of water filtered per unit time (mm/h).

The term infiltration capacity describes the ability of a soil to drain water.

In order to measure the infiltration capacity of a soil we can perform a infiltration test. It is important to take the initial reading of the soil moisture as the infiltration rate will depend on these preconditions. It is normal for infiltration to be very fast at the beginning of the test if the soil is very dry, and will gradually decrease as the soil moisture increases. Once the capillary pores are filled with water, the gravitational forces cause a constant downward movement: we will then say that the saturated hydraulic conductivity.

Factors affecting the infiltration capacity of the soil are: timing of irrigation cycles, initial moisture content, hydraulic conductivity and surface conditions.

Depending on the soil textures, different infiltration values will be reached, and the curves will be different for heavy soils such as clay or light soils such as sandy soils. On newly constructed greens, values of 150mm/h are recommended (USGA), on stabilised greens, the Superior Sports Council recommends values above 100mm/h, and on sports surfaces as football pitches above 50mm/h.

Stainless Steel Double Ring Infiltrometer - Professional Kit

Typical values of saturated hydraulic conductivity according to soil type, source: FAO.

Soil type Infiltration rate (mm/hour)

Sandy less than 30

sandy loam 20-30

free 10-20

clay loam 5-10

clayey 1-5

Below are some results from actual tests:

Portable Infiltrometer

In the same way that the initial soil moisture reading has to be taken, it is interesting to take the final readings at the different depths, in order to know how saturation is reached and at what depths. It is also useful to take the VWC readings during the whole process and check how the value becomes constant when saturation is reached, at the same time as the saturated hydraulic conductivity.