Soil texture test

The size of soil particles determines drainage, aeration, susceptibility to erosion, its

capacity to hold water, and the speed at which organic matter breaks down.

Gardeners notice the work it takes to obtain a good tilth on the soil. Plants are

affected chemically when the size of the soil particles affects its capacity to exchange

cations (CEC) and its pH buffering capacity.

Soil structure concerns how soil particles are aggregated together and can be

improved or destroyed by management practices. The texture of a soil is not easily

changed.

• Water drains more freely through sandy soils

• Clay soils hold more water for plants

• Heavy wet soil tends to stay cold for longer

• Well drained soil is well aerated with atmospheric air beneficial to roots

• Clay and silt are more susceptible to erosion by water and wind

• Sandy soil is quicker to break down organic matter due to high oxygen levels

• Cation exchange capacity is higher in clay and organic matter

• Soil with higher clay and organic content is better able to withstand changes in pH

Particle size

• Over 2.00 mm gravel

• 0.05 - 2.00 mm sand

• 0.002 - 0.05 mm silt

• Less than 0.002 mm clay

Apparatus

• A transparent, straight sided jar with lid

• Soil sample

• Water

Method

• Place the soil sample in the jar with twice its quantity of water

• Replace lid and shake well for five minutes

• Set the jar aside to stand

In due course, distinct layers will appear - see picture. These layers are the different sizes of particles, with the largest at the bottom. Measure the thickness of each band to find the proportions of sand, silt and clay.

Results

Plot % results on the triangular chart to determine the soil texture.

Key to soil texture by feel