Growing Food: A Guide to Food Production

Figure 6. The Soil Triangle

Describing Soil Types / Soil Textures
It is not normally necessary to go to the trouble and expense of a mechanical soil
analysis. Usually it is quite adequate to be able to describe a soil by taking some of the
moist soil in your hand and feeling it between your thumb and the palm of your hand:

Sensation Description Particle Size

(mm)

Small stones or gravel

Gritty feeling

Also a gritty feeling between the teeth

Gritty feeling, and also makes your hands

dirty

Smooth, silky feeling but the soil cannot

be polished when damp between your

fingers

Smooth, silky feeling and you can polish it

between your fingers

Gravel

Coarse sand

Fine sand

Loam

Silt

Clay

2.0+

0.2–2.0

0.02–0.20

0.002–0.020

0.002–0.020

<0.002

The colour of soil can also provide some information; dark brown or nearly black soils
are normally rich in humus, while light brown or red soils often contain mineral oxides
such as iron. More formal classification can be made using a Munsell Colour Chart.
The soil structure can be described by looking at the size of the soil particles:
Loose—when the particles are mostly separate, such as in sandy soils;
Crumb
of soil, typical of loam soils;
Solid—when there are large blocks of soil.

Clay 100% Sa

Sand 100% Silt 100%

50%

30%

20% 80%

70%

C 50%

Cs Cz

Lcs Lb Lcz

Lz Z

Lm

Sa La

La

Lm

Lb

Lcs

Lz

Lcz

Z

Cs

Cz

C Clay

Silt clay

Sandy clay

Silt

Silty clay loam

Silt loam

Sandy clay loam

Heavy loam

Medium loam

Light loam

Sand

19

Friable (“ ”)—when there is a mixture of separate particles and smaller lumps

GROWING FOOD – THE FOOD PRODUCTION HANDBOOK