Types of soil
Soil types are important. Types of soil are determined largely by texture, a word often used in the wrong sense. It means simply particle size, such as fine sand, gravel, silt, clay, and so on.
Particle sizes in soils range something like this:
Clay – 002mm or smaller
Silt – 002 mm to .05 mm
Fine Sand – 05 mm to .25 mm
Sand – 25 mm to 1.0 mm
Gravel – 1.0 mm to 32 mm
Stones – over 32 mm
Organic matter in soils may range in size from as large as entire plants that have been dug under, to as small as humus particles so fine that they form colloidal solutions. (In a colloidal solution the minute particles do not settle out, but float indefinitely.)
Based on the preceding information, according to particle size here is a soil classification.
Types of soil are to do with the mechanical makeup of the soil. The type of soil does not give much clue to the value of a given soil for growing plants. By habit we associate loams with rich soils, yet certain loams may be poorer than some clay or sandy soils.
The types of garden soil concern you in three vital ways.
First, many recommendations for applying fertilizer, for treatments to adjust pH (acidity-alkalinity), and for other applications of chemical substances to soil give different rates for clay, sand, and other types.
Second, knowledge of garden soil types gives some clue as to how well a soil will hold fertility. (Fall feeding is possible for a lawn on clay loam soil, for example, where this would be unsuccessful on a light sandy loam.)
Third, knowing your types of soil will often tell you in advance whether it will drain well or will puddle and wash under heavy rains.
These three points are chiefly important now, at the beginning of our discussion on converting a native soil into Gardener’s Loam. They will lose their importance once we have incorporated soil amendments and extra organic matter into the soil, for then the original soil type will be so modified that it will have to be evaluated in light of its new characteristics.
An accurate test of texture and type requires an involved laboratory procedure. A rough check for soil types, accurate enough for gardening purposes, can be made by the soil wash test.