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Soil is produced from many different combinations of factors and conditions: if you have a knowledge of the various soils it will help you to grow better plants.
Many garden soils are man made, some were formed by breaking down (disintegration, decomposition, weathering, etc.) of rocks, minerals and plant and animal remains on the surface of the earth. Soil could be considered as a living substance, that is for sure.
If we want to get technical, then we would know that the finely-divided mineral portion is commonly called the inorganic portion, this gives soils their body, mass, bulk and rigidity, usually 90 to 98 percent of the solid portion.
The decaying plant and animal materials make up the remainder of the mass. Now there are spaces in between and these are called pore spaces. Each of these spaces can be filled with one of the following air, water, soil solution, smaller soil particles, roots microscopic plants and animals or all kinds of combinations of these substances.
It is the arrangement of the soil particles that determines the amount of pore space or porosity, this ranges from 40 to 70 per cent by volume in the various soils.
Now I will attempt to list and describe various garden soils for you.
Sandy Soil: A sand or sandy soil has large particles sizes and large spaces between these particles, therefore although each space is larger, the total voluma of pore space in sand is smaller than in a fine-textured soil. These large pore spaces serve as good channels or passageways for water and air to enter and move down in the soil. Since the water moves rapidly through this soil, it is not retained long enough for plant use so sandy soils are liable to be droughty or in need or watering often. They also tend to warm up earlier in the spring and because of the good drainage, low moisture content, and small amounts of fine,sticky materials (colloids) this makes it possible to work sandy soils almost anytime.
Clay Soil: This soil has very small pore spaces, much smaller than in a sandry soil, and this makes the spaces so small that water movement thru them i retarded most of the time, and for that reason the clay soil absorbs water very slowly. You will need to water this soil very gently or most of the water will just run off the soil. Now once the water penetrates it is held more tightly than in sandy soils and is held for a long period of time. Never work this soil when it is very wet or extremely dry, this will compress the clay particles together and it becomes brick-hard. This will destroy the granular structure.
Silt Soil: This is the best soil for a garden as it has many advantages of the above two extremes and a few disadvantages as well. Silt soils are not the ideal texture for a general garden soil, but are by far better than either the sandy or clay soils.
To improve a sandy soil for gardens you will need to add a fine material such as clay, or fine organic material like humus or peat, althought it is very difficult to break down the clay into individual particles so it can be mixed with sand.
Organic matter is more satisfactory. Wood ashes are used sometimes, lime can improve the physical conditions of a sandy soil also, the best form of organic matter would be peat, leaf mold, manure or compost, but not too coarse these additions.
To improve a clay soil you would add coarser materials so that you can coagulate the fine particles into larger ones. Sands can be used to improve clay soils, but coal ashes can also be used. Organic matter is one of the most desirable materials to improve the physical condition of a clay soil. I like to use granular organic materials such as peats, leaf mold, rotted manure, compost or you could use sewage sludge. Your purpose is to hold the fine particles apart for better, air, water and root penetration.
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