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Soils are classified according to their clay, silt and sand content. The size and proportion of these mineral particles affects the chemical and physical behavior of the soil. The main categories of the soil are: loam, clay, sandy, silt, organic or peat, chalk or limestone soils. Most garden soils are combinations of several of these types and it can vary in different parts of the garden, so is possible that your garden will have different type of soil in different places.

Soil Types by Structure

Loam soils have the ideal balance of mineral particle sizes, with an amount of 8 to 25 per cent clay. This means that it provide good drainage and water retention to the plants and it also is highly fertile. This is the type of soil that any gardener wants to have in its garden as this is what we call good garden soil. It can be helped to maintain its fertility by adding organic matter.

Clay soils have more than 25 per cent clay particles. They are wet and sticky, often highly fertile but heavy, with slow water drainage. They are easily compacted, warm up slow in spring and may bake hard in summer. This type of soil can be easily improved with the addition of well-rotted organic matter, gritty sand or fine bark chippings. This will help to improve the soil drainage, aerate the soil and makes it easier to work.

Sandy and silt soils have low proportion of clay particles, usually under 8 per cent, so they are much less water-retentive than clay. Sandy soils are dry, light and free-draining, easy to work but relatively infertile so they need frequent irrigation and feeding. They warm up quickly in spring and can be easily improved with a good addition of organic matter. Silt soils are more retentive and fertile than sandy soils but tend to compact more easily.

Organic or peat soils are wet – as they are moisture-retentive, dark and acidic but they support excellent plant growth if they are drained, fertilized and limed.

Chalk or limestone soils are pale, shallow, stony, free-draining and alkaline, with moderate fertility, allowing organic matter to decompose rapidly.

It is important to know what type of soil you have in your garden. You can identify your soil by rubbing a small amount of moist soil between your fingers. If the soil is sandy it will feel quite gritty and will not stick together or form a ball because the sandy particles will not stick together. A sandy loam is more cohesive. A silt soil feels silky or soapy to the touch. A silty loam may show imprints when pressed with a finger. A loamy clay soil will hold together well and may be rolled into a cylindrical shape. Heavy clay soil may be rolled even more thinly and develops a shiny streak when smoothed. All clay soils feel sticky and slightly heavy.

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