Garden Soil Preparation - Types of Soil

Soils are made up of four major components - inorganic particles, organic matter, water and air. Ideally, a good soil should be composed of about 50 percent inorganic and organic particles, 25 percent water and 25 percent air.

Basically there are three major types of soil - sandy, clay or loam.

Sandy Soil

Are composed of large particles or aggregates, making them extremely porous. They generally are poor because when water is added to them they drain rapidly, leaching soluable nutrients. Sandy soils have to be watered more frequently. The additions or organic matter greatly improve sandy soils by adding fertility and aiding them in retaining moisture.

Clay Soil

Are composed of minute particles, microscopic in size. They are most difficult to manage since they are heavy and often sticky when wet. Clay soils are slow to absorb water when dry, but once they become wet they retain moisture readily and do not dry out as rapidly as sandy soils. Clay soils should not be worked when they are wet since they tend to compact, making them impervious to air.

Clay soils may form hard to manage clods when they dry and frequently form a crust on the soil surface making it difficult for germinating seeds to penetrate through the layer.

Avoid walking, spading, plowing or running equipment over wet clay to minimize compaction. Organic matter improves clay soil by breaking up the clay particles and making them more porous. Sand is often added to clay in small plots or beds to make them more porous.

Loam Soil

Ideally, the best soil is a loam soil which has a combination of sand particles, clay particles, silt particles and organic matter. Unfortunately, most gardeners are not blessed with this ideal type of soil.

Gardeners must also understand the term pH and its relationship to successful plant growth. Although the term pH is frequently used, it has been surrounded by a certain aura of mystery. The term is simply a measurement of soil reaction or the acidity or alkalinity of the soil. At certain levels on the pH measurement scale, essential plant nutrients turn into insoluable forms that cannot be assimilated by plants.

The measurement scale for pH is much like a thermometer. The scale ranges from 0, which is strongly acid, to 14, or strongly alkaline with 7.0 on the scale being neutral. Some plants live in extremely acid soil which others can tolerate an alkaline soil. However, most plants produce at their optimum from about 5.4 to 6.9 on the scale.

The importance of knowledge of pH to nutrient availability can be demonstrated by the availability of phosphorus. When the pH is high (alkaline) above 7.5 phosphorous becomes tied up in an insoluable form, unavailable to plants. When the pH drops below 7.3 it is again released in soluable form. But when it drops as low as 5.0 the phosphorus again becomes tied up in the soil. It is difficult to change the pH of the soil. However, by addition of organic matter and soil sulphur the tendency is to form a more acid reaction.

Soils on the alkaline side are watered deeply to leach soluable salts, which are alkaline. In the Eastern United States soils are more acid and lime is added to increase the pH. One of the best methods of gaining an understanding of your soil is through soil testing. The soil test gives specific information as to soil type and texture, the percent organic matter, percent soluable salts, percent and soil pH. In addition, specific fertilization and cultivating information will be made based on your individual soil sample.

http://en.wikipedia.org/wiki/Soil_type