Characteristics That Determine the Usefulness of the Soil

Soil Texture

• Soil texture is one of the most talked about and important characteristics that soil presents. If you've ever heard the terms sandy, loam or clay used to describe soil, it is the texture to which these terms refer. The size and type of mineral and organic particles that compose a soil determine its texture. The three basic particles are sand, silt and clay. To determine texture, researchers separate and weigh the different particles and determine the percentage in which they are present in the soil. They can then determine the overall texture, such as sandy loam or loamy clay.

Soil Permeability

• The soil's texture helps to determine its permeability and infiltration, which have to do with the way water moves through the soil. Soils with a coarse texture, such as very sandy soils, have high infiltration and permeability rates; water drains readily through them. Finer textures, such as clays, prevent the flow of water, and can cause serious problems for some plants. For plants with deep roots, a nonpermeable soil will result in the plant not getting enough water due to restricted flow. This availability of water determines which types of plants can be grown in a particular soil.

Soil pH

• Just as with liquids, soils also have a measurement of pH, or acidity level. On the pH scale, a reading of 7 is completely neutral. A number lower than 7 indicates high acidity; a number higher than 7 indicates alkalinity. The acidity level of the soil determines which nutrients the plants can absorb. For example, neutral-pH soils tend to be high in phosphorus, while acidic soils are high in aluminum and iron. Soils with a pH reading between 6 and 7 can generally grow any type of plant; some plants can tolerate higher or lower acidity levels, based on their nutrient needs.

Determining Soil Characteristics

• In general, you need to run a soil test to determine the characteristics of your soil. This test involves removing samples from multiple areas of your garden or lawn and sending the samples to a university of extension service laboratory. There, researchers can determine these characteristics and provide advice regarding the types of plants you can grow. These researchers can also recommend soil amendments to change the pH, texture and permeability of your soil if necessary.