Are There Different Types of Dirt?

Taxonomy

• Soil scientists classify soils according to certain physical and chemical properties that depend on a soil's parent rock materials, age, geographic location, climate and biological factors. Named soils are called "soil series." These soil series are at the bottom of the classification hierarchy. The top of the hierarchy is made up of 12 soil orders from which 64 suborders descend. Suborders are above 300 great groups, which are above 2,400 subgroups. These subgroups, in turn, are above the 20,000 types of identified soils.

Garden Soils

• The very uppermost soil level is the level with which most people come into contact. Garden soils are composed of clay soils, loam soils or sandy soils but are most likely a combination of these three types. You will see articles and statements speaking about sandy loam or clay loam, for instance. The authors are speaking about the soil's texture and porosity. Clay soils tend to be heavy, dense soils prone to quick surface drying and deep saturation. Clay soils lack aeration and microbial activity, which prevents good root development. Sandy soils are highly porous. Water drains from sandy soils quickly and with it valuable nutrients are washed away. Loam soil is considered the best garden soil because it contains the optimum amount of sand for drainage, loam for nutrients and clay for water retention.

Soil Amendments and Tests

• Improve your soil's quality by amending it with supplements. Clay soils benefit from compost. The addition of organic matter lightens the soil. As compost decomposes, microbes are introduced that help aerate and turn compacted soil. Sandy soils also benefit from additional organic material. Increasing sandy soil's bulk allows moisture and nutrient retention. Apply mulch to sandy soil's surface and moisture retention improves. Clay soils tend to have high acid levels that may cause plant problems. Sandy soils frequently exhibit alkaline conditions. Each of these situations causes nutrient disruptions that can potentially require fertilization and nutritive supplements. Take soil samples from various sections of your yard and garden. Take your sample to a university extension for soil analysis to receive customized fertilizer recommendations.

Considerations

• You can improve improve aspects of your garden soil but cannot change the overall structure. Sandy soils, even when improved with the addition of black dirt or compost, will eventually revert back. Over time, soil's original structure dominates, which is why gardeners with sandy soil must continually amend their soil and why soil tests should be conducted every two to three years.