What Does Amending Your Soil Mean?

Amend, Fertilize and Mulch

• Soil amendment is different from fertilizing or mulching. Amendment is concerned primarily with improving soil's structure, drainage and acidity. Amendments are tilled deeply into the soil to thoroughly combine them with the dirt. Fertilizer, on the other hand, is intended to address nutrient deficiencies in the soil. Fertilizer is usually spread on top of soil or applied in a liquid form. Mulch is laid on top of soil to reduce evaporation, inhibit weed growth, and moderate soil temperature.

Organic Amendments

• Organic soil amendments come from living sources and include compost, wood ash, peat moss and grass clippings. When these items are tilled into the soil, they slowly decompose, increasing the porosity of the soil and allowing for better aeration and water flow, as well as increasing the soil's ability to hold appropriate amounts of water and nutrients. Organic amendments also provide nutrients for both plants and for beneficial bacteria and soil-improving organisms like earthworms.

Inorganic Amendments

• Inorganic amendments come from non-living sources or are man-made. They include sand, gypsum and vermiculite. Inorganic materials do not decompose and are generally used to improve soil's structure by making it more porous. Sand mixed with compost, for example, is often recommended for heavy clay soils, as it helps to break up the clay to provide better drainage. Colorado State University Extension does not recommend adding sand alone to clay soil, stating that it creates a soil texture that resembles concrete. Lime and sulfur are inorganic soil amendments used to raise or lower soil pH.

Choosing Amendments

• To determine what amendments your soil requires, examine and test your soil. Look at the soil to see what type it is and whether it is well-drained. If it is too dry or sandy, add amendments that help retain water and nutrients. If it is wet or contains a lot of clay, add materials to improve drainage and air flow. A soil test kit measures your soil's pH; add acid or alkaline ingredients to achieve the optimum 6.5 pH. A soil test kit can also determine how fertile your soil is and what nutrients it may be lacking.