Role of Organic Matter in Soil


Experienced gardeners will tell you that not all soil is created equal. All the best plants and hard work in the world won't add up to much without a growing medium that provides what your plants need. One effective way to improve the quality of your soil is to amend it with organic matter.

Organic Matter Defined

Organic matter is plant or animal material that's decomposing. Don't confuse it with organic material, which are leaves, manure and other natural substances that have yet to decompose. Once these materials are broken down by microorganisms to a stable state, they become organic matter, or humus. Sometimes, organic matter is derived by composting yard clippings and food waste or by composting manure.

Improving Moisture Retention

Soil is made up of water, air, minerals and organic components. Soil quality is affected by its ability to retain water. Organic matter can significantly improve that ability. Most organic matter is spongelike, holding up to 90 percent of its weight in water. What's more, most of this water is released to plants. By contrast, clay soils hold a great deal of water, but don't readily release it to plants. A garden that has been properly amended often requires much less irrigation than one with poorer soil.

Nutrient Enrichment

Organic matter is nutrient-dense and releases this nutrient content into the soil. This, of course, boosts the potential of plants. Organic matter also increases the number and activity of microorganisms in the soil. Over time, this helps produce more of the nutrients required by plants. The release of nutrients from organic matter occurs primarily in the spring and summer, benefiting summer crops

Improving Soil Structure

Ideal soil has a granular, crumbly texture that allows water to drain through, and oxygen and carbon dioxide to move freely through spaces. The presence of humus in the soil binds mineral particles in clusters, ultimately contributing to the preferred texture. Improved soil structure, along with increased water retention, creates resistance to erosion.

Improved Disease and Pest Resistance

The presence of sufficient organic matter in soils is beneficial in other ways, as well. For instance, plant deficiency diseases tend to be less severe in soils with good levels of organic matter. Additionally, some of the beneficial microorganisms found in rich soil keep harmful nematodes in check.

Keywords: organic matter, soil improvement, humus in soil

About this Author

Dana Hall McCain is a freelance writer based in Dothan, Ala., and is a a regular contributor to numerous regional publications. She writes features and columns on a variety of topics, including the outdoors, faith and health/wellness. She received a Bachelor of Arts from Auburn University in public relations/communication in 1995.