| Themes > Science > Earth Sciences > Geology > Soils > Soil Composition > Components and Structure > The Solid Part of Soil |
About 90 percent of the solid part of soil is composed of tiny bits of rocks and minerals from which the soil was foamed. These particles are referred to as sand, silt, or clay, depending on their size. Most soils contain a mixture of these three types of particles. These components of a soil are largely unalterable - there's not much you can do to change them. The remaining 10 percent of the solid part of soil is the organic fraction. This small part of the soil has a tremendous influence on the soils ability to support plant and crop growth. How you manage your soil has a profound influence on the amount and quality of organic matter it contains. The organic fraction of soil is a dynamic substance, constantly undergoing change. This vital bit consists of living organisms, including plant roots and bacteria as well as dead plant residues and other wastes. The total weight of the living organisms in the top 6 inches of an acre of soil can range from 5,000 pounds to as much as 20,000 pounds. The continual decomposition of organic residues results in the formation of humus and the release of plant nutrients. The fertility of your soil - its capacitor to nurture healthy plants and crops - depends on the health, vitality, and diversity of the organisms that live, grow, reproduce, and die in the soil. Through the activities of soil microbes, which can number in the billions in every gram of healthy topsoil, the basic raw materials needed by plant and crops are made available at the right time and in the right form and amount. Soil health and humus are interrelated: Health is the vitality of the soil's living population, and humus is the manifestation of its activities. Humus is produced by bacteria and fungi as they consume organic material in the soil. These elements keep the soil healthy and easy to work, and help the soil to hold water. The billions of organisms that make up the soil community are dependent on you for their health and well-being. If you provide for their basic needs and cultivate properly to avoid disturbing them too much, the soil organisms will thank you with a healthy, productive soil that your plants and crops will thrive |
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