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Sustainable Agriculture: Programs

Soils 101

Picture of Cecil soil profile Did you ever think about what causes a soil to be the way it is? Here in Georgia we have many different types of soil. These can be very shallow soils over granite bedrock in the northern mountains, to red clayey soils in the Piedmont, to deep sands in the flatwoods near the coast. These differences in soils are the result of five factors that determine the properties of soil: time, parent material, topography, organisms, and climate. These factors all occur simultaneously, and the interaction of these factors results in a specific type of soil.

When we look at soil, we often think of it as a solid. Actually, soils have four major components: minerals, organic matter, water, and air. These components affect how well plants grow, whether or not water will move into soil or run off the soil surface, how well the soil will retain nutrients, and the types of microbes, fungi and other organisms that live in the soil. An ideal soil will have about 50% solid material (mineral and organic matter) and the remainder will be air and water.

Because soil is the foundation of a sustainable agriculture, it helps to understand the three characteristics most important in soil management: the physical, chemical, and biological properties of soil.