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An ideal soil contains 25 percent air, 25 percent water, 45 percent mineral material and 5 percent organic matter. Each component contributes essential environmental characteristics toward the growth of the plants. If a soil lacks any of these components, plant growth is limited.
Air is essential because all plant cells must carry on a vital life process called respiration. This process burns or oxidizes the sugars and releases energy. Any cells that are not respiring quickly die. The roots of all plants are composed of living cells and for that reason each cell must have oxygen available as needed. This comes through the pore spaces in the soil. When soil is badly compacted the air cannot permeate and the roots will not grow. This results in poor growth and eventually leads to death of the plants.
The water in the soil is not the water that is available to plants for growing. Soil water is tightly bound and can only be measured when the soil is air-dried. Water that is available to plants can be added as irrigation water. This must drain through the soil freely because the drainage moves oxygen into the soil.
The mineral content contains three kinds of soil particles. They are sand, silt and clay. The relative proportions of these components determine the soil texture. Soil with near-equal amounts of three components is a loam. Sandy loam is usually considered an ideal soil. Soils with a high percentage of any of the particle sizes are unsatisfactory for growing plants.
The final component of the soil is organic matter. Typically Utah soils are very low in organic matter, with less than 1 percent instead of the 5 percent that an ideal soil contains. This makes the soils low in available nutrients and prevents them from being easily worked.
Organic matter is the most easily manipulated of all the soil particles. It holds water well and can retain nutrients. It cures a variety of ills in problem soils. In clay soils the waxes and lignins in the organic matter glue the tiny clay particles into small aggregates. This allows the water to drain through and allows air into the soil. In sandy soil the organic portion holds the water and the nutrients. In both types the organic matter improves the soil and allows better plant growth.
All kinds of organic matter are used to improve garden soils. These include commercial products, animal manures, homemade composts and many others. Adding large amounts each year creates a productive, workable soil in your garden.
