Last week featured an extremely condensed version on the formation of soils. Now let’s briefly examine the roles of soil in our world. First, broad definitions of the soil are helpful. Soil can be defined as the skin of the earth or the area of exchange between the earth and the atmosphere. The soil is also defined as a dynamic, living organism consisting of organic and inorganic components. While soil profiles (the vertical extent of the soil) vary in depth from inches to over ten feet, let’s assume a depth of 3 feet. The distance from the earth’s surface to the center of the earth is a little less than 4,000 miles. So out of that distance, 3 feet or 0.00001% of that distance is what we use to support terrestrial life as we know it. Now that we have some perspective, what functions does the soil serve?
· Studying the soil can provide a record of what has happened in the recent and more distant past biologically and climatologically
· Soils are a media for plant growth. While we can grow plants and animals without soil, soil provides the most efficient, cost effective media. The soil serves as physical support for plants by anchoring roots.
· Soil provides oxygen to plant roots and organisms living in the soil while removing carbon dioxide using pore space.
· Soils both store water and release it to plants and other organisms.
· Soils moderate temperatures both in the soil environment and near the soil surface, helping protect living organisms from temperature extremes.
· Soils help filter out toxins and prevent them from poisoning living organisms and keep them out of groundwater.
· They store and provide essential elements necessary not only for plant life but all life. Originally many of these elements derived from the parent materials as they broke down. Later soils cycle nutrients through the decomposition of organic matter and store fertilizers.
· Soils regulate and purify water supplies. Wetland soils also help in preventing or minimizing flooding.
· Soils serve as a source and sink for various compounds including toxins, nutrients, and carbon dioxide. The microorganisms in soil breakdown and recycle waste and dead organisms releasing nutrients and breaking down organic matter. If this didn’t happen, we would be buried under a mile or two of undecomposed organic materials and waste.
· Soils modify our atmosphere. Ask anyone who lived through the Dust Bowl. They also influence the atmosphere through affecting the amount of water vapor in the air; and act as a sink/source for CO2 and O2.
· Soil serves as a habitat for numerous micro- and macro- organisms.
· Soils are an engineering medium in the following ways: building materials (sands, clays), an actual place to live, media for roads, and support for various structures.
The list could be longer but this gives you an idea of all that soils provide. While the exact definition of soil is “the relative proportions of sand, silt, and clay,” a better way to look at it is as a 3-D natural body composed of soil, roots, animals, rocks, artifacts and other items. Next week will start to put together how a soil forms with the information from this week into what it means for us, not only for agriculture but for all of society.