Spring is finally upon us! That means we should soon be working with soils in our fields, gardens and landscapes.
The foundation to a successful crop production system depends on good soil. Good sound soil management is required to meet essential plant needs for water, nutrients, oxygen, and a medium to hold their roots with as little management as possible.
If we start to understand soil and its properties, hopefully we can become better managers of our soils.
Soil by dictionary definition: 1.) a natural medium for plant growth, whether or not it has discernible soil horizons, 2.) unconsolidated mineral or material on the surface of the earth resulting from and influenced by time, parent material, climate, organisms, and topography.
Components of soil are made up of different sized mineral particles, organic matter, air and water.
The relative amounts of mineral and organic matter determine the physical properties of soil. There are three main properties of soil: Soil Texture, Soil Structure, and Soil Porosity.
Soil Texture is determined by the relative amounts of three groups of soil particles. These would include sand, silt and clay.
You can determine your soil’s texture by how it feels. Does it feel gritty, greasy, or floury? Sandy soils would feel gritty. Silty soils would feel flourier when they are dry and more greasy when wet. Clay would be greasy feeling all the time.
Soil Structure refers to the way soil aggregates, particles, and pore space are arranged with respect to each other. Unlike texture which is inherent and difficult to change, through management of our soils we can influence the structure. Such things as plowing, cultivating, applying lime, adding organic material, and stimulating biological activity in our soils can change soil structure.
The shape and arrangement of soil particles help determine soil porosity.
Organic matter is a very important part of our soils. Organic matter serves as a reservoir of nutrients and water in the soil, aids in reducing compaction and surface crusting, and increases water infiltration into the soil.
Many times we think of organic matter as the plant and animal residues we incorporate into the soil. This is actually organic material, not organic matter.
What’s the difference between organic material and organic matter? Organic material is anything that was alive and is now in or on the soil. For it to become organic matter, it must be decomposed into humus.
Humus is organic material that has been converted by microorganisms to a resistant state of decomposition. Organic material is unstable in the soil, changing form and mass readily as it decomposes. As much as 90 percent of it disappears quickly because of decomposition.
Organic matter is stable in the soil. It has been decomposed until it is resistant to further decomposition. Usually, only about 5 percent of it mineralizes yearly.
That rate increases if temperature, oxygen, and moisture conditions become favorable for decomposition, which often occurs with excessive tillage. It is the stable organic matter that is analyzed in the soil test.
Only a small portion of soil volume is made up of organic matter (Agricultural soils average only 1-6 percent). An acre of soil measured to a depth of 6 inches weighs approximately 2,000,000 pounds, which means that 1 percent organic matter in the soil would weigh about 20,000 pounds per acre.
It takes at least 10 pounds of organic material to decompose to 1 pound of organic matter, so it takes at least 200,000 pounds of organic material applied or returned to the soil to add 1 percent stable organic matter under favorable conditions.
The benefits of organic matter include:
• Organic matter is a reservoir of nutrients that can be released to the soil. Research has shown each percent of organic matter in the soil releases 20 to 30 pounds of nitrogen, 4.5 to 6.6 pounds of P2O5, and 2 to 3 pounds of sulfur per year.
• It affects water-holding capacity of soil and is somewhat like a sponge, with the ability to absorb and hold up to 90 percent of its weight in water. A great advantage of the water-holding capacity of organic matter is that the matter will release most of the water that it absorbs to plants.
• Organic matter causes soil to clump and form soil aggregates, which improves soil structure.
• Research suggests that increasing soil organic matter from 1 to 3 percent can reduce erosion 20 to 33 percent because of increased water infiltration and stable soil aggregate formation caused by organic matter.
This is only the beginning to understanding your soils. Begin now looking and working with your soils – good sound soil management can begin and the dividends of better crop production can hopefully be seen. Further needs would be to conduct a soil test.
Knowing your soil fertility will certainly help in knowing at what rates and what nutrients your crops/plants will need.
Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for 29 years, currently serving Clinton County and the Miami Valley EERA.