Soil is meant to be covered. This motto has been a National Resources Conservation Service staple for years and is the second component of soil health principles. For the longest time this statement was spoken by the NRCS as a reminder to farmers that no-till planting led to reduced soil erosion.

Now as we learn no-till is not enough to build and maintain good soil health, we want soil covered throughout the year with something living; crops in the summer and cover crops through the late fall and winter.

Cover crops not only jump-start and increase biological activity in the soil, their fibrous roots really improve soil structure which can remove surface compaction and allow increased air and water infiltration.

These improvements in turn increase the biological activity jump-starting the cycle again. By regularly following row crops with a cover you not only control fall and spring weed pressure, you provide growing plants which can scavenge nitrogen and hold winter precipitation that may otherwise not be utilized by next year’s crop; most importantly you build organic matter.

Research has shown 1 percent of organic matter contains 10,000 pounds of carbon, 1,000 pounds of nitrogen and 100 pounds of phosphorus and sulfur.

Recalling what we know about the soil food web and the nitrogen cycle we understand organic nitrogen generated by the feeding and decomposing of several levels of microorganisms is mineralized into inorganic nitrogen which can be utilized by crops.

Mineralization rates are typically at a rate of 2 to 3 percent which means 1 percent of organic matter provides 20 to 30 pounds of available nitrogen. So having an organic matter level of 3 to 5 percent can mean nearly all of a corn crop’s nitrogen needs can be supplied solely by the soil.

How long does it take to build organic matter to these levels? It depends; it typically takes 5 to 7 years to take to rebuild soil from tillage operations however once converted to a no-till system the addition of cover crops can quickly increase organic matter, however only planting rye or wheat after corn and soybeans is typically not enough to significantly increase organic matter. To really improve soil structure down a foot or more in depth cover crops need to crop all season so their fibrous roots can reach maturity and allow a significant amount of leaf litter to provide year round food sources for microorganisms.

In future articles we’ll learn more about the microorganism that feed on plant residues and later we’ll learn about the benefits of diversifying cover crops and how this diversification exponentially improves soil health.

Andy Gaver is a conservationist with the USDA Natural Resources Conservation Service in Butler County.