No Till notes: 'Power of Legumes, part 2'

Modern day agricultural producers are constantly striving to lower production costs and improve their stewardship of the land. Many producers have adopted conservation agricultural systems as a means to lower production costs and improve the health of the soils we work with on our farms and ranches.

Leaving previous crop residues attached to the soil surface helps protect these soils. Using no-till crop production methods that provide minimal soil disturbance when planting and harvesting the crops also improves soil health. As these methods are adopted the soil begins to heal itself and soil aggregation, soil structure and water infiltration and storage is improved.

All of these improvements in the physical characteristics and function of the soil begin to provide a healthy environment for soil microbes to begin increasing in population and diversity. To give you an idea of how large these populations are there are more microbes in a teaspoon of healthy soil than there are people on earth.

Dr. Ray Ward estimates that in a typical Nebraska soil there are approximately 3,550 pounds of soil microbes per acre. Think of these microbes as livestock in the soil and you begin to understand how important it is to supply a large amount of residues per acre to feed these microbes.

We know that these microbes mineralize soil organic matter in the soil as they consume plant residues and plant roots from previous crops grown. We also know that for each percent organic matter in the soil there is approximately 1,000 pounds of nitrogen and 100 pounds each of phosphorous, sulfur, and potassium per acre.

I read through an article written by Jim Hoorman and Rafik Islam, Ohio State University Extension educators. In the article they state that typical soils will release 1-3 percent of the nitrogen stored in the organic matter of the soil per year. The higher the biological activity and the higher the organic matter content of the soil, the more nitrogen and other nutrients will be released through mineralization.

A 1 percent organic matter soil with low microbial activity may release only 10 pounds of nitrogen through mineralization, 1 percent of the 1,000 pounds of nitrogen in the organic matter content. A 2 percent organic matter content soil with good biological activity may release up to 60 pounds of nitrogen to the plants we are growing. This would be 3 percent of the 2,000 pounds of nitrogen available.

As you can see, if you are able to improve the health of the soil, increase organic matter content, and increase soil biological activity, there is a potential to lower production costs of commercial fertilizer needed to produce the crops we grow.

The soil we work with is also much healthier in physical and functioning characteristics. These healthier soils will maintain these benefits forever as long as the soil is managed to maintain healthy soil. This is one of the goals of everyone who has adopted conservation agricultural systems.

On our farm we did some testing of soil microbes in different fields this fall to see how our management affected the populations of these microbes. We found some pretty interesting results that I’d like to share with you next week.