Protecting Soil Carbon

By Woody Woodruff

When I first started giving presentations to farmers on why soil health is important to farming, my research on the matter brought me to a published document from University of Illinois. “Study Reveals that Nitrogen Fertilizers Deplete Soil Organic Carbon”, Published October 29, 2007. Using results from over a hundred years of continuous field trials at the Morrow Plots as well as from other published research from around the world, University of Illinois soil scientists Saeed Khan, Richard Mulvaney, Tim Ellsworth, and Charlie Boast found that excessive application of synthetic nitrogen stimulates soil microbes which feed on organic matter. Over time, this enhanced microbial activity consumes carbon in the soil from crop residues, and the net result being a reduction in soil carbon. Manure was not having the same level of effect on depleting soil carbon as synthetic fertilizer was having. Mulvaney and his colleague conclude: “In the modern era of intensified agriculture, soils are generally managed as a commodity to maximize short-term economic gain. Unfortunately, this concept entirely ignores the consequences for a vast array of biotic and abiotic soil processes that affect air and water quality and most important, the soil itself.”

Another University of Illinois researcher, Dr. Ken Olson, looked at soil carbon losses as they relate to basic changes in the different tillage practices — like moldboard plowing verses no-till planting. Olson’s research was attempting to understand the degree to which soil organic carbon loss can accurately be measured by just referencing the type of tillage practices. It is understood that deeper more aggressive tillage has the ability to release more stored soil carbon than no-till can, but to quantify by just tillage type is trickier to prove with certainty given a whole host of variables that must be accounted for:  machinery types, residue levels, different slopes, soil types, etc. Olson eventually concluded that aeration, drainage, tillage, more intensive crop rotations, use of synthetic fertilizers, erosion and lack of cover crops can all play a key role in depleting soil organic carbon stocks.

Why is carbon so important to soil though? Carbon is at the root of ecosystem services. More soil carbon means more nutrients naturally being available in the soil for plants. Soil carbon adds to the soils’ water holding capacity, which in turn keeps more water in the soil for plants to drink and less soil erosion running off the field. Holding on to soil carbon deep in the soil keeps toxic levels of carbon dioxide from being released into the atmosphere, causing climate issues. But soil carbon is much more than just an environmental service.  Carbon is the basic building block of life. All living organisms contain carbon.  Virtually every molecule in the body, except water contains carbon. Sugars, DNA, proteins, and fats contain carbon. Carbohydrates without carbon would just be water. We cannot live without carbon. In fact, our own bodies process carbons in much the same way soil does. For example, think of tillage of the soil in the same way you think of white flour and whole grain flour. Heavy tillage is just like processed white flour and no-till is like whole grain flour. We all know that whole grain flour is better for us, but why? The extensive grinding and processing of wheat into white flour makes it easier for our bodies to convert those carbohydrates into sugars, which causes a harmful effect on our body’s rate of metabolism. Excessive tillage does the same thing to the organic matter in the soil, speeding up the rate at which microbes eat the carbon. Eating whole grains and practicing no-till helps these two types of living bodies (soil and human bodies) process carbon at a safer, less toxic rate.

Given the importance of carbon to the well-being of life on earth, a correlation between carbon loss in our soils due to the rise of industrial agriculture in the last century, and an increasing rate of poor health in humans seems only logical.