Research Improves Understanding of Soil Organic Matter as Carbon Sink

Scientists at Colorado State University have determined that there are two broad categories of soil organic matter that are different in origin and makeup. “Particulate organic matter” is made up of lightweight, partly decomposed plants and fungi residues that are short-lived and not well protected, while “mineral-associated organic matter” is largely made of byproducts of the decomposition of microbes that chemically bind to minerals in the soil. Professor Francesca Cotrufo explains that particulate organic matter is like the “checking account” of soils: it turns over continuously and supports nutrient cycling but requires regular deposits to stay vital. Mineral-associated organic matter, meanwhile, is the “savings account” that gets a smaller fraction of deposits but is inherently more stable. Conventional agriculture, Cotrufo says, has caused us to exhaust our checking account and start living off our savings.