Soil Carbon Sequestration and Redefining Soil Health.

The role of soil carbon in positively affecting crop and fiber yields and ecosystems services and in influencing atmospheric composition has received much attention. Reducing soil disturbance through reduction or elimination of tillage has been promoted as a best management practice to sequester soil carbon. However, the role of reduced tillage or no-till in sequestering soil carbon does not have a scientific consensus. Less soil disturbance has been shown to increase surface carbon concentrations significantly compared to disturbed or tilled systems. In comparing disturbed and less disturbed soils to deeper depths, particularly beyond the plow layer, studies show little difference in soil profile carbon amounts. Does stratifying carbon in the soil surface of reduced till or no-till soils have advantages over diluting it in the soil profile of tilled soils? Increasing soil structure, water infiltration and nutrients in the surface of less disturbed soils has a positive influence on soil health and productivity. On the contrary, increases in greenhouse gases, particularly nitrous oxide, can occur due to soil compaction, increased microbial activity that decreases oxygen levels, increased available nitrogen from mineralization activities and concentrating nitrogen applications during application. Increasing carbon inputs in the form of plant residues, organic amendments such as composts, food waste and manures, and cover crops will be required to increase soil carbon regardless of the level of tillage disturbance. This intensification, particularly the use of organic amendments, has the most benefit if tilled into the soil. If left on the surface, nutrient losses from volatilization and runoff can ensue. The intensification of future cropping systems will require an increase in soil carbon to fully benefit from the positive effects of improving soil productivity and health. The question becomes, “What is the level of tolerable soil disturbance?” to produce healthy soils.