Soil organic carbon changes after 12 years of no-tillage and tillage of Grantsburg soils in southern Illinois

Many factors including management history, soil type, climate, and soil landscape processes affect the dynamics of soil organic carbon (SOC). The primary objective of this research was to determine the effects of no-tillage and tillage systems on the SOC content after 12 years of controlled treatments. A tillage experiment with three treatments (no-till (NT), chisel plow (CP) and moldboard plow (MP)) was initiated in the spring of 1989 in southern Illinois. The plot area was previously in a tall fescue hayland for 15 years and had a 6% slope. Maize (Zea mays L.) and soybean (Glycine max L. Merr.) were grown in the plot area on a yearly rotation system starting with maize. Periodically, the SOC content of various soil layers, to a depth of either 30 or 75 cm, was measured and expressed on both a gravimetric and volumetric basis. After 12 years, the 0-15 cm surface soil layer of MP was significantly lower in SOC than the NT and CP plots. For all but 2 values, the significance of findings did not change with the form of expression (gravimetric versus volumetric). The surface layer (0-15 cm), subsoil (15-75 cm), and rooting zone (0-75 cm) of all treatments had reduction in SOC on a volumetric basis when compared to the pre-treatment values for sod. At the end of the 12-year study, the MP system had significantly less SOC in the surface layer, subsurface layer and rooting zone than the NT system at comparable depths. After 12 years of tillage under a maize-soybean rotation, the NT treatment sequestered or maintained more SOC stock (47.0 Mt ha−1) than the CP (43.7 Mt ha−1) and MP (37.7 Mt ha−1) treatments. The annual rate of SOC stock build up in the root zone (0-75 cm), above the MP system base, was 0.71 Mt ha−1 year−1 for the NT system and 0.46 Mt ha−1 year−1 for the CP system. For land coming out of the Conservation Reserve Program and returning to row crop production, NT and CP systems would maintain more SOC stock than MP system and reduce CO2 emissions to the atmosphere.