Soil Organic Carbon Changes Impacted by Crop Rotational Diversity under No-Till Farming in South Dakota, USA

Diverse cropping systems and no-till (NT) are often suggested as management tools to improve soil organic carbon (SOC) and soil properties in fields with a history of intensive tillage. The present study was conducted to evaluate the interaction of tillage and rotation systems on SOC and selected soil properties. The long-term site initiated at Beresford, South Dakota in 1991 is comprised of two tillage [NT and conventional-till (CT)], and three crop rotations [maize (Zea mays L.)-soybean (Glycine max L.) (MS); maize-soy-bean-wheat (Triticum aestivum L.) (MSW); and maize-soybean-wheat-oat (Avena sativa L.) (MSWO)]. Soil sampling was conducted in the maize and soybean phases of each rotation in 2014. Soil samples were collected from four depths (0- to 7.5-, 7.5- to 15-, 15-to 30-, and 30- to 60-cm) after crop harvest, and analyzed for SOC, total nitrogen (TN), bulk density, water aggregate stability (1-2 mm), and light fractions of carbon and nitrogen. Data showed that after 23 years, the 4-yr rotation significantly increased SOC concentrations up to 30-cm in both tillage systems compared to that under 3-and 2-yr rotations, which subsequently decreased bulk density in the 4-yr rotation for these depths. There was also a significant interaction between tillage and rotation. The NT system significantly increased SOC relative to CT within the 4-yr rotation in the top 30 cm. Data from this study revealed that long-term use of diverse crop rotations (MSWO) under NT system in South Dakota, USA, improved SOC concentrations and other soil properties compared to that of less complex (MS) systems.