Impacts of Bio-Char and Cover Crops on Soil Carbon Sequestration and Related Soil Properties.

Enhancing or improving soil properties such as soil organic carbon (SOC) pools is essential to maintain or sustain soil productivity and environmental quality. Many studies have compared soil properties under contrasting tillage and cropping systems, but few have assessed how addition of biochar and cover crops to cropping systems management practices may influence soil properties and sequester atmospheric C. Thus, the objective of this study was to evaluate short-term changes in wet soil aggregate stability and concentrations of SOC and total N for an ongoing experiment established on a Sharpsburg silty clay loam in eastern Nebraska in spring 2014. The treatments in triplicate were: addition of 1 Mg ha^-1 of wood biochar, wood biochar plus inorganic N fertilizer, Oat + winter wheat + cereal rye cover crops, and control. Biochar and N fertilizer were injected to a soil depth of 7.5 cm. The experiment is under NT with corn-soybean rotation. Soil samples were collected at 0-5, 5-10, and 10-20 cm depths in summer 2015. Results showed no differences in SOC, total N, and water stable aggregates among the treatments. Mean SOC pools were 23.9 Mg ha^-1 for biochar, 22.7 Mg ha^-1 for biochar plus N, 22.7 Mg ha^-1 for cover crops, and 22.1 Mg ha^-1 for control. Some of the reasons that may explain the lack of treatment effects may include: 1) the short period of time after experiment start, 2) low rate of biochar application, 3) initial high fertility of the soil, and 4) relatively the high clay content of the soil. We hypothesized that the application of biochar could rapidly change the SOC pools, but this was not support by the data. Overall, biochar application at low rates and cover crop mixtures after one year of management may not significantly alter soil C storage and other soil properties.