Soil Organic Carbon Changes for Switchgrass Farms in East Tennessee, USA
D. K. Toliver, B. C. English, D. D. Tyler, J. Lee, R. J. Menard, and J. C. Walton.  2018.  Soil Systems.  (in press)

Abstract:
Much attention has occurred in switchgrass¡¯ potential for conversion to cellulosic ethanol and its ability to sequester soil organic carbon (SOC). Soil samples from switchgrass farms in east Tennessee were collected at depths of 0-5, 15-30, 30-60, and 60-90 cm and tested for SOC over a four-year period (2008-2011). Results showed no differences (P¡Ý0.10) in SOC from 2008-2011. However, when comparing the initial samples to year 4, SOC decreases ranging from .04 to .47 t ha-1 were observed in the 5-10 and 10-15 cm soil depths. A significant amount of carbon was sequestered in the 90-120 cm depth in the same four-year time frame. Following three full growing seasons, switchgrass¡¯ potential to sequester carbon comes at deeper soil depths due to its vast root structure. Greater levels of carbon were present in soil previously no-tilled compared to those previously under conventional tillage, however, neither gained or lost a significant amount of SOC by year four. Alfisols were the only taxonomic category that had a significant increase in SOC by year four. Green beans were the only previously produced crop that had a significant positive effect on sequestering carbon. Increases in switchgrass yield were correlated to SOC.