Intra-annual changes in biomass, carbon, and nitrogen dynamics at 4-year old switchgrass field trials in west Tennessee, USA

Switchgrass is a potential bioenergy crop that could promote soil C sequestration in some environments. We compared four switchgrass cultivars on a well-drained Alfisol to test for differences in biomass, C, and N dynamics during the fourth growing season. There was no difference ( P > 0.05) among cultivars and no significant cultivar × time interaction in analyses of dry mass, C stocks, or N stocks in aboveground biomass and surface litter. At the end of the growing season, mean (±SE) aboveground biomass was 2.1 ± 0.13 kg m −2, and surface litter dry mass was approximately 50% of aboveground biomass. Prior to harvest, the live root:shoot biomass ratio was 0.77. There was no difference ( P > 0.05) among cultivars for total biomass, C, and N stocks belowground. Total belowground biomass (90 cm soil depth) as well as coarse (≥1 mm diameter) and fine (