Belowground Contributions from Dryland Switchgrass and No-till Maize to Soil Organic C and N after 9 Years of N and Harvest Treatments.

Plant contributions to belowground biomass and soil C stocks are important for developing accurate bioenergy lifecycle models. Switchgrass (Panicum virgatum L.) is a native perennial, cellulosic biofuel feedstock with greater root production compared to corn (Zea mays L.,) and potentially contributes to greater SOC sequestration. Field management (nitrogen (N) fertilizer rate and harvest management) could influence bioenergy crop root biomass allocation and subsequently, SOC and soil properties. We examined plant belowground biomass, C, N and soil nutrients in a 9 year non-irrigated study of N fertilizer rate (0, 60, 120, and 180 kg N ha^-1) and harvest management in Mead, NE. Switchgrass was harvested with one pass in either Aug. or post-frost and 50% or no stover was removed for no-till corn. Switchgrass had greater root biomass C & N (6.39, 0.96 Mg ha^-1) throughout the profile compared to corn (1.30, 0.58 Mg ha^-1) and a higher root C:N ratio (82.63 vs. 29.41), indicating greater recalcitrant belowground C input beneath switchgrass. Both N fertilizer and harvest management altered rooting dynamics in both species to a depth of 150cm. Nine years of residue removal reduced corn root biomass C and N. Agricultural management of bioenergy crops will influence belowground plant allocation and C dynamics in this mesic system.