Catherine E. Stewart1, Karolien Denef2, Jorin Botte2, Jesus D. Gomez3, Jiyong Zheng4 and M. Francesca Cotrufo2, (1)USDA-ARS, Fort Collins, CO (2)Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO (3)Soil Department, Universidad Autonoma Chapingo, Chapingo, Mexico (4)State Key Laboratory of Soil Erosion and Dyland Farming on the Loess Plateau, Northwest A & F University, Yangling, China
Biochar addition to soil may mitigate GHG emissions, sequester recalcitrant C and increase microbial populations all of which benefit agroecosystems. However, after biochar additions net GHG emissions (CO2, N2O, and CH4) have been positive, neutral, or negative depending on the biochar feedstock, pyrolysis temperature, as well as soil type. We determined the effect of biochar addition rates (0, 1, 5, 10, and 20% by weight) on GHG emissions and microbial community dynamics from four soils varying from a clay to a sand on during a 2 year incubation. To trace CO2 source, we added C3 biochar (oak, pyrolyzed at 550°C) to C4 soils and measured CO2, N2O, and CH4, and total and relative abundance of phospholipid fatty acids (PLFA) and 13C signatures in CO2 and PLFAs. Biochar addition initially suppressed CO2, but after 3-4 months, biochar-derived CO2 was proportional to biochar addition rate. In all soils, N2O emissions were suppressed, although the reduction to addition rate varied from 20% to 94% depending on soil type. Biochar contribution to total respiration fluxes varied with soil type and the amount of biochar added, suggesting an interaction with microbial activity and the possible need for the microbial community to adapt to the new C source. We will report microbial community structure and abundance as affected by biochar addition rate and soil type, and discuss them in the context of the observed changes in GHG efflux.