Effect of Two Biochar Types On Nitrous Oxide Emissions In a Commercial Vineyard.

Biochar, pyrolyzed organic biomass, has the potential to reduce the emissions of nitrous oxide (N₂O), by affecting soil hydrology, microbial habitats, and the availability of nitrate and carbon substrates.  Through quantification of soil physical, structural, and hydrologic changes, coupled with frequent sampling of N₂O, inorganic N, and dissolved organic C and N, this study attempts elucidate the underlying factors and mechanisms for N₂O flux in response to biochar amendment. A walnut biochar (WC) produced at ~950°C and pine chip biochar (PC) produced at ~550°C were incorporated at a rate of 10t/ha to a vineyard in the fall of 2010.  All analyses were performed on samples taken from two functional locations within each plot: berm (directly beneath vines) and alley.  Here, we report results from the initial incorporation and first growing season.  Berm cumulative N₂O emissions were highest in control plots, in contrast alley cumulative emissions were significantly higher in WC plots and higher yet in PC plots. During the winter season water filled pore space in the control was significantly higher than either of the biochar treatments in both the berm and alley, suggesting increased macroporsity and saturated flow. Dissolved organic carbon was significantly lower in the berm control plots immediately following incorporation, but the trend did not persist.  Nitrate levels declined significantly over the winter months, with no significant differences between treatments.  PC plots showed a trend of higher ammonium levels throughout the growing season.  Following berm fertilization biochar plots showed increased NH₄⁺ retention relative to the control, however this did not correlate to changes in N₂O emissions.  While the data represent only preliminary results, they suggest that biochar is indeed influencing the saturated hydraulic flow and inorganic N dynamics and therefore N₂O fluxes.