Nitrous Oxide and Methane Fluxes from Smallholder Farms: A Scoping Study in the Anjeni Watershed

While agricultural practices are widely reported to contribute to anthropogenic greenhouse gas (GHG) emissions, there are only limited measurements available for emission rates in the monsoon climate of the African continent. We conducted a scoping study to measure nitrous oxide (N2O-N) and methane (CH4) emission rates from 24 plots constructed on smallholder agricultural farms along the slope catena of three transects in the sub-humid Anjeni watershed in the Ethiopian highlands. Greenhouse gas flux samples were collected in 2013, before, towards the end, and after the rainy monsoon phase. At each location, three plots were installed in groups: two plots grown with barley (one enriched with charcoal and the other without soil amendment) and lupine was grown on the third plot without any soil amendment. Preliminary study results showed that nitrous oxide emission rates varied from −275 to 522 μg·m−2·h−1 and methane emissions ranged from −206 to 264 μg·m−2·h−1 with overall means of 51 and 5 μg·m−2·h−1 for N2O-N and CH4, respectively. Compared with the control, charcoal and lupine plots had elevated nitrous oxide emissions. Plots amended with charcoal showed on average greater methane uptake than was emitted. While this study provides insights regarding nitrous oxide and methane emission levels from smallholder farms, studies of longer durations are needed to verify the results.