Nitrous oxide (N2O) emissions in response to increasing fertilizer addition in maize (Zea mays L.) agriculture in western Kenya

摘要

National and regional efforts are underway to increase fertilizer use in sub-Saharan Africa, where attaining food security is a perennial challenge and mean fertilizer use in many countries is < 10 % of nationally recommended rates. Increases in nitrogen (N) inputs will likely cause increased emissions of the greenhouse gas nitrous oxide (N2O). We established experimental plots with different rates of N applied to maize (Zea mays) in a field with a history of nutrient additions in western Kenya and measured N2O fluxes. Fertilizer was applied by hand at 0, 50, 75, 100, and 200 kg N ha(-1) in a split application on March 22 and April 20, 2010. Gas sampling was conducted daily during the week following applications, and was otherwise collected weekly or biweekly until June 29, 2010. Cumulative fluxes were highest from the 200 kg N ha(-1) treatment, with emissions of 810 g N2O-N ha(-1); fluxes from other treatments ranged from 620 to 710 g N2O-N ha(-1), but with no significant differences among treatments. Emissions of N2O during the 99-day measurement period represented < 0.1 % of added fertilizer N for all treatments. Though limited to a single year, these results provide further evidence that African agricultural systems may have N2O emission factors substantially lower than the global mean