Ammonia and nitrous oxide emissions from a field Ultisol amended with tithonia green manure, urea, and biochar

Short-term mitigation of ammonia (NH3) and nitrous oxide (N2O) emissions by biochar soil amendments has been reported, but limited knowledge of the mechanisms, particularly those associated with long term changes, remain relatively unknown. In order to investigate potential mechanisms and residual effect of biochar on NH3 and N2O emission, a 3-year field trial was set up on an Ultisol in western Kenya with a three-replicate full factorial treatment structure. The factors investigated include the following: biochar (from eucalyptus wood, pyrolyzed at 550 °C, applied once before the start of the experiment at either 0 or 2.5 t ha1); tithonia green manure applied at the start of each season at either 0, 2.5, or 5.0 t ha1; mineral nitrogen (N) (as urea applied each season at either 0 or 120 kg N ha1). NH3 as well as N2O emission and water-filled pore space (WFPS) were monitored throughout the 3 years.