Nitric Oxide Emissions from an Ultisol of the Humid Tropics Under Maize Groundnut Rotation

At the Universiti Putra Malaysia experimental farm, a field experiment was conducted to examine the influence of amounts and sources of nitrogen on the nitrous oxide emission from a maize groundnut crop rotation. The study was conducted from November 1998 to November 1999. The treatments included: recommended inorganic N plus crop residues, recommended inorganic N only, and a half-dose of recommended inorganic N plus crop residues plus chicken manure. Nitrous oxide fluxes were measured for the groundnut growth period, the fallow period after groundnut, the subsequent maize growth period, and the fallow period after maize. Results showed that N sub(2)O emission was enhanced by the application of chicken manure, but under the right conditions, the mineral N applied or mineralized from organic sources could be retained for an extensive period of time in the soil. Overall, the annual N sub(2)O emissions were small relative to N inputs, with up to 99% or more of the applied N remaining in the crop soil water system.