Nitrous and nitric oxide emissions during nitrification and denitrification from manure-amended soil in the laboratory

Denitrification and nitrification processes in soil produce significant amounts of atmospheric N 2 O and NO. Laboratory experiments were designed to measure N 2 O and NO emissions from an agricultural soil shortly after manure addition. Nitrous oxide emissions were higher from soil following addition of manure slurries than following addition of composted manure. Emissions of both N 2 O and NO were highest between 1 and 4 d after manure addition. Nitrous oxide emission following manure application was the result of both denitrification and nitrification, which occurred simultaneously in soil. Denitrification was a major producer of N 2 O because both denitrification rates and N 2 O emission increased dramatically at higher soil-moisture contents and increased manure concentration. Nitric oxide production occurred during nitrification. Nitrous oxide emitted during the 6 d after manure addition ranged from 0.025 to 0.85% of the manure N. Nitric oxide emissions were approximately 0.26% of the amount of added manure N.Key words: Nitrous oxide, nitric oxide, manure, denitrification, nitrification