Nitrous oxide emission from upland soil amended with different animal manures

The nitrous oxide (N2O) emission of from arable soil following the application of manure is expected to vary by different animal manure types used. This study was conducted to determine the relationship between the type of animal manure used to amend soil and the amount of N2O emitted during the cultivation of sweet potato (Ipomoea batatas). An additional objective was to study the characteristics of nitrogen (N) and carbon (C) in different animal manures. Composted manures from chickens, cows, and pigs were applied to the soil at rates of 0, 10, and 20 Mg ha−1, respectively. The availability and concentration of N and C varied by manure type. The concentration of NH4+ was greater in pig manure (4638 mg kg−1) than in chicken (551 mg kg−1) and cow manure (147 mg kg−1). The mean cumulative N2O emission rate across soil application rates was also the highest with pig manure (11.9 kg ha−1 year−1), followed by chicken and cow manure, with emission rates of 10.8 and 10.1 kg ha−1 year−1, respectively. The majority of N2O measured during the sweet-potato-growing season was produced from aerobic nitrification. Dissolved organic carbon (DOC) concentrations in animal manures did not affect cumulative N2O emission rates, and no significant relationship was observed throughout the growing season between the concentration of DOC in soil and daily N2O emission. Cumulative N2O emission rates depended on the type of animal manure and might be governed by NH4+ concentration, rather than by total N concentration in animal manure type.