Nitrous oxide production and flux from soil under sod following application of different nitrogen fertilizers

Concern over contribution of nitrous oxide (N2O) to global warming and stratospheric ozone depletion has prompted measurement of nitrous oxide (N2O) emissions from agricultural soils and study of controlling factors. The objectives of this study were (1) to measure the magnitude of N2O emissions from application of (NH4)(2)SO4, Ca(NO3)(2) or urea teach at 100 kg N/ha) to a Kentucky bluegrass (Poa pratensis L.) stand, and (2) to compare flux of N2O from the surface measured with covers to N2O production and denitrification in soil cores collected at a depth of 2.5 -7.5 cm. Water, NH4+ and NO3 contents of soil cores were also measured. Application of all three fertilizers increased N2O production by soil cores, and N2O flux from covers. The two measurements differed in temporal pattern and magnitude. Flux of N2O from the soil surface is a more complex and variable process than N2O production in a specific soil layer. The possibility of increased N2O production with urea requires further investigation under more controlled conditions. Nitrification of NH4+ appeared to be the principal source of N2O.