NITROUS-OXIDE PRODUCTION THROUGHOUT THE YEAR FROM FERTILIZED AND MANURED MAIZE FIELDS

Two field sites on a loam soil were established to monitor N//2O concentration in the soil atmosphere and rate of emission from the soil surface. Fluctuations in N//2O emissions from the two sites were temporally similar, and differed only in magnitude with Site A (no additional fertilizer), emitting about 3. 6 kg N//2O-N ha** minus **1 yr** minus **1 and Site B about 5. 2 kg N//2O-N ha** minus **1 yr** minus **1, or about 2% of the N applied. Most of the N//2O was emitted between mid-June and the end of July when the soil was warm and NH//4** plus -N was present, and at spring thaw when soils were cold and near water-saturated. High N//2O emissions during the growing season occurred following precipitation events, and hence were associated with high soil water and probably with the initiation of soil drying. Nitrous oxide production was continuous during winter months, presumably a result of denitrification. Additional study results are discussed.