Nitrous Oxide Emission from an Agricultural Soil Fertilized with Liquid Swine Waste or Constituents

Large scale swine production facilities that land‐apply liquid waste are rapidly expanding in the southeastern USA. This study evaluated controls on N 2 O emission in a Goldsboro loamy sand (fine‐loamy thermic, aquic Typic Paleudult) receiving field in North Carolina that was planted to winter wheat ( Triticum aestivum L.). Two experiments were conducted in April–May 1997 where field plots were fertilized with liquid swine waste, individual chemical constituents of waste (NH 4 , available C), NO 3 , or deionized water. Temporal changes in N 2 O efflux and soil physicochemical properties were assessed over 8 and 11 d.. Treatments that included N (75–165 kg ha −1 ) showed N 2 O fluxes exceeding 4000 μg N 2 O–N m −2 h −1 within 1 d of fertilization, but emissions declined to prefertilization values (∼10–25 μg N 2 O–N m −2 h −1 ) within a few days as soils drained. Treatments that did not include N (deionized water, glucose) showed no increase in N 2 O emission over unfertilized controls. Time‐integrated N 2 O emission was significantly lower for plots amended with swine waste (8.5 mg N 2 O–N m −2 ) compared with plots comparably fertilized with NH 4 –N plus glucose‐C (20.8 mg N 2 O–N m −2 ), suggesting that some component of the waste adversely affected the microbial N cycling community. The immediate increase in N 2 O emission following fertilization and accumulation of NO 3 –N without lag indicated that repeated fertilization throughout the growing season maintained active and responsive nitrifying and denitrifying communities. Percentage fertilizer loss to N 2 O to the point where fluxes had returned to prefertilization values was low, <1.0%. However, simulated rainfall gave pulsed N 2 O emission from denitrification of accumulated NO − 3 –N, indicating that further emissions will occur with an increase in soil moisture.