Nitrous and nitrogen oxide emissions from turfgrass receiving different forms of nitrogen fertilizer

The use of N fertilizer in agriculture is considered an important source of atmospheric N2O and NO,. Choice of fertilizer type and management has been considered a method fur mitigating these emissions. Micrometeorological methods were used to study the effect of inorganic N fertilizers urea (U), slow-release urea (SRU), and ammonium nitrate (AN) on fluxes of N2O, NO, and NO2 from turfgrass field plots during three seasons, from 1995 to 1997 (total of 353 d of measurement). Daily average fluxes after fertilizations reached a maximum of 2091 ng N2O-N m(-2) s(-1) after the first fertilization with AN in 1996. The fertilized plots had significantly higher emissions (P < 0.05) than the control plot, and the highest N2O emissions were from AN in 1995 and 1996, and from SRU in 1997. Daily fluxes of up to 186 ng NO-N m(-2) s(-1) were measured within 1 wk following fertilization in 1997. The U plot had significantly higher NO emissions during all seasons compared with other fertilized plots. Fluxes of NO, during 1996 and 1997 were consistently downward, indicating that turfgrass was acting as a sink for NOx. NO2 uptake seemed to be directly related to NO emissions, and the U plot presented the highest NO2 uptake. Urea-based fertilizers seem to minimize N2O emissions, although long-term effects of SRU still need to be studied. The higher NO emissions from U-based fertilized plots do not seem to be a problem, since NOx uptake occurred at higher rates than NO emission.