Effects of nitrogen fertilization on the fluxes of N2O, CH4, and CO2 from soils in a Florida slash pine plantation

We measured fluxes of N 2 O, CH 4 and CO 2 from control and urea-nitrogen fertilized soils of a mature slash pine (Pinuselliottii var. elliottii Englem.) plantation in Alachua County, Florida. The fertilization did not affect CO 2 emissions, but significantly increased the emissions of N 2 O and lowered the uptake of atmospheric CH 4 . Daily average N 2 O emissions from the fertilized soils were 8–600 times higher (12–74 μg N 2 O-N•m −2 •h −1 ) than daily average N 2 O emissions from control soils (0.02–4.0 μg N 2 O-N•m −2 •h −1 ). Daily average CH 4 uptake by the fertilized soils were 5–20 times lower (0.001–0.007 mg CH 4 -C•m −2 •h −1 ) than daily average CH 4 uptake by control soils (0.015–0.035 mg CH 4 -C•m −2 •h −1 ). We also measured the relative activities of the bacteria populations that were responsible for CH 4 oxidation in the control and fertilized soils. Results from these measurements suggest that fertilization shifted the relative activities of the CH 4 oxidizing bacteria from those dominated by methanotrophs in the control soils to those dominated by nitrifying bacteria in the surface (0–2 cm) of the fertilized soils. The shift in relative activities of these bacteria may have been responsible for the lower CH 4 uptake by the fertilized soils.