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

We measured fluxes of N2O, CH4 and CO2 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 CO2 emissions, but significantly increased the emissions of N2O and lowered the uptake of atmospheric CH4. Daily average N2O emissions from the fertilized soils were 8–600 times higher (12–74 μg N2O-N•m−2•h−1) than daily average N2O emissions from control soils (0.02–4.0 μg N2O-N•m−2•h−1). Daily average CH4 uptake by the fertilized soils were 5–20 times lower (0.001–0.007 mg CH4-C•m−2•h−1) than daily average CH4 uptake by control soils (0.015–0.035 mg CH4-C•m−2•h−1). We also measured the relative activities of the bacteria populations that were responsible for CH4 oxidation in the control and fertilized soils. Results from these measurements suggest that fertilization shifted the relative activities of the CH4 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 CH4 uptake by the fertilized soils.