Nitrous Oxide Production and Reduction in Seasonally‐Flooded Cultivated Peatland Soils

Core Ideas We quantified N 2 O production and reduction for cultivated intermittently flooded peatland soils. Labile organic C limited N 2 O production and reduction. High residual NO 3 − in soils inhibited N 2 O reduction. N 2 O emissions were inversely proportional to land management intensity and decreased in the order of uncultivated, turfgrass, vegetable, and sugarcane soils. Biogeochemical controls of N 2 O production and reduction during denitrification in cultivated and intermittently flooded peatland soils are poorly understood. Soils from sugarcane ( Saccharum spp.), vegetable, turfgrass, and uncultivated subtropical peatlands in the Everglades Agricultural Area (EAA) were studied to elucidate influence of land use on N 2 O production and reduction. Under ambient soil conditions, intensively managed, tilled soils (sugarcane and vegetable) had 1.5 to 4 times lower N 2 O production and reduction than turfgrass soils. Uncultivated soils had 130 to 270% higher N 2 O production than tilled soils but had similar N 2 O reduction compared with tilled soils. A lower ratio of N 2 O reduction to production was observed for uncultivated soils compared to other land uses. Net N 2 O production was highest for uncultivated soils and decreased in the order of turfgrass, vegetable, and sugarcane soils. For all land uses, N 2 O production was limited by electron donors (labile organic C) but not by electron acceptors (NO 3 − ). Depletion of labile organic C through long‐term soil oxidation after drainage resulted in limited availability of this energy source for denitrifying microorganisms. In addition, high residual NO 3 − resulting from organic N mineralization and inorganic fertilizer additions inhibited N 2 O reduction. Our results suggest that sugarcane production is likely to reduce N 2 O emissions from the EAA compared with other current land uses. Management practices with addition of labile organic C to the EAA soils may possibly result in N 2 O emission pulses because of the greater stimulation of labile organic C on N 2 O production than on N 2 O reduction.