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

Abstract

Core Ideas We quantified N2O production and reduction for cultivated intermittently flooded peatland soils. Labile organic C limited N2O production and reduction. High residual NO3− in soils inhibited N2O reduction. N2O emissions were inversely proportional to land management intensity and decreased in the order of uncultivated, turfgrass, vegetable, and sugarcane soils. Biogeochemical controls of N2O 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 N2O production and reduction. Under ambient soil conditions, intensively managed, tilled soils (sugarcane and vegetable) had 1.5 to 4 times lower N2O production and reduction than turfgrass soils. Uncultivated soils had 130 to 270% higher N2O production than tilled soils but had similar N2O reduction compared with tilled soils. A lower ratio of N2O reduction to production was observed for uncultivated soils compared to other land uses. Net N2O production was highest for uncultivated soils and decreased in the order of turfgrass, vegetable, and sugarcane soils. For all land uses, N2O production was limited by electron donors (labile organic C) but not by electron acceptors (NO3−). 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 NO3− resulting from organic N mineralization and inorganic fertilizer additions inhibited N2O reduction. Our results suggest that sugarcane production is likely to reduce N2O 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 N2O emission pulses because of the greater stimulation of labile organic C on N2O production than on N2O reduction.