Nitrous Oxide Production and Consumption during Denitrification in Peatlands Under Different Flooding and Draining Cycles.

Nowadays, around 10-20% peatlands have been drained for agricultural uses. The drainage increases soil aeration and organic matter oxidation, resulting in soil subsidence and high carbon (C) loss as carbon dioxide (CO₂) from peatlands into atmosphere. To safeguard the valuable peatlands and mitigate global climate change, they should be protected from further subsidence and C loss. Flooding-draining cycles accommodated to crop rotation could be an option to reduce the environmental impacts caused by drainage. However, the alternate draining and flooding could increase nitrous oxide (N₂O) emission, which has 298 times global warming potential of CO₂. Denitrification is a major process of N₂O production and the only biological pathway of N₂O consumption in soils. Quantifying production and consumption of N₂O during denitrification under different flooding-draining cycles could be essential to understand N₂O emission.

A core study was conducted on soil cores (40 cm in depth, 10 cm in diameter) collected from the Everglades Agricultural Area in south Florida. Six different hydrologic treatments: continuously flooded, continuously drained, and 4 cyclically treated with various draining and flooding periods, were included. Greenhouse gas fluxes from each core were measured 2-4 times per week for 24 weeks. Soil cores under cyclic treatments were destructively sampled at the end of both drained and flooded periods of the last cycle to the depths of 0-10, 10-30, and 30-40 cm. Soil cores under the continuously flooded and drained treatment were sampled at the end of 24 weeks to the same depths. All soil samples were analyzed for ammonium (NH₄⁺), nitrate (NO₃^-), microbial biomass carbon (MBC), and denitrifying enzyme activity (DEA). The soil samples collected under drained condition were analyzed for the N₂O production and consumption using the acetylene block method.