Effect of Oxidation of Soil Organic Matter on Water Quality: Role of Nitrification and Denitrification

摘要

Since mineral nitrogen produced in Histosols has a significant effect on regional water quality, nitrification and denitrification and the effect of the physical and chemical environment on these reactions were studied in Pahokee muck, a drained Histosol. Highest potential denitrification rates were detected in cultivated fields. These rates were about 3-fold that of a soil from a fallow field. Nitrite accumulated in low concentrations in the soils as a result of denitrification. Denitrification was limited by carbon in uncultivated soils, but not in the soils from the sugarcane or grass fields. Oxygen was limiting to denitrification in drained soils since during flooding the denitrification capacity and denitrifier populations increased, while soil nitrate levels decreased about 80 percent. Although large populations of heterotrophic nitrifiers were found in Pahokee muck, studies of population densities and changes in soil that had been heated to kill the autotrophic nitrifiers but not the heterotrophs demonstrated that autotrophic nitrifiers were the sole population responsible for nitrification.