Effect of Acidity on Denitrifcation and Nitrous Oxide Evolution from Atlantic Coastal Plain Soils

Abstract

Abstract The effect of acidity on denitrification and nitrous oxide production in six soils from the Atlantic Coastal Plain was estimated using laboratory incubations of flooded soil for periods up to 21 d. Increased denitrification rates were associated with a decrease in acidity in all soils but most of the effect occurred above pH 6.5. Some accumulation of NH + 4 ‐N occurred in all soils and was positively correlated to the NO ‐ 3 ‐N lost from the system. Small quantities of NO ‐ 2 ‐N were formed in all soils. Larger amounts of NO ‐ 2 ‐N were found at pH 5.0 and 4.7 for two soils. Nitrite‐N accumulation corresponded to the release of large quantities of N 2 O suggesting a possible relationship between NO ‐ 2 ‐N accumulation and N 2 O production. Nitrous oxide evolved, as a percentage of NO ‐ 3 ‐N lost, increased with increasing acidity with maximum N 2 O being evolved at pH values ≤5.8. Above pH 5.8, evolution of N 2 O virtually ceased. Since all six Coastal Plain soils are generally <pH 5.8, a high percentage of nitrogen being lost from these soils through denitrification is as N 2 O.