Chemical Reactions of Nitrites in Acid Soils

Abstract

Abstract Sodium nitrite at a concentration of 400 ppm N was added to samples of 4 soils and the reaction products studied over several days. Nitrogen (N 2 ) and nitrous oxide (N 2 O) gas evolutions were determined by means of a gas chromatograph. The higher oxides of N (NO + NO 2 ) were absorbed in alkaline KMnO 4 and then analyzed. Nitrogen gas (N 2 ) was rapidly released by the acid soils but not by a cation resin used as an artificial medium. Minor amounts of N 2 O were detected. All products were the result of chemical rather than microbiological processes. The NO 3 ‐ and higher oxides formed are almost certainly the result of HNO 2 decomposition reactions. The processes leading to the formation of N 2 and N 2 O remain in doubt. About 40% of the NO 2 ‐ remaining after the gaseous atmosphere was flushed free of N 2 was converted to N 2 gas in 24 hours in the Bath silt loam (pH 4.6). In the less acid Fort Collins sandy clay loam (pH 5.6) and Walla Walla silt loam (pH 5.6) the comparable values were 12% and 9.5% respectively. From the Bath silt loam, 36% of the NO 2 ‐ was found in the KMnO 4 trapping solutions, but this required 96 hours. In the same time interval the amounts of these nitrogen oxides evolved and trapped in the systems for the Fort Collins and Walla Walla soils were 26% and 17%.