Gaseous Nitrogen Evolution During Nitrification of Ammonia Fertilizer and Nitrite Transformations in Soils

Abstract The biological oxidation of NO 2 ‐ is inhibited when alkaline‐hydrolyzing N fertilizers are band‐applied to soils, and NO 2 ‐ may accumulate. Nitrogenous gases can be evolved with NO 2 ‐ is added to soil. The aim of the work described here was to determine if gaseous‐N losses could occur via chemical transformations of NO 2 ‐ during nitrification in soils treated with NH 3 fertilizer. Evolution of N 2 , N 2 O, and NO + NO 2 occurred during nitrification in three soils treated with aqueous NH 3 . Losses occurred when measured soil pH was > 7.5. The highest gaseous‐N loss amounted to 16.5% of applied‐N (1156 µg N applied/g of soil) in a calcareous soil incubated for 28 days at 30°C. Nitrogen was the major gaseous form of N evolved in all soils. In two soils, NO 2 ‐ did not accumulate to more than 13 µg N/g of soil, but substantial N 2 emission was measured. Addition of the nitrification inhibitor, nitrapyrin, with the fertilizer, prevented NO 2 ‐ accumulation without preventing nitrification. This treatment prevented N 2 O evolution and markedly reduced loss of N 2 and NO + NO 2 . Evolution of N 2 , N 2 O, and NO + NO 2 occurred in the three soils following NO 2 ‐ addition. Loss of N 2 was very sensitive to soil pH, and markedly increased with increasing acidity. However, N 2 was readily evolved when soil pH was slightly alkaline. Evolution of NO + NO 2 was inversely related to pH, but N 2 O loss was highest in the most alkaline soil (pH 8.4). The marked similarities within individual soils of the patterns of gaseous‐N losses obtained for NH 3 and NO 2 ‐ treatments, strongly suggest that similar processes were operating. Gaseous‐N evolution was similar in γ‐irradiated and nonirradiated soils treated with NO 2 ‐ . These results, together with the effect of nitrapyrin, suggest that gaseous‐N losses can occur via chemical transformations of NO 2 ‐ , when the competitive biological oxidation of NO 2 ‐ by Nitrobacter is inhibited.