Gaseous Nitrogen Evolution During Nitrification of Ammonia Fertilizer and Nitrite Transformations in Soils1
- C. J. Smith and
- P. M. Chalk2
The biological oxidation of NO2- is inhibited when alkaline-hydrolyzing N fertilizers are band-applied to soils, and NO2- may accumulate. Nitrogenous gases can be evolved with NO2- is added to soil. The aim of the work described here was to determine if gaseous-N losses could occur via chemical transformations of NO2- during nitrification in soils treated with NH3 fertilizer.
Evolution of N2, N2O, and NO + NO2 occurred during nitrification in three soils treated with aqueous NH3. 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, NO2- did not accumulate to more than 13 µg N/g of soil, but substantial N2 emission was measured. Addition of the nitrification inhibitor, nitrapyrin, with the fertilizer, prevented NO2- accumulation without preventing nitrification. This treatment prevented N2O evolution and markedly reduced loss of N2 and NO + NO2.
Evolution of N2, N2O, and NO + NO2 occurred in the three soils following NO2- addition. Loss of N2 was very sensitive to soil pH, and markedly increased with increasing acidity. However, N2 was readily evolved when soil pH was slightly alkaline. Evolution of NO + NO2 was inversely related to pH, but N2O 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 NH3 and NO2- treatments, strongly suggest that similar processes were operating. Gaseous-N evolution was similar in γ-irradiated and nonirradiated soils treated with NO2-. These results, together with the effect of nitrapyrin, suggest that gaseous-N losses can occur via chemical transformations of NO2-, when the competitive biological oxidation of NO2- by Nitrobacter is inhibited.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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