Fixation and Loss of Nitrogen During Transformations of Nitrite in Soils1
- C. J. Smith and
- P. M. Chalk2
When alkaline-hydrolyzing N fertilizers are band-applied to soils, the biological oxidation of NO2- is inhibited and NO2- may accumulate. Nitrite can react chemically with soil organic matter and become fixed, and at the same time nitrogenous gases can be evolved. The aim of the work described here was to study mechanisms of gaseous-N formation using 15NO2- as a tracer, and to define the relationship between fixation and loss of N.
Fixation of Na15NO2 in five soils varying in pH and organic C content ranged from 0.6 to 36% of applied NO2-, while the 15N not recovered varied from 6 to 53%. A significant positive correlation was found between 15N fixed and 15N not recovered in the five soils, sampled after 1, 2, and 3 days of incubation.
The 15N enrichment of NO + NO2 evolved from three γ-irradiated soils treated with Na15NO2 was only slightly less than the atom % 15N of added NO2-, and the rate of evolution increased as the pH of the soils decreased. These data suggest that NO + NO2 was derived from the self-decomposition of HNO2. Approximately equal amounts of indigenous soil N and added NO2--N reacted to form N2, indicating that a Van Slyke-type reaction may have been partly responsible. Differences in the atom % 15N2 between soils suggested that more than one loss mechanism was operating, and that their relative importance may have been determined by soil pH. Nitrogen-15 balance data showed that another nitrogenous gas, in addition to N2O, was evolved.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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