Mineralization of nitrite fixed by soil organic matter

The biological availability of [¹⁵N]labelled nitrite fixed by the organic matter of two acid soils was determined by laboratory incubation and pot experiments. Fixed-N was resistant to mineralization, but was more readily available than the indigenous organic-N. Approximately 20% of the fixed-N was recovered as inorganic-N after 70 days of incubation, or was recovered in the roots and three cuttings of rye-grass grown for 197 days, whereas less than 10% of the indigenous organic-N was recovered. With increasing time, the fixed-N becomes more resistant to mineralization, becoming similar to the indigenous organic-N.