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This article in SSSAJ

  1. Vol. 36 No. 3, p. 465-472
    Received: July 14, 1971
    Published: May, 1972



Nitrogen Mineralization Potentials of Soils1

  1. George Stanford and
  2. S. J. Smith2



Net mineralization of N in 39 widely differing soils was determined over a 30-week period at 35C, using incubation intervals of 2, 2, 4, 4, 4, 6, and 8 weeks. Mineral N was leached from the soils before the first incubation and following each of seven incubations by means of 0.01M CaCl2 and a minus-N nutrient solution. Soil water contents were adjusted by applying suction (60 cm Hg), and losses of water during incubation under aerobic conditions were negligible. With most soils, cumulative net N mineralized was linearly related to the square root of time, t½. The pH of soils changed very little in the course of 30 weeks' incubation. Because of the generally consistent results, the data were employed in calculating the N mineralization potential, No, of each soil, based on the hypothesis that rate of N mineralization was proportional to the quantity of N comprising the mineralizable substrate. Values of No ranged from about 20 to over 300 ppm of air-dry soil. The fraction of total N comprising No varied widely (5 to 40%) among soils. Mineralization rate constants did not differ significantly among most of the soils. The most reliable estimate of the rate constant, k was .054 ± .009 week-1. The time required to mineralize one-half of No, t½, was estimated to be 12.8 ± 2.2 weeks. Results suggest that the forms of organic N contributing to No were similar for most of the soils.

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