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This article in SSSAJ

  1. Vol. 71 No. 4, p. 1233-1239
    Received: July 20, 2006

    * Corresponding author(s): ZebarthB@agr.gc.ca
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Evaluation of Some Indices of Potentially Mineralizable Nitrogen in Soil

  1. M. Sharifia,
  2. B. J. Zebarth *a,
  3. D. L. Burtonb,
  4. C. A. Grantc and
  5. J. M. Cooperb
  1. a Agriculture and Agri-Food Canada, Potato Research Centre, P.O. Box 20280, Fredericton, NB, Canada E3B 4Z7
    b Dep. of Environmental Science, Nova Scotia Agricultural College, P.O. Box 550, 21 Cox Rd., Truro, NS, Canada B2N 5E3
    c Agriculture and Agri-Food Canada, Brandon Research Centre, Grand Valley Rd., Brandon, MB, Canada R7A 5Y3


A series of soil N mineralization indices were evaluated using 153 samples chosen from arable fields representing a wide range of soil types, management practices, and climatic zones. These indices were compared against potentially mineralizable N (N0) determined by aerobic incubation at 25°C for 24 wk. Three different pools of mineralizable N were recognized: Pool I, the mineralization flush on rewetting in the first 2 wk; Pool II, gross N mineralization in the next 22 wk; and Pool III, the potentially mineralizable N, predicted from the fitted curve, that did not mineralize during the incubation period. Pool I was highly correlated with CaCl2–N, KCl-NH4, and KCl-NO3, which extract soil mineral N. Pool III was significantly correlated with ultraviolet absorbance of NaHCO3 extract at 205 and 260 nm (NaHCO3–205 and −260), Illinois soil N test, NaOH direct-distillation N, and hot KCl-NH4, which mostly extract hydrolyzable organic N. All indices except the mineral N based methods, phosphate-borate buffer method, and microbial biomass C were significantly related to N0, which includes both Pools II and III. The NaHCO3–260, NaOH direct-distillation N, and Illinois soil N test had the highest correlations with N0 (r 2 = 0.74, 0.61, and 0. 51, respectively). Total organic C and N represent long-term changes in N0 and were almost as effective in predicting N0 as the other indices (r 2 = 0.60 and 0.67, respectively); however, they would be expected to be less sensitive to short-term changes in N0 due to changes in soil management practices and history.

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