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Soil Science Society of America Journal Abstract -

Effects of Terpenoids on Nitrification in Soil


This article in SSSAJ

  1. Vol. 52 No. 6, p. 1630-1633
    Received: Dec 18, 1987

    * Corresponding author(s):
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  1. J. M. Bremner and
  2. G. W. McCarty
  1. Department of Agronomy, Iowa State Univ., Ames, IA 50011



It has recently been hypothesized that vegetation in ponderosa pine (Pinus ponderosa Dougl.) ecosystems inhibits nitrification in these systems by releasing volatile terpenoids that retard oxidation of NH+4 by nitrifying microorganisms. This hypothesis is based largely on observations that exposure of a ponderosa pine ecosystem to fire decreased the amount of volatile organic compounds and stimulated production of NH+4 and NO3 in the forest floor and that exposure of soil samples to vapors from a terpenoid mixture decreased production of NH+4 and NO3 by mineralization of organic N in these samples. To test the validity of this hypothesis, we studied the effects of different amounts of six terpenoids (α-terpinene, limonene, myrcene, α-pinene, β-pinene, and α-phellandrene) on nitrification in soils incubated at 25 °C after treatment with (NH4)2SO4. The results showed that the terpenoids studied did not significantly affect nitrification in soil even when the amounts applied greatly exceeded the amounts that have been reported to occur in soil. They also indicated that the apparent inhibition of nitrification observed when soils were exposed to terpenoid vapors was due to immobilization of ammonium N by microbial activity stimulated by the organic C in these vapors.

This work was supported in part by the Iowa State Water Resources Res. Inst., and by C.I.L. Inc., Canada. Journal paper no. J-12921 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA. Project 2655.

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