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This article in SSSAJ

  1. Vol. 50 No. 3, p. 803-806
    Received: July 3, 1985

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Influence of Thiosulfate on Nitrification of Ammonium in Soil1

  1. H. H. Janzen and
  2. J. R. Bettany2



Ammonium thiosulfate, a common nitrogen (N) and sulfur (S) source in fluid fertilizer formulations, has been reported to inhibit soil nitrification processes. A laboratory study was established to determine the degree and persistence of the inhibitory effect and to examine the agronomic potential of thiosulfate as a nitrification inhibitor. Thiosulfate applied to the soil was rapidly oxidized with a temporary accumulation of tetrathionate. The formation of nitrate (NO-3) from applied ammonium (NH+4) was markedly suppressed at higher rates of applied thiosulfate. At the highest rate of thiosulfate application (100 mg S kg−1), relative inhibition of NO-3 production over 22 d was 55% as compared to 57% for nitrapyrin, applied at 2 mg kg−1. Unlike nitrapyrin, thiosulfate inhibited the second nitrification reaction, the oxidation of nitrite (NO-2) to NO-3, and resulted in the accumulation of NO-2 at concentrations as high as 42 mg N kg−1. This accumulation of NO-2 may represent a serious drawback to the use of ammonium thiosulfate as a nitrification inhibitor under some conditions since NO-2 is known to be toxic at relatively low concentrations.

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