Transactions of The Japanese Society of Irrigation, Drainage and Rural Engineering
Online ISSN : 1884-7242
Print ISSN : 1882-2789
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Research Papers
  • Kunio WATANABE, Maki NAKANISHI, Yuki KUSAFUKA, Yoshiko MUTO
    2019 Volume 87 Issue 1 Pages I_1-I_8
    Published: 2019
    Released: January 11, 2019
    JOURNALS RESTRICTED ACCESS

    Nitrification in Andisol containing ammonium sulfate was observed at 22, 24 and 26℃ (batch tests). The decrease in ammonium nitrogen (NH4-N) and increase in nitrate nitrogen (NO3-N) in the batch tests were simulated well by a first-order transformation. The first-order rate constant decreased dramatically with decreasing temperature. Simultaneously, column experiments, in which ammonium sulfate solution was dripped for 9 d and then pure water was dripped for 20 d, were performed at the same temperature for the batch tests. NH4-N remained in the upper soil layer due to adsorption, and NO3-N produced by nitrification leached downward. The NO3-N production decreased as temperature decreased. Then, using Richard's equation and an advection-dispersion model with Gapon convention for cation exchange and first-order transformation for nitrification, the column experiments were calculated with the rate constant obtained by the batch tests. When dissolved and absorbed NH4-N were assumed to have the same rate constant, the calculation overestimated the NO3-N profile in the column experiments. However, the calculation could reproduce the column experiment under the assumption that the absorbed NH4-N had a smaller rate constant than the dissolved NH4-N and started to nitrify when the concentration of the dissolved NH4-N fell below 4 mmol L-1.

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