Analysis of Nitrification in Agricultural Soil and Improvement of Nitrogen Circulation with Autotrophic Ammonia-Oxidizing Bacteria
2013
Matsuno, Toshihide | Horii, Sachie | Sato, Takanobu | Matsumiya, Yoshiki | Kubo, Motoki
Accumulations of inorganic nitrogen (NH₄ ⁺, NO₂ ⁻, and NO₃ ⁻) were analyzed to evaluate the nitrogen circulation activity in 76 agricultural soils. Accumulation of NH₄ ⁺ was observed, and the reaction of NH₄ ⁺ → NO₂ ⁻ appeared to be slower than that of NO₂ ⁻ → NO₃ ⁻ in agricultural soil. Two autotrophic and five heterotrophic ammonia-oxidizing bacteria (AOB) were isolated and identified from the soils, and the ammonia-oxidizing activities of the autotrophic AOB were 1.0 × 10³–1.0 × 10⁶ times higher than those of heterotrophic AOB. The relationship between AOB number, soil bacterial number, and ammonia-oxidizing activity was investigated with 30 agricultural soils. The ratio of autotrophic AOB number was 0.00032–0.26 % of the total soil bacterial number. The soil samples rich in autotrophic AOB (>1.0 × 10⁴ cells/g soil) had a high nitrogen circulation activity, and additionally, the nitrogen circulation in the agricultural soil was improved by controlling the autotrophic AOBs.
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