Denitrification in soil amended with thermophile-fermented compost suppresses nitrate accumulation in plants
2013
Ishikawa, Kazuto | Ōmori, Takashi | Miyamoto, Hirokuni | Ito, Toshiyuki | Kumagai, Yoshifumi | Sonoda, Masatoshi | Matsumoto, Jirou | Miyamoto, Hisashi | Kodama, Hiroaki
NO ₃ ⁻ is a major nitrogen source for plant nutrition, and plant cells store NO ₃ ⁻ in their vacuoles. Here, we report that a unique compost made from marine animal resources by thermophiles represses NO ₃ ⁻ accumulation in plants. A decrease in the leaf NO ₃ ⁻ content occurred in parallel with a decrease in the soil NO ₃ ⁻ level, and the degree of the soil NO ₃ ⁻ decrease was proportional to the compost concentration in the soil. The compost-induced reduction of the soil NO ₃ ⁻ level was blocked by incubation with chloramphenicol, indicating that the soil NO ₃ ⁻ was reduced by chloramphenicol-sensitive microbes. The compost-induced denitrification activity was assessed by the acetylene block method. To eliminate denitrification by the soil bacterial habitants, soil was sterilized with γ irradiation and then compost was amended. After the 24-h incubation, the N₂O level in the compost soil with presence of acetylene was approximately fourfold higher than that in the compost soil with absence of acetylene. These results indicate that the low NO ₃ ⁻ levels that are often found in the leaves of organic vegetables can be explained by compost-mediated denitrification in the soil.
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