2025 Volume 63 Issue 1 Pages 1-10
The purpose of this paper is to determine the conditions that promote denitrification using silicate iron fertilizers, which are conventionally used in paddy fields. Denitrification incubation experiments were conducted in an incubator to evaluate the denitrification gas generation (amount of denitrification) and gas composition (nitrogen and nitrous oxide) in four different soils (Yabe, Koshi, Aso and Matsubase were soil collected in Kumamoto), three different silicate iron fertilizers (Silicate Iron fertilizers with different iron concentrations), different initial soil pH (pH 5, 6, 7, 8, 9). Also, the ratio of denitrification substrate (carbon and nitrogen; C/N 1.2, 1.7, 2.3, 3.5, 5.2, 6.9, 10.4) was to be added. Nitrous oxide was below the detection limit in some of the soils in the treatments with the addition of the Silicate Iron. In soils with relatively low soil C/N, the effect of silicate iron fertilizers was observed and nitrogen gas generation increased. In addition, silicate iron fertilizers were more effective in fertilizers with higher iron and calcium oxide concentrations. As an effect from the soil, nitrogen gas production increased with the addition of silicate iron fertilizers for soil pH in the 5–7 range and low added denitrification substrate (C/N 1.2 to 2.3).
