The effects of silicon fertilizer on denitrification potential and associated genes abundance in paddy soil

This study evaluated the effect of silicate fertilizer on denitrification and associated gene abundance in a paddy soil. A consecutive trial from 2013 to 2015 was conducted including the following treatments: control (CK), mineral fertilizer (NPK), NPK plus sodium metasilicate (NPK + MSF), and NPK plus slag-based silicate fertilizer (NPK + SSF). Real-time quantitative PCR (qPCR) was used to analyze the abundances of nirS, nirK, and nosZ genes. Potential N2O emissions and ammonium and nitrate concentrations were related to the nirS and nirK gene abundance. Compared with the NPK treatments, the addition of a Si fertilizer decreased N2O emission rates and denitrification potential by 32.4-66.6 and 22.0-59.2%, respectively, which were probably related to increased rice productivity, soil Fe availability, and soil N depletion. The abundances of nirS and nirK genes were decreased by 17.7-35.8% and 21.1-43.5% with addition of silicate fertilizers, respectively. Rates of total N2O and N2O from denitrification (DeN(2)O) emission were positively correlated with the nirS and nirK gene abundance. Nitrate, exchangeable NH4 (+), and Fe concentrations were the main factors regulating the nirS and nirK gene abundance. Silicate fertilization during rice growth may serve as an effective approach to decreasing N2O emissions.