Dynamics of changes in methanogenesis and associated microflora in a flooded alluvial soil following repeated application of dicyandiamide, a nitrification inhibitor

Influence of repeated application of the nitrification inhibitor dicyandiamide (DCD), on CH4 production and associated microflora in a flooded alluvial soil, was investigated in a laboratory incubation study. Application of DCD at the time of soil incubation resulted in a substantial reduction in CH4 production (31% over that of untreated control). Second repeat application of DCD, on the contrary, annulled the inhibitory effect on CH4 production, restoring it to the level of unamended soil. Application of the third dose of DCD maintained CH4 production almost to the same extent as that of second application. The alleviation of the initial inhibitory effect of DCD on CH4 production was linked to the enhanced degradation of DCD following its repeated application to the flooded soil. Admittedly, abatement of the initial inhibitory effect of DCD on CH4 production in soil repeatedly amended with DCD was also related to the inhibition of CH4-oxidizing bacterial. population and noticeable stimulation of heterotrophic bacterial, population. Results suggest that repeat application of DCD with fertilizer-N to flooded rice soils might not be effective in controlling CH4 production under field condition. (C) 2006 Elsevier GmbH. All rights reserved.