SUPPRESSION OF METHANE FLUXES FROM FLOODED PADDY SOIL WITH RICE PLANTS BY FOLIAR SPRAY OF NITROGEN FERTILIZERS

A pot experiment was conducted to evaluate the effects of the kind of ammonium fertilizers (ammonium sulfate, ammonium chloride, and urea) and method of topdressing (broadcasting and foliar spray) on the methane fluxes from paddy fields. Among the broadcasted plots, the methane flux from the ammonium sulfate plot to the atmosphere was the lowest, followed by the ammonium chloride and urea plots, in this order. Topdressing by foliar spray reduced the methane fluxes in each fertilizer plot compared with the respective broadcasted plots, with a reduction of 45, 60, and 20% in the ammonium sulfate plot, the ammonium chloride plot, and the urea plot, respectively. Topdressing by foliar spray decreased the grain yield. Among the three kinds of nitrogen fertilizers, the methane flux rate for the production of a unit weight grain was the lowest in the (NH4)2SO4 plot in both methods of topdressing. Topdressing of (NH4)2SO4 fertilizer by broadcasting was the most appropriate method in this experiment, when both the grain yield and methane fluxes were taken into account.