Methane emissions from rice fields amended with biogas slurry and farm yard manure

Abstract

In an experiment on methane-emission measurements from rice fields amended with urea, biogas spent slurry (BSS)+urea, and farm yard manure (FYM)+urea, three distinctive peaks in the methane emissions were observed at 15, 46, and 69 days after transplanting (DAT) due to the availability of readily degradable C-sources. In all cases, the highest peak was at 69 DAT. The steepest Eh drop to a minimum of -320 mV was reached within two weeks of submergence. pH ranged between 7.5 and 8.5. The combined fertilization (FYM+urea) plot showed the maximum emission rate of 4.86 mg m^-2 h^-1 with a total load of 49.44 kg ha^-1 and was 2.3 times higher than (BSS+urea)-treated plot (22.08 kg ha^-1). Grain yields in urea, (BSS+urea) and (FYM+urea) plots were 3.34, 2.94, and 2.85 t ha^-1 respectively, suggesting that biogas slurry is a preferred source over FYM causing lesser environmental pollution without any significant reduction in grain yield.