Combined application of basic slag and methanotroph-formulation have good potential to mitigate greenhouse gases emissions in lowland rice ecology

Abstract

Rice acts as a source of greenhouse gases (GHGs) and contributes about 47 and 58% of the world's agricultural emissions of methane (CH4) and nitrous oxide (N2O), respectively. So, mitigation of CH4 and N2O emissions from rice ecologies is an issue in present day climate change scenarios. Application of value-added soil amendment like basic slag (waste of steel industries) and use of efficient methanotroph formulation is an environmental and eco-friendly option to reduce GHGs emissions. However, those options were less exploited and documented. In our study, we imposed eight treatments viz., (i) control (recommended dose of fertilizer; RDF); (2) basic slag (BS; @ 1 t ha−1); (3) BS + methanotroph (root dip) [BS + MTH(R)]; (4) BS + Methanotroph (acacia-based formulation at 7 DAT) [BS + MTH(F)]; (5) BS + Methanotroph (root dip + acacia-based formulation at 28 DAT) [BS + MTH(R&F)]; (6) Methanotroph (R) [MTH(R)]; (7) methanotroph (F) [MTH(F)]; (8) methanotroph (R&F) [MTH(R&F)]. The CH4 reduction percentage was higher in BS + MTH(R&F) treatments (15.1 and 13.1% in wet and dry season, respectively) than in the control. Similarly, the N2O reduction percentage was also higher in BS + MTH(R&F) treatments (13.9 and 15.2% in wet and dry seasons, respectively) over control. The BS + MTH(R&F) treatment significantly reduced GWP by 14.9% and 14% in the wet and dry seasons, respectively. The average CH4/N2O emissions and GWP had a significant effect on RDF, BS, MTH and BS + MTH, however, no significant difference was observed between MTH and MTH + BS. Thus, the combination of basic slag and methanotrophs could be used simultaneously to reduce the GHGs emissions and climate change mitigation.