Manganese Slag Amendment Reduces Greenhouse Gas Emissions from Paddy Soil

Increasing crop productivity and minimizing greenhouse gas emissions from paddy fields are increasingly receiving attention. Slag application not only can maximize the use of solid wastes as beneficial resources for agricultural production, but it also reduces greenhouse gas emissions. In order to determine the most effective slags as soil amendments for greenhouse gas emission reduction, three major slags, i.e., steel, titanium and manganese slags, were applied as soil amendments to paddy soils; correspondingly, the greenhouse gas emissions, cumulative emissions and global warming potential of the soils during one growing season were measured. It was found that applying all these three slags could reduce the methane emission rates and the cumulative methane emissions. Manganese slag significantly decreased methane emissions by 55% compared with the control. Carbon dioxide caused no significant changes among different slag treatments; however, the cumulative carbon dioxide emissions from fields treated with steel and manganese slags were lower than those from control fields. The global warming potential of paddy soil with manganese application was 63% lower than that of the control. Finally, manganese oxide was found to have a negative relation with greenhouse gas emissions. It was inferred that the electron acceptors and the photocatalysis of manganese oxide minerals might have been the main reasons for greenhouse gas reduction. This preliminary result could be further applied to utilizing solid wastes as beneficial resources and to developing carbon fixation and greenhouse gas reduction fertilizers.