Anion-Mediated Salinity Affecting Methane Production in a Flooded Alluvial Soil

In a laboratory incubation study, effects of amendment with sodium salts of SO4 2−, Cl− and HCO3 − either singly or as a mixture on CH4 production in a nonsaline alluvial soil under flooded condition were investigated. Methane production was considerable in the unamended alluvial soil, but was significantly inhibited following amendment with salts of different anions to raise the pore water EC to 8 dS·m−1. SO4 2− was the most inhibitory to CH4 production and the degree of inhibition followed the order SO4 2− > salt mixture > HCO3 − > Cl−. Salt amendment did not adversely affect soil microbial activities as expressed in terms of soil redox potential (Eh) and soil pH. However, readily mineralizable carbon content, an indicator of substrate availability for methanogenic bacteria, differed significantly among the treatments. Most probable number estimates indicated that acetotrophic methanogenic bacterial population was lowest in Cl−-amended soils followed by SO4 2−-amendment with little or no changes in HCO3...