Behavior of Anaerobic Decomposition Products in Submerged Soils

The effects of soil properties, organic materials applied as amendment, and temperature on the behavior of anaerobic decomposition products of organic matter in submerged soils were studied. Methane and carbon dioxide as final products; acetic, butyric, propionic, isovaleric, p-hydroxybenzoic, vanillic, p-coumaric, ferulic, and sinapic acids, and methanol, ethanol, acetaldehyde as intermediate products were detected during the incubation, and the time course of their formation and decomposition was investigated. Soil amendment with either rice straw or green manure enhanced the formation of carbon dioxide, methane, and acetic acid. Green manure application enhanced the formation of isovaleric acid and alcohols, whereas rice straw application enhanced the formation of phenolic acids. Compost amendment did not enhance the formation of anaerobic decomposition products. Incubation at 20°C inhibited methane formation remarkably, resulting in an increase in the accumulation of volatile fatty acids and alcohols. Incubation at 35°C promoted the formation of carbon dioxide and methane remarkably, accelerated the formation and decomposition of intermediate products, and increased the amount of accumulated acetic acid in non-amended soils and that of acetaldehyde in amended soils. The pH and the content of active iron oxides and easily reducible manganese seemed to affect greatly the time course of anaerobic decomposition of organic matter in soils.