Changes in the monosaccharide composition during the decomposition of straws under field conditions

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Abstract
Changes in the monosaccharide composition during the decomposition of rice and barley straws under field conditions were examined. The proportion of mannose, galactose, fucose, rhamnose, and ribose increased consistently with time, whereas the proportion of cellulosic glucose became smaller consistently. Changes in the proportion of hemicellulosic glucose, arabinose, and xylose followed a somewhat zigzag course, though a consistent increase in the proportion of hemicellulosic glucose was observed after the flush of decomposition. The molar ratio of xylose to mannose decreased sharply at the flush of decomposition, then gradually afterwards, and reflected well the decomposition of the straw saccharides. The ratio of hemicellulosic glucose to cellulosic glucose became consistently larger with time after the flush of decomposition. Samples which contained less straw saccharides with the progression of the decomposition appeared to have larger molar ratios of hexoses to pentoses, deoxyhexoses to pentoses, and hemicellulosic saccharides to cellulosic saccharides. Even after 3 years of incubation, the monosaccharide composition of the straw, though more similar, was still quite different from that of soil, reflecting the persistence of the remaining straw saccharides.