Decomposition kinetics of straw saccharides and synthesis of microbial saccharides under field conditions

SUMMARY The decomposition of rice and barley straw saccharides under field conditions was well represented by the first‐order kinetics model of Y t = C 1 e − k 1 t + C 2 e − k 2 t , where Y t is the remaining amount at time t, k 1 and k 2 are the decomposition rate constants (time −1 ) for the labile fraction ( C 1 ) and the non‐labile fraction ( C 2 ), respectively. About 82% of the total saccharide content of the rice straw was in the labile fraction with a rate constant 0.64–0.81, the values for the barley straw being 70–92% and 0.50–0.61, respectively. The non‐labile fraction appeared to persist for a long time, with a half‐value period of 9–59 months. Barley straw and its saccharides decomposed at a slower rate than rice straw. Much more favourable initial decomposition was observed in a paddy field than in an upland field. Mannose, fucose, rhamnose and ribose were synthesized in parallel with the flush of decomposition of straw saccharides.