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

Abstract

The decomposition of rice and barley straw saccharides under field conditions was well represented by the first-order kinetics model of Yl = CIe-klr + C2e-kit, where Yr is the remaining amount at time t, kl and k2 are the decomposition rate constants (time-') for the labile fraction (CI) and the non-labile fraction (C2), respectively. About 82% of the total saccharide content of the rice straw was in the labile fraction with a rate constant 0.64-0.8 1, the values for the barley straw being 70-92% and 0.50-0.6 I , 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.

Chemical properties of subsurface peats and their decomposition kinetics under field conditions

“…This had been suggested in another experiment using rice straw in paddy and upland fields, in which the proportions of the labile fraction were 63 and 65%, respectively (Murayama 1984).…”

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

“…In the previous report on the decomposition of straw under field conditions, the decomposition of saccharides was analyzed kinetically (MURAYAMA, 1984). In the present report the changes in the monosaccharide composition will be considered in using the same decomposition data along with some additional experimental results on straw decomposition under field conditions.…”

Relationship between neutral sugars and the degree of humification in Andisols

“…Furthermore cellulose type glucose can be considered to be a sugar of plant origin because its resynthesis.by microorganisms seldom occurs in soils (Murayama 1984a(Murayama , b, 1988. Judging from the low correlation between the amounts of C-GIc and TC, it can be assumed that the accumulation of SOM is not influenced directly by the amount of compounds derived from plant materials.…”

“…According to Cheshire et al (1974), Murayama (1977Murayama ( , 1980Murayama ( , 1984a and Tanaka (1990), the content of mannose was very low in the neutral sugar composition of plant materials such as wheat straw, rice straw, plant residue from paddy soil, and roots of Japanese pampas grass. Therefore mannose can be considered to be a sugar of microbial origin in soil.…”