CO2 Flux from a Japanese Tropical Soil Applied with Glucose and Starch.

Decomposition of organic substances in soils can be a significant key to understand the terrestrial carbon dynamics. Carbon dioxide (CO₂) flux behavior from soils with simple mono or polysaccharide addition is not well understood. Therefore, in this study, the effects of mono and polysaccharide addition on carbon flux released from a soil were investigated.

A Japanese tropical soil dried and passed through 2mm sieve, was amended with glucose or starch (¹²C) with application rates of 0.05%, 0.5%, and 5% (w/w) and incubated for 21 days. The CO₂flux rates from the soil were measured using a closed static chamber method of alkali trapping.

The carbon flux from the soil with glucose or starch with all application rates followed well the sigmoid equation. The maximum CO₂fluxes and the mineralized rates of both saccharides were increased with the application rates, except for the mineralized rate of the 5% glucose being lower than that of the 0.5% glucose rate.

Examining the initial slope of the carbon flux rates with time until the time when the rates reached to the half of the maximum flux rates revealed that there were no significant differences on the slopes by the application rates. This could indicate that both glucose and starch were decomposed with similar rates in the soil.

However, it was observed that there was a time lag of CO₂ releasing from the soil with starch being slower than that with glucose. Since starch is composed of two glucose molecules, it may be possible that the starch took more time to be consumed due to the breakdown into the glucose, which may have caused the delay of CO₂ release. Therefore, the carbon dynamics in soils can be influenced by the input rates and/or properties such as molecular structures.