Indigenous microorganisms (IMO) are widely used in agriculture due to their high ability in bio-degradation.
However, their decomposition abilities of different organic materials is still limited. This study aimed to assess
fifteen IMOs’ sourced from different farming systems in Soc Trang province, Vietnam ability to decompose rice
straw, sugarcane bagasse, cocopeat, sawdust, and rice husk. Microbial density capable of decomposing cellulose
was determined by the plate counting method on agar medium containing 1% carboxymethylcellulose. Cellulose
degradation capacity of IMO was estimated by the Congo red method with determination of a halo zone
diameter. Finally, the decomposition capacity of IMO of organic materials was determined by the mass loss
method after 30 days of inoculation under laboratory conditions. The results showed that the microbial density
of cellulose decomposing microbes in IMO was around 10 5 colony-forming units (CFU)/g and all 15 IMOs had
halo zone diameters varying between 3.38-8.63 cm. Results of the laboratory decomposition experiment for five
different organic materials revealed that decomposition of rice straw ranged between 52.2-57.9%, and
decomposition of sugarcane bagasse changed from 19.03 to 47.72% while the values for the control treatments
without IMO inoculation of these two materials were 20.39% and 11.81%, respectively. However, for other
materials including coco peat, sawdust and rice husk, all fifteen IMOs exhibited very low capacity in
decomposition and there was no significant difference between the treatments with and without IMO
inoculation. The results of this study indicated that IMOs can be used to increase decomposition of some
agricultural waste products, but varies depending on organic matter.