The contribution of organic land use in Korea to the functional diversity of soil microbial communities was determined using Biolog Gram Negative (GN) microplates. This Technique has been broadly used in environmental and ecological microbiology, in which ninety six-well microtiter plates containing various carbon substrates permit these patterns to be determined quickly, economically, and effectively for assessing the soil microbial functional diversity. The fifties organically cultivated fields which differed in the time they enter organic treatment were investigated including its adjacent conventionally managed field and undisturbed native grassland. Principal component analysis of Biolog data revealed large differences in catabolic capability of soil microbial communities between organic land use and undisturbed native grassland. Organic management had little effect on the catabolic capability of soil microbial communities compared to that of conventional management. In addition, no statistically significant difference in functional diversity and substrate evenness was observed by the duration of organic cultivation. Differences were recorded only in relation to the carbohydrates' and carboxylic acid consumptions. In conclusion, the bacterial functional diversity was not differentiated in relation to organic management practices as well as to the duration of organic cultivation. Land use and managements that increased soil organic matter tended to increase catabolic diversity of soil microbial communities.