A study was conducted on the effects of different incubation periods (1, 2, 4 and 6 days) on the level of microbial biomass carbon (MBC) in two soil Orders from open-land sites at Putrajaya (Prang Series, Order: Oxisols) and University Agriculture Park (TPU), Puchong, Selangor (Serdang Series, Order: Ultisols). A 100 m² plot was established at each site. About 10 soil samples were collected at the depth of 0-20 cm to form a composite sample. Five replicates were made out of the composite sample for each plot. The physical and chemical properties analyzed in this study include soil texture, bulk density, soil acidity (pH), electrical conductivity (EC) and soil organic carbon (SOC). The fresh soil samples were kept in chiller at 4 °C prior for analysis of microbial biomass carbon (MBC). Both soil series exhibited clay soil texture, where Serdang series had slightly higher amount of sand fraction and lower amount of clay compared to Prang series. Higher moisture and organic carbon also acted as a predisposing factor that causes higher growth of microbial biomass C in Serdang soil. The Serdang series soil samples can be subjected to dichromate digestion after 1^st or 2^nd day of incubation. In contrast, Prang series required a period of 2 to 4 days to achieve ideal amount of microbial biomass C prior for dichromate digestion. Further investigations on wider number of soil series needs to be carried out to obtain a better understanding on microbial biomass C incubation periods. The results obtained will be very beneficial in modifying the chloroform fumigation extraction and incubation timing as it can help in reducing the amount of time.

Keywords: Microbial Biomass C; Incubation Period; Soil Series;