Abstract: A green house experiment was conducted to compare the effects of different organic residues on soil microbial biomass C (Cmic) , N (Nmic) and their ratios with total C (Corg) and N (Ntotal) in different soils. Three types of organic residues used were farmyard manure (FYM), town refuse (TR), and sewage sludge (SS), applied separately in sandy, calcareous, and alluvial soils in various concentrations of 10t/fed, 20t/fed, and 30t/fed (1fed=0.42ha). Wheat plants were harvested after 6 weeks and the soils were analyzed for Cmic, Nmic, Corg, Ntotal and pH. The addition of organic residues significantly increased the size of soil microbial biomass. The biomass C and N (Cmic & Nmic) increased consistently with increasing levels of the organic residues in the soil. The FYM was found to be more effective than TR and SS in increasing microbial biomass and this sequence was observed in all the soils used. Similarly, addition of organic residues also caused significant stimulation in Corg and Ntotal in all soils. Also, the ratios of Cmic/Nmic, Cmic/Corg percentage and Nmic/Ntotal percentage were increased with increasing levels of organic residues. The soil pH was decreased significantly with the higher rates of application in all the treatments (FYM, TR, and SS) but remained unaffected at lower rates. The linear regression between different ratios under different levels of organic residues application was also calculated.