An experiment was conducted to study the population dynamics of microbially enriched organic manures and their nutrient composition. Organic manures (FYM, vermicompost and biogas spent slurry) were enriched with the lignite based microbial cultures (Azospirillum sp., Pseudomonas striata and Trichoderma harzianum) @ one kg each per ton. The rock phosphate was added along with the microbial cultures at the rate of 15 kg per ton of manure and moisture was maintained at 50 per cent and incubated for 28 days. The microbial load in the organic manures before and after their enrichment was enumerated. MPN technique was used for the enumeration of free living nitrogen fixers, serial dilution and the standard plate count technique was used for enumeration of P- solubilizing bacteria and Trichoderma sp. The microbial estimation results revealed that the maximum microbial population was attained on 14^th day after enrichment. Among the enriched organic manures, the highest population (free living nitrogen fixers, phosphorus solubilizing bacteria and Trichoderma sp.) was observed in enriched vermicompost (12.24×10³, 92.60× 10⁴ and 14.50 ×10³ cfu/g, respectively) followed by enriched FYM (7.9×10³, 78.17× 10⁴ and 10.17×10³ cfu/g, respectively) and enriched biogas spent slurry (7×10³, 75.17× 10⁴ and 9.67 ×10³ cfu/g, respectively). Among the enriched organic manures, highest N, P and K content (1.70, 1.09 and 1.24%, respectively) was observed in enriched vermicompost followed by enriched FYM (1.40, 0.94 and 0.97%, respectively) and enriched biogas spent slurry (1.38, 0.60 and 0.92%, respectively) as compared to before enrichment of respective organic manure samples.