Soil labile carbon (C) and nitrogen (N) are considered to be sensitive indicators of changes in soil C and N pools in response to management practices. A field experiment was conducted to evaluate the effect of corn cob biochar application on C and N management and lability. There were four treatments with four replicates established in a randomized complete block design. Composite soil samples were taken from plots without biochar (CT), from plots incorporated with 15 t biochar ha(-1) (BC-15), and 30 t biochar ha(-1) without or with phosphate fertilizer (BC-30 and BC-30 + P, respectively). The samples were analyzed for basal respiration (BR) and specific microbial respiration rates (qCO(2)), total organic C and labile C pools, and total N and labile N pools. Biochar amendment resulted in a significant increase in the carbon lability index, with the active carbon (AC) recording the highest lability index in the plots treated with 30 t ha(-1) biochar. Among the nitrogen labile pools, the soils amended with biochar at an application rate of 30 t ha(-1) significantly increased the nitrogen lability index only in the active nitrogen (AN). Similarly, carbon and nitrogen pool indices, as well as carbon and nitrogen management indices, were increased in the 30 t biochar ha(-1) treated plots. Among the labile carbon and nitrogen fractions, the AC and AN management indices consistently accounted and predicted the management-induced qualitative and quantitative changes in TC and TN in the tropical soil ecosystem amended with biochar.