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Estimating N mineralization is important both environmentally and economically. Chemical and biological tests have been used for many years in an attempt to predict the N-supplying capacity of soil. Simple methods are needed to predict N mineralization as a means to guide N management in rangeland ecosystems dependent on the natural N-supplying capacity of soils. A short-term C mineralization assay may provide a routine and rapid procedure to attain this goal. The objective of this study was to investigate the association of C and N mineralization in a calcareous soil. A calcareous soil was amended with eight range plant materials and incubated under aerobic condition (50% water holding capacity) at 25°C. The potentially mineralizable C (C 0 ) values ranged from 2232 mg C ⁄ kg soil with a decomposition rate constant (k) of 0.058 ⁄ day for Hordeum bulbosum L. to 2834.2 mg C ⁄ kg soil with a k value of 0.115 ⁄ day for Medicago sativa L. treatment. The k value for Medicago sativa L. treatment (0.115 ⁄ day) was about two times greater than that of Hordeum bulbosum L. (0.058 ⁄ day). The product of k and C 0 (kC 0 ) was highly correlated (r = 0.96, P < 0.001) with N mineralization ⁄ immobilisation (N m ). Moreover, N m was more strongly correlated (r = 0.95, P < 0.001) with cumulative CO 2 -C evolved during the first 6 days of incubation than other incubation periods. Overall, the quantities of N m were closely associated with kC 0 and short-term CO 2 -C evolution. The degree of association between C and N mineralization is time-dependent.