Manure nitrogen (N) mineralization is the process that converts organic N to plant available N and is influenced by environmental and soil factors. Field and laboratory incubation studies were conducted to determine the N mineralization and fertilizer equivalence of locally available manures. Available N from solid beef manure amendments (SBM) increased as the studies progressed due to mineralization. Liquid swine manure (LSM) behaved similarly to commercial fertilizer with high initial concentrations of ammonium N which declined continuously as the studies progressed. Manure N mineralization varied significantly (p<0.01) due to the influence soil moisture, manure types and study period as well as their interaction. The fertilizer equivalence of SBM in loamy soil was initially low compared to LSM and finally approached 80 % of ammonium nitrate fertilizer. These studies suggested that manure N mineralization requires emphasis on the initial form of N in manures besides soil moisture, soil temperature, and aeration.