Animal manure is used in smallholder farms to improve soil fertility but the quality is often poor. The quality of the manure in the inherent nutrient levels is low and mostly associated with diets fed to the animals and the management of the manure. A study was carried out to investigate carbon and nitrogen (N) mineralisation of cattle manure processed under different management systems. Manure was produced in smallholder farms and in a research station. A detailed laboratory analysis was done to characterise the manure. The manure was subsequently incubated with a humic Nitisol, the dominant soil group in central highlands of Kenya. In the incubation study, data were collected on carbon dioxide evolution and nitrogen mineralisation (NO-3and NH4+). An on-farm trial was conducted to test the effect of two types of manure with different N release rates on maize yield. The on-station manure and manure from farmers' fields showed a net nitrogen release up to 12 weeks of incubation. Some manure from farms immobilised N for most of the incubation period. Carbon dioxide evolution at weeks two and four indicated that there was microbial activity in most of the manure. The release of N in the incubated manure was confirmed in the field study where the on-station manure showed a yield response in maize during the first season. This study shows that manure management affects the rate of N release can affect crop growth in the field. Level of soluble carbon correlated most with N mineralisation.