An experiment was carried out to ascertain the status of organic phosphorus (P) and its contribution to P source for plants under monoculture (maize) and crop rotation (groundnut and maize) systems. The amount of organic P in both cropping systems was in the range of 40—50% of total P in P fertilized soils and 70-80% of total P in non P fertilized soils. Mineralization at a rate 0.2 to 16% of the amount of organic P in the soil in a cropping season was detected and this can contribute to 1 to 60 kg P ha-1 for the plants. The C:P ratio in both systems was in the range of 140-160:1 which encouraged mineralization.