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Abstract
The use of cow dung as a source of plant nutrients is widespread among many smallholder farmers in Ghana. The benefits of cow dung application in crop production depend on the amount, quality, nutrient-release patterns, and uptake by crops. Samples of cow dung from three main systems of manure management (free range, semi-intensive, and intensive) were collected from the Kumasi Metropolis in the semideciduous forest zone of Ghana and analyzed for nitrogen (N), carbon (C), phosphorus (P), potassium (K), calcium (Ca), magnesium, (Mg), and ash contents. This research was undertaken to corroborate results of an earlier study in the interior savanna zone of Ghana, because manure quality is a function of its management (handling, storage, and transport), animal breed, and vegetation type (feed). Nitrogen content varied from 1.44 to 2.10% with the intensive system of management recording the greatest value. Phosphorus varied from 0.48% under free-range (field) system to 0.80% under the intensive system. The greatest and lowest total K values of 1.74% and 1.11% were respectively recorded under the intensive and free-range management systems. Generally, the study indicated there was relatively better manure quality under the intensive system than in the semi-intensive and free-range (field) systems. The cow dung collected under the various manure-management systems was then incubated in a laboratory study to assess their nutrient-release patterns. The results revealed that the manure under the intensive system mineralized ammonium N during the first 6 weeks of incubation with peak mineralization in the fourth week. Immobilization of nitrate N was observed from the second to the eighth week of incubation from cow dung under all the management systems. Total N [nitrate (NO3−) + ammonium (NH4+)] was immobilized under the free-range and semi-intensive management systems throughout the incubation period except in the first week. Peak net N mineralization was observed during the fourth week of incubation from cow dung under the intensive system of manure management. Results of the study suggested that total mineral N needs of crops might not be met entirely through application of cow dung to Ferric Acrisol due to immobilization during appreciable period of decomposition of the manure.