Potential of Chromolaena odorata, Panicum maximum and Pueraria phaseoloides as Nutrient Sources and Organic Matter Amendments for Soil Fertility Maintenance in Ghana

ABSTRACT

The need to maintain soil organic matter in an effort to overcome declining soil fertility on smallholder farms in Ghana cannot be over emphasized. While organic matter such as poultry manure and cow dung are scarce, access to inorganic fertilizers is limited due to high cost. Three high biomass-producing plants (Chromolaena odorata, Panicum maximum and Pueraria phaseoloides), considered as weeds on farmers' fields in Ghana, were evaluated as nutrient sources and organic matter amendments. Mass loss and nutrient release were measured from residues contained in litterbags buried 15 cm below the soil surface. Decomposition and nutrient release constants were estimated by fitting a single exponential model to the data. The initial resource quality analyses showed that the residues contained N and P levels that were higher than the critical values below which net immobilization from the soil would be expected. Decomposition rates of the residues 56 days after burial were not significantly different. All the plant residues had released more than 75% of their constituent elements at the end of the period. The half life of nutrient release of the residues suggest that they can be effectively used together with or without a small amount of mineral fertilizer to produce maize, which is a major cereal in Ghana. Composts prepared from the plant residues were not significantly different in terms of their N, P, K, Ca and Na contents. The pH of all composts was near neutral making them suitable for application to any soil type. The plant residues or compost prepared from them could therefore be used as sources of nutrients and soil organic matter amendment for increased crop production in Ghana.