Performance of Cassava (Manihot esculenta Crantz) Varieties under Different Soil Amendments

Studies were carried out at Offinso in the Ashanti Region of Ghana to assess root quality of cassava grown with application of poultry manure and NPK 15-15-15 and NPK 23-10-10 fertilizers. The experimental design was a 2 x 6 factorial, arranged in a Randomized Complete Block Design (RCBD) with three replications. The treatments consisted of two cassava varieties in combination with five inorganic and/or organic fertilizer formulations and a control with no fertilizer. The parameters measured were starch content, poundability, nitrogen, phosphorus and potassium contents of cassava roots. The data collected were subjected to analysis of variance using the Genstat Statistical package. The results of the study indicated that Bankyehemaa produced higher starch content (29.86%) than the Nkabom variety. Fertilizer application increased starch content with the combined application of poultry manure and NPK 23-10-10 treatment recording the highest treatment effect (30.40%). Both the organic and inorganic fertilizers applied increased starch content of cassava roots. Poundability was not also affected by both variety and fertilizer application. However, roots treated with NPK 15-15-15 only and poultry manure alone were very poundable (3.0). Variety significantly affected only nitrogen and phosphorus contents of cassava roots. Bankyehemaa had higher content (0.72%) of nitrogen than Nkabom, while Nkabom recorded higher content (1.05%) of phosphorus than Bankyehemaa. Generally, application of fertilizer significantly affected root contents of nitrogen, phosphorus and potassium. However, potassium and phosphorus contents were reduced by the organic fertilizer (poultry manure). The NPK 15-15-15 treatment produced higher potassium (9.37%) and phosphorus (1.36%) contents of roots than the other treatments. The highest nitrogen content of roots (0.78%) was observed in the combined application of poultry manure and NPK 23-10-10 treatment.