Growth and Yield Characteristics of Two Sweet Potato (Ipomoea batatas L.) Varieties as Influenced by Organic and Inorganic Fertilizer Application

A field experiment was conducted at the Crops Research Institute (CRI) at Fumesua – Kumasi from August to December, 2017. The research was to investigate the growth and yield characteristics of sweet potato (Ipomoea batatas L) to the application of organic manure (poultry manure and cow dung) and inorganic fertilizer (NPK, 15-15-15, 300kg/ha) and their combinations. The experiment was a 2x3 factorial with treatments arranged in randomized complete block design (RCBD) with three replicates. The treatments were: sole poultry manure (6t/ha); sole cow dung (8t/ha); sole NPK45-45-45kg/ha; NPK, 22.5-22.5-22.5kg/ha + Poultry manure (PM) (3t/ha); NPK, 22.5-22.5-22.5kg/ha + Cow dung(CD) (4t/ha); NPK, 33.75-33.75-33.75kg/ha + PM (1.5t/ha); NPK, 33.75-33.75-33.75kg/ha + CD (2t/ha); NPK, 7.5-7.5-7.5kg/ha +PM (4.5t/ha); NPK, 7.5-7.5-7.5kg/ha + CD (6t/ha); and no fertilizer amendment (control). Two sweet potato varieties, ‘Apomuden’ and ‘Santom Pona’ were used. The results indicated that on the average, the organic manure and the inorganic fertilizer combinations promoted greater growth than the sole applications and the control. The greatest marketable root yield (14.8 t/ha) obtained from 7.5-7.5-7.5 NPK + 4.5 t/ha PM. For root dry matter, NPK 22.5-22.5-22.5 + CD (4t/ha); NPK 22.5-22.5-22.5 + PM (3t/ha); and NPK 7.5-7.5-7.5 + CD (6t/ha) produced the greatest responses (32.6%, 31.1%, and 30.9%) respectively. Integrated application of organic manure and inorganic fertilizers is thus recommended for improved sweet potato production.