Sweet Potato (Ipomoea batatas) Yield Parameters, Soil Chemical Properties and Cost Benefit Ratios Following Incorporation of Poultry Manure and Inorganic NPK Fertilizers in Low Nutrient Ghanaian Soils

The impact of sole poultry manure (6t PM ha-1), sole NPK (200kg NPK ha-1) and their combinations (3t PM + 100kg NPK ha-1 and 1.5t PM + 150kg NPK ha-1) on sweet potato yield parameters and soil nutrients was assessed at Adiembra and Fiaso in Ghana between June, 2011 to November, 2011 using RCBD. Nutritional levels of the sweet potato tubers and the amended soils were analysed with standard laboratory procedures. The 3t PM + 100kg NPK ha-1 produced significantly (P=0.05) the highest tuber yield (tonnes ha-1), tuber length and diameter, and also had the highest percentage of marketable tubers. The total percentage soil nitrogen, organic matter, Total Base Saturation (TEB) and Effective Cation Exchange Capacity (ECEC) were significantly (P=0.05) highest in the 6t PM ha-1 treatment. The 6t PM ha-1 treatment had the highest tuber nutrient values for Ca, Mg, P, S and N. The 3t PM + 100kg NPK ha-1 had the highest cost benefit ratios of 1:4.38 and 1:8.15 at Adiembra and Fiaso respectively. The results demonstrated that combined application of PM and NPK increased sweet potato tuber yield and soil nutrient levels in a cost effective manner.