Organic and Inorganic Fertilizer Effects on Incidence of Weevil (Cylas spp.), Growth and Yield of Sweet Potato in the Forest, Savannah Transitional Zone of Ghana

Two field experiments were conducted at the Multipurpose Crop Nursery of the University of Education Winneba, Mampong Ashanti campus during from September, 2017 to December, 2018. The study was aimed at determining the organic and inorganic fertilizer effects on the incidence of weevil (Cylas spp.), on the sequential harvesting and vertical distribution of tubers and the, growth and yield of sweet potatoes in the forest-savannah transitional zone of Ghana. Severe weevil infestation was more prevalent on Ogyatanaa than Ogyefo in the minor season; there was a more severe weevil infestation at the second harvest than at the first harvest in the minor season, In the major season there was more severe weevil infestation on tubers at the first harvest than at the second harvest. Ogyatanaa grown at 5 t/ha Chicken Manure produced the highest number of weevil (Cylas spp.), infested tubers at the first harvest. Ogyatanaa grown at 300 kg/ha N.P.K. produced the lowest number of weevils (Cylas spp.), infestations at the first and second harvests. Ogyatanaa grown at 300 kg/ha N.P.K at a depth of 5cm recorded the highest number of (8) weevils infested tubers at the minor season. At a depth of 10 cm, six (6) tubers were found to be infested, while at a depth of 15 cm and 20 cm the number of infested tubers was found to be four (4) and two (2), respectively at the minor and major seasons. Ogyefo grown with 150 kg/ha N.P.K. + and 2.5 t/ha Chicken Manure produced the lowest level of weevil infestation at a depth of 5 cm, only two weevils and at a 10 cm depth, only one weevil was found at the minor and major seasons. At 15cm and 20cm depths no weevils were found. In the minor and major seasons Ogyefo and Ogyatanaa should be grown with 150 kg/ha N.P.K. and 2.5 t/ha Chicken manure and ridging should be done to bury the tubers deep in the soil, to get longer vertical distribution to produce the lowest level of weevil infestation.