Growth, yield and root qualities of two sweet potato (Ipomoea Batatas L.) Varieties as influenced by organic and inorganic fertilizer application

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September, 2015.
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A field experiment was conducted at the Crops Research Institute (CRI) at Fumesua – Kumasi from August to December, 2014. The research aimed at determining the growth, yield and root quality responses of sweet potato (Ipomoea batatas L) to organic manures (poultry manure and cow dung) and inorganic fertilizers (NPK, 15-15-15) and their combinations. The experimental design used for the project was a 2×3 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 NPK, 30-30-30; NPK, 15-15-15 + PM (3t/ha); NPK, 15-15-15 + CD (4t/ha); NPK, 22.5-22.5-22.5 + PM (1.5t/ha); NPK, 22.5-22.5-22.5 + CD (2t/ha); NPK, 7.5-7.5-7.5 + PM (4.5t/ha); NPK, 7.5-7.5-7.5 + CD (6t/ha); and No fertilizer amendment (control). Two sweet potato varieties were used for the experiment. These were “Apomuden” and Santom Pona”. The result indicated that on the average, the organic manure and inorganic fertilizer combinations promoted more growth (215.2cm) than the sole applications and the control (186.7), with the greatest marketable root yield (14.8 t/ha) obtained from 7.5-7.5-7.5 NPK + 4.5 t/ha PM. On root dry matter, NPK 15-15-15 + CD (4t/ha); NPK 15-15-15 + PM (3t/ha); and NPK 7.7-7.5-7.5 + CD (6t/ha) produced the highest responses (32.6%, 31.1%, 30.9%) respectively. NPK 22.5-22.5-22.5 + CD (2t/ha); sole poultry manure (6t/ha); and NPK 15-15-15 + CD (4t/ha) recorded the highest protein content (6.1% each). Integrated application of organic manure and inorganic fertilizers (NPK, 15-15-15) are recommended for improved sweet potato production.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfillment of the requirements for the award of Master of Philosophy In Agronomy (Crop Physiology) Degree, 2015