Fertilizer Treatment Effects on Yield and Quality Parameters of Sweet potato (Ipomoea batatas)

Currently the world is moving towards organic production of crops for the discovered and envisaged advantages. Despite this, farmers are faced with the challenges of the bulkiness of organic fertilizer to be used and further gains that could be accrued from it even if sacrifice of using it is made. To be quite sure of the appropriate fertilizer type to be used in improving quality as well as the tuber yield of sweet potato, this work, therefore, evaluated the effectiveness of organic, inorganic and organo-mineral fertilizers on quality determinants of sweet potato as well as its tuber yield. This experiment was carried out at the Teaching and Research Farm, University of Ibadan. The treatments applied were Pacesetter organic fertilizer at the rate of 3t/ha, inorganic fertilizer (NPK 15:15:15) at the rate 130kg/ha while organomineral fertilizer (comprising NPK 15:15:15 and Pacesetter organic fertilizer) was at the rate of 1.5t/ha and the control .The experiment was laid out in randomized complete block design (RCBD) with tree replications and the fertilizer treatments were applied at four weeks after planting. At maturity, destructive sampling was embarked upon and the sampled plants were partitioned into leaves and tubers. The fresh and dry weights of the samples were taken after which their proximate analyses were done to determine the levels of the quality determinants (moisture content, crude protein, crude fat, crude fibre, Vitamin A and ash content) in them. Final harvesting was done at the end of the experiment to determine the yield per treatments. The data collected were analysed using analysis of variance (ANOVA) with the aid GENSTAT 5 package and significant means were separated using Least Significant Difference (LSD) at 5% probability level. The results indicated that all the above mentioned quality determinants of sweet potato leaves and tubers were not significantly increased by the fertilizer treatments used except for ether extract in the tubers which was significantly improved by organic fertilizer. Also, leaf and tuber dry matter production were not significantly increased by the applied treatments. However, inorganic as well as organic fertilizers significantly increased the final fresh tuber yield of the crop. It was also found that leaves of sweet potato had higher levels of quality indicators than the tubers except for energy content which was higher in the tubers. It is, therefore, recommended that organic fertilizer and, to a lesser extent, inorganic fertilizer (NPK 15: 15:15) be relied upon to increase tuber yield of the crop. Finally, sweet potato should be produced with organic fertilizer since it is more advantageous and the inorganic fertilizer did not produce much higher than it did.