Enhanced root yield and β-carotene content of orange fleshed sweetpotato using integrated nutrient management
This study was conducted in 2014 and 2015planting season at the Research farm of National Root Crops Research Institute Umudike, southeastern, Nigeria to determine the effect of integrated nutrient management on root yield and total carotenoid content of orange fleshed sweetpotato. The experiment was a 5x4 factorial laid out in randomized complete block design (RCBD). The treatment comprises of five levels of composite manure (Pig manure, cowdung and poultry manure) applied at the rate of 0, 2, 4, 6 and 8t/ha and mineral fertilizer (NPK 15:15:15) applied at the rate of 0, 200, 400 and 600kg/ha. Combined application of mineral fertilizer and composite manure significantly (p<0.05) increased the total and marketable root yield of orange fleshed sweetpotato. Application of 4t/ha composite manure + 400kg/ha NPK gave the highest mean root yield of 15.90t/ha relative to control. The β-content increased generally with increasing rate of the treatment combinations with application of 8t/ha composite manure + 200kg/ha NPK giving the highest β-carotenoid content of 733.2μg/g. Results of the regression analysis showed that Organic matter, total nitrogen, available phosphorous, effective cation exchange capacity and percentage base saturation are the major soil chemical properties that contributes to increase in the β-carotene content of the orange fleshed sweetpotato. From the results obtained, application of 4t/ha composite manure + 400kg/ha NPK is recommended for good root yield while application of 8t/ha composite manure + 200kg NPK is recommended for farmers who wish to improve the carotenoid content of orange fleshed sweetpotato.
Keywords: Composite manure, mineral fertilizer, root yield, orange fleshed sweetpotato and carotenoid