Sweetpotato (Ipomea batatas (L) Lam) is an important food security crop grown in many of the poorest regions of the world mainly by women for food and family cash income (Woolfe, 1992). The plant is traditionally cultivated for food as a root crop (Ruiz, 1981). However, the top is also used as valuable forage for ruminants and other livestock species (Backer et al., 1980; Gonzales et al., 2003; Giang et al., 2004). The tuberous roots and leaves of Sweetpotato are an excellent source of carbohydrate, protein, iron, vitamins A, C, and fibre (Smart and Simmonds, 1995).
The leaves in Liberia, Sierra Leone and some parts of Nigeria have been used as fresh vegetables while the storage roots have also been used as animal feed and also for production of fermentation products (wine, liquor, vinegar) and sugar production (Ellong et al., 2014). The roots may also be baked, fried, canned, used as desserts, pastries, biscuits, flour, pasta, noodles, alcohol (ethanol), sugar or starch.
In Nigeria, fresh sweetpotato is traditionally consumed boiled and eaten with stew, boiled and pounded with either boiled or fermented cassava as ‘fufu’ or boiled and pounded with boiled yam, or boiled with beans and vegetables, fried in vegetable oil or roasted (Mwanga et al.
Processed sweetpotato flour is widely used as thickener and sweetener in the production of kunu, a fermented nonalcoholic drink that is very popular in Nigeria. White-fleshed and yellow to orange-fleshed sweetpotato cultivars are grown. Orange-fleshed sweetpotato has good antioxidant properties because of the high content of carotenoids it contains, over 80 percent of which is beta-carotene.
Once consumed, the beta-carotene in orange-fleshed sweetpotato is converted to vitamin A, an essential nutrient needed in small amounts for growth and normal functioning of the immune, visual and reproductive systems (Slathers et al., 2015).
In spite of its increasing importance as staples food and its potential as a food security, famine reserved and drought tolerant crop, sweetpotato is grown in diverse environments, by small farmers in marginal soils using few inputs (Marique and Hermann, 2010; Amare et al., 2014). This practice has resulted in low yields and a decline in utilization in many countries. Mulindangambo (1987) and Njoku et al. (2001) reported variation in yields due to differences in soil fertility and crop management, while Woolfe (1992) attributed the decline in sweetpotato utilization to pre- and post-harvest losses. High post-harvest losses due to weevil infestation, rotting, thin delicate skin, respiratory losses and sprouting of which up to 60 percent occur at farmers level (Jenkins, 1982). Ray and Ravi (2007) contend that these losses vary between 15 and 65 percent if stored for a period of one to four months.
Like many other crops, sweetpotato responds to high soil nutrient levels, especially nitrogen and potassium (Njoku et al., 2001, Akpaninyang et al., 2015). Most small holder farmers, however, lack the financial resources to purchase inorganic fertilizers to supply these nutrients adequately. There is, therefore a need to look at alternatives of addressing the soil fertility problem. Manures, are a valuable source of crop nutrients and organic matter that can improve soil biophysical conditions making the soil more productive and sustainable for food crop production (Baiyeri and Tenkouano, 2008) Ogoke et al. (2009) noted that even though inorganic fertilizers are quick-acting for soil enhancement to guarantee soil health, they must be used within the contest of integrated soil fertility management relative to soil type and other climatic conditions. Nettles (1960) and Akpaninyang (2015) recommended combined application of organic and inorganic fertilizers to improve the nutrient content of soil and increase the yield and quality of sweetpotato.
In addition to nutrient management, vine cutting and ratooning have been used to increase cumulative vine yield of crops (Ahmed et al., 2012; Inyang, 2016). Understanding the response of sweetpotato to defoliation is crucial to good management. An et al. (2003) showed this practice affects the quality of different vine cuts. Knowledge of the effect of ratooned vines or vine regrowth on sweetpotato yield and quality is rudimentary. Information is also limited on the effect of different storage methods on sweet potato storability and quality. Agronomic research is needed to provide information with a view to improving sweetpotato growth, yield, storability and quality.