Growth, Yield and Nutritional Quality of Sweet potato (Ipomoea batatas (L.) Lam) Varieties as Influenced by Fertilizer type and Rates. A Review

Sweet potato (Ipomoea batatas (L.) Lam) is one of the economically important and food securing root crop in Ethiopia.  Fertilizer has greater effect on the yield of sweet potato crop. Growth parameters are the main important yield determining factors in sweet potato and they are highly influenced by soil fertility and soil amendments. Nitrogen, phosphorus and potassium influence growth and reproductive phase of plant growth. Nitrogen supply has a great influence on the production and distribution of dry matter within the plant, particularly affecting root growth relative to top growth at optimum level.

Optimum application of N and P promotes higher photosynthetic activity and vigorous vegetative growth and promotes the chance for emergence of new vines. Applications of N and P influenced days to maturity. Applications of N and P increase shoot dry weight, tuber dry matter content, tuber number, tuber length, marketable storage root yield and total storage root yield. The   total tuber yield of sweet potato increased significantly with up to 1.5 kg ha^-1 to 2 kg ha ^-1 of boron applications.

Orange flesh sweet potatoes (OFSP) were used in food based intervention and also varieties have a potential contribution to alleviate vitamin A and mineral deficiencies. The β-carotene contents were varying within variety and fertilizer level. Application of phosphorus increase the carotene content of tuberous roots of sweet potato in higher yield and affects the unit weight of root tubers. Increasing the supply of nitrogen fertilizer significantly increases β-carotene content. Increase in carotene content with potassium application, as well as with zinc application. Both Sulfur and Nitrogen involve in protein synthesis, intimately linked and are often assumed to be co-limiting. It has been recognized that for every 15 parts of Nitrogen in protein, there is approximately 1 part of Sulfur (15:1 ratio of N: S). Some of application of Sulfur caused formation of more protein that has a nutritional advantage.