Effect of Different Storage Methods and Fertilizer Rates on Quality of Sweetpotato (Ipomoea batatas L.) Storage Roots

Storage of fresh roots of two sweetpotato varieties (Apomuden and Okumkom) for up to 12 weeks was conducted from January to March, 2011 (minor cropping season) and from August to October, 2012 (major cropping season) using three storage methods by pit, ash, and grass. Roots were harvested at week 16 after planting. Sweetpotato was previously amended by treatments of chicken manure (CM) and inorganic fertilizer (NPK). The experimental design was randomized complete block. The result shows that Apomuden grown under amended and control plots and stored in grass, ash or pit did not differ significantly from Okumkom grown under the same treatment. Okumkom applied with 15-30-30 kg/ha NPK + 5t/ha CM and stored in grass gave lowest pest infested roots in both seasons. There was a significant difference between Apomuden and Okumkom grown under amended and control plots and stored in ash, grass and pit in weight loss of roots in both seasons. There was no significant difference between Apomuden and Okumkom grown under amended and control plots and stored in pit in root sprout during the major cropping season storage. However, Okumkom and Apomuden stored in pit had higher root sprout compared with ash or grass during the major cropping season. Okumkom applied with 15-15-15 kg/ha NPK +5t/ha CM and 30 – 45 – 45 kg/ha NPK and stored in grass did not sprout at 12 weeks after storage in both seasons. Okumkom applied with 15-30-30 kg/ha NPK + 5t/ha CM and 15-15-15 kg/ha NPK +5t/ha CM and stored in grass produced the least pest infestation, lower root weight and root sprout compared with Apomuden on the same treatment. There was no significant difference between Apomuden and Okumkomgrown under amended and control plots and stored in grass, ash or pit in rotten roots during both storage periods. However, for lower rotten roots, the amended roots should be stored in pit than in grass or ash.