Yield and Storability of Sweetpotato (Ipomoea Batatas (L.) Lam) as Influenced by Chicken Manure and Inorganic Fertilizer

ABSTRACT

Two field experiments were conducted at the Multipurpose Crop Nursery of the University of Education, Winneba, Mampong-Ashanti campus during the minor and major rainy seasons from September, 2011 to January, 2012 and April to August, 2012 respectively to verify the yield and storability of sweetpotato roots as influenced by chicken manure and inorganic fertilzer in the forest transitional agro-ecological zone of Ghana.. In both cropping seasons sweetpotato root tubers were stored for three (3) months after each harvest using three storage methods (Pit, Ash and Grass). The experimental design used for the field experiment was a 2 x 8 factorial arranged in randomized complete block design with four replicates in both studies. In the storability studies the experimental design used was a randomized complete block design with three replications. Sixteen (16) treatments were included in the field experiments. The factors under field study were two varieties of sweetpotato (i) Apomuden (Deep orange-fleshed colour with light orange skin), (ii) Okumkom (White-fleshed colour with light purple skin) and chicken manure and inorganic fertilizer (NPK) combination consisting of seven (7) organic manure and inorganic fertilizer rates and the control. In the storability studies the harvested tubers from the eight field treatments were sorted, cured and stored using the three storage methods (Grass, Ash and Pit). The results obtained revealed that the application of a combination of organic manure (chicken manure) and inorganic fertilizer for soil fertility enhancement in sweetpotato production is a better option than either organic or inorganic fertilizer applied alone. Apomuden grown on 15 – 30 – 30 kg/ha NPK + 5t/ha CM had the highest marketable and total tuber yield during the major cropping season, while Okumkom grown on 15-23-23 kg/ha NPK + 5t/ha CM and other amendments had the highest vegetative biomass (number of leaves per plant and vine fresh weight at harvest) in both seasons. Correlation analyses for both seasons showed that the vegetative growth was negatively correlated with tuber yield and market quality. However, tuber market quality was highly positively correlated with total yield of tuber. The vegetative characters were positively and significantly correlated with each other. The importance of using chicken manure and inorganic fertilizer either alone or preferably in combination as soil amendment to enhance tuber market quality at harvest, tuber nutritional composition with regard to beta-carotene, starch and sugar content over the control was clearly shown from both studies. The sweetpotato root tubers of both varieties with regard to beta- carotene, starch and sugar contents increased with manure application, especially, during the minor season. The

results from both seasons clearly showed that for both varieties the pit method was the most effective storage method in terms of beta- carotene as well as starch and sugar contents over  both ash and grass storage. Pit storage of Apomuden and Okumkom grown on amended and control plots resulted in improved beta-carotene, starch and sugar contents of root tuber and also stored better than ash and grass storage systems in both seasons. With regard to the cost benefit analysis Apomuden and Okumkom grown on 30-30-30 kg/ha NPK treatment dominated the other amended plots and the control in both growing seasons.