The performance and profitability of sweet potato (Ipomoea batatas L.) as influenced by propagule length and application rates of cattle dung in humid ultisols

This study was conducted in 2013 and 2014 at the Teaching and Research Farm of the Faculty of Agriculture, University of Benin, Benin City, Nigeria. The aim of the study was to evaluate the effect of propagule length and cattle dung application rates on the growth, yield and profitability of sweet potato (Ipomea batatas L.) in a humid Ultisols. Treatments consisted of three different propagule lengths of vine cuttings (30, 40 and 50 cm) and three rates (0, 225 and 450 kg N ha−1 ) of cattle dung in a 3 × 3 factorial arrangement fitted into randomized complete block design and replicated three times. The productivity of sweet potato was enhanced by the application of cattle dung and increasing propagule length positively. Growth and yield variables varied significantly with propagule length and cattle dung application. Number of vines, vine girth and number of leaves increased significantly with increase in propagule length. Cattle dung application rates of 225 and 450 kg N ha−1 had statistically at par number of vines, vine girth, vine length, number of nodes and leaves and leaf area index but significantly higher than unfertilized plants. The highest tuber yield of 26.10 and 22.00 t ha−1 was obtained from vine cutting of 40 cm and 20 t ha−1 cattle manure, respectively. The interaction of propagule length and cattle dung application rate on all growth and yield parameters were not significant. Tuber size significantly (P ≤ 0.05) correlated positively with number of leaves (r = 0.351), number of nodes (r = 0.288), number of tubers (r = 0.377), tuber length (r = 0.475). Tuber yield significantly correlated positively with the number of leaves (r = 0.335), number of tubers (r = 0.281), tuber length (r = 0.365) and tuber size (r = 0.652). The appropriate propagule length and cattle dung application rates were 40 cm and 225 kg N ha−1, respectively as they had the highest return per naira invested. Key words: economic analysis, growth variables, organic fertilizer, tuber yiel