EFFECT OF FERTILIZER TYPE ON THE LEAF SPOT DISEASE OF SWEET POTATO (Ipomoea batatas (L.) Lam) IN MAKURDI AND OTOBI, BENUE STATE, NIGERIA

Abstract

A multi locational study was conducted at the Teaching and Research Farm of the JS Tarka University Makurdi and the National Root Crops Research Institute Otobi Sub-station, Otukpo Benue State, Nigeria to determine the effect of organo - mineral fertilizers on naturally occurring leaf spot, growth and yield of sweet potato during the 2018 cropping season. The experiment consisted of three rates of mineral fertilizer NPK 15:15:15 applied at 100, 150 and 200 kgha-1 , three rates of organo-mineral fertilizer (Fertiplus® ®) at 1, 2 and 3 tons ha-1 and three rates of poultry manure applied at 5, 10 and 15 tons ha-1 laid out in a randomized complete block design with three replicates and an untreated control. The data collected were subjected to analysis of variance. Results of the study showed that the application of organo-mineral fertilizer had no significant (P ≥ 0.05) effect on the incidence of leaf spot disease of sweet potato at 4 and 6 weeks after planting and leaf spot severity at 10 and 12WAP in both locations. In Makurdi plots treated with Fertiplus® ® 3t/ha and poultry manure at 15t/ha produced significantly greater number of leaves (33.53 and 32.67). The application of poultry manure at 15t/ha recorded the highest yield of 13.39 t/ha and 7.50t/ha at Otobi and Makurdi respectively. Leaf spot incidence was positively correlated with leaf spot severity (0.620**). There was negative significant relationship between leaf spot severity and number of marketable tubers (-0.515**) at Otobi. The use of poultry manure at 15tons/ha and NPK 15:15:15 150kg/ha reduced the leaf spot incidence and severity on sweet potato in the study area.