EFFECTS OF COCOA POD HUSK ASH AND NPK FERTILIZER ON SOIL NUTRIENT STATUS AND SWEETPOTATO YIELD IN AN ULTISOL IN SOUTHEASTERN NIGERIA

The single effects of cocoa pod husk ash (CPHA) - 5 tons per hectare, NPK (15-15-15) and their combinations were evaluated on soil chemical properties and yield of sweetpotato (Ipomoea batatas L. (Lam) in an Ultisol in Southeastern Nigeria. The treatments were: 5 tons/ha of Cocoa pod husk ash (A), 200 kg/ha of NPK Fertilizer + 5 tons/ha of Cocoa pod husk ash (B), 300 kg/ha of NPK Fertilizer + 5 tons/ha of Cocoa pod husk ash (C) 200 kg/ha of NPK Fertilizer (D), 300 kg/ha of NPK Fertilizer (E) and No treatment –Control (F). All the applied treatments increased soil pH except the sole application of 200 kg/ha NPK fertilizer, which reduced the soil pH than what it was before treatment application. Other soil nutrients such as % organic carbon, % total nitrogen and exchangeable potassium were increased when 5 tons CPHA was combined with 200 kg/ha NPK fertilizer. While 300 kg/ha NPK applied singly significantly increased soil Available P after harvest. Saleable tubers of sweetpotato were significantly (P<0.05) higher in plots treated with 200 kg of NPK fertilizer combined with 5 tons/ha CPHA, followed by treatment with 300 kg/ha of fertilizer combined with 5 tons/ha of CPHA. 200 kg of NPK fertilizer combined with 5 tons/ha CPHA is therefore recommended.