Effects of Cocoa Pod Husk Ash and NPK Fertilizer on the Yield of Sweetpotato and Distribution of Potassium Forms in an Ultisol of Southeastern Nigeria.

Abstract

The single effects of cocoa pod husk ash (5 tons per hectare), NPK (15-15-15) and their combinations were evaluated on the distribution of potassium forms 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).

 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. Total K, water soluble K, exchangeable K, difficultly exchangeable K and K reserve ranged from 0.07-0.27 cmol/kg with means of 0.54, 0.07, 0.12, 0.13 and 0.22 respectively. Soils treated with 5 tons/ha of cocoa pod husk ash were highest in status when compared to soils treated with soils treated with NPK fertilizer. Cocoa pod husk ash is therefore recommended as a good soil amendment for enhancing soil potassium in southeastern Nigeria Ultisol.

Key words: Cocoa pod husk ash, NPK fertilizer, yield, sweetpotato, potassium forms