Combine Use of Dry Cocoa Bean Testa Ash and Wood Ash for Soil Fertility Improvement and Maize Yield on Degraded Tropical Humid Alfisol, Southwestern Nigeria

Combine use of dry cocoa bean testa ash (DCBTA) and wood ash (WA) for the improvement of soil fertility and yield of maize (Zea mays, L.) was studied on an Alfisol South Western Nigeria, located at Joseph Ayo Babalola University Ikeji-Arakeji, Ilesa Osun State, Nigeria Teaching and Research Farm from April to July 2017 and from August to November 2017. Four treatments of dry cocoa bean testa ash (DCBTA) at 5 tons/ha, wood ash (WA) at 5 tones/ hectare, dry cocoa bean testa ash (DCBTA) at 2.5 tons/ha, mixed with wood ash (WA) at 2.5 tons/ha and control (C) were used in a Randomized Complete Block Design (RCBD) with three replications. The data collected were subjected to analysis of variance (ANOVA) and the means were compared by the use of Duncan multiple range test (DMRT) at 5% significance level. The study showed that dry cocoa bean testa ash (DCBTA) either used alone or in combination with wood ash (WA) is a valuable fertilizer and can serve as a suitable alternative to inorganic fertilizer in the south western Nigeria especially, DCBTA has higher concentration of potassium (K) and organic carbon than wood ash. Wood ash (WA) 2.5 tones/ha) treatment plus dry cocoa bean testa ash (DCBTA 2.5 tones/ha) produced higher values for plant height, leaf area, chlorophyll, plant diameter, cob length, cob diameter and grain yield against the control that recorded the lowest value. Also, DCBTA improves soil pH as well as increases minerals such as Ca, Mg, Na and in particular, made available phosphorous due to its increment on soil pH. pH increased from 5.4 to 7.4 (DCBTA), 6.9 (WA) and 7.42 (DCBTA + WA). N levels in the soil increased from 0.05% to 2.61% (DCBTA) and 1.95% (DCBTA + WA). Organic carbon (OC) increased from 0.08% to 2.31% (DCBTA) and 3.11% (DCBTA + WA). P level decreased from 3.5 mg/kg to 2.49 mg/kg (DCBTA) and 2.50 mg/kg (DCBTA + WA) which was an indication of P availability to crop during growing season. Maize grain yield increased from 0.74 ton/ha in the control plot to 1.82 tons/ha in DCBTA and 1.89tons/ha in (DCBTA + WA). The study recommends an application rate of 5 tons/ha of dry cocoa testa ash (DCBTA) alone or 2.5 tons/ha combination each of (DCBTA) and WA for maize yield and soil fertility improvement on this type of soil in this agro-ecology.