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Effects of Organic-based and Foliar Fertilizers on the Growth, Yield, and Quality of Cocoa (Theobroma cacao L.)
Thesis Abstract:
The study aimed to evaluate the effects of different types of fertilizers on cocoa growth production and quality of cocoa beans. Field experiment was undertaken to study the effects of organic-based and foliar fertilizers on soil fertility improvement, growth, yield, and bean quality of cocoa grown on Segamat series soil. Experimental plots were prepared in the Malaysian Cocoa Board (MCB) experimental farm with five treatments and four replications. The number of pods (successful cherelles) was recorded every month, starting two months after treatments. The total number of harvested mature pods was recorded from October 2004 to June 2005. The potential calculated yield was then estimated using the collected data of number of pods (successful cherelles) and harvested pods. Five pods were sampled out from each plot to determine pod and bean quality indicated by dry weight of husk, length and diameter of pods, weight of harvested pods, average number of beans/pods, single dry bean weight, and pod index. Pot experiment was conducted under glasshouse conditions using cocoa seedlings of clone KKM 22 and PBC 130 grown on Segamat series soil with five treatments. The experiment was conducted to determine the effects of organic and foliar fertilizers (as measured by plant height, stem diameter, and weight of root and top) on the growth of cocoa seedlings. The experiment was conducted for 20 weeks starting August 2005 until January 2006. Root-shoot ratio and plant height showed no significant response to treatments except stem diameter, root biomass, and shoot (plant top) dry weight.
Results showed that application of fertilizers gave no significant difference on the growth, yield, or quality of cocoa. Therefore, further soil and leaf analysis had been carried out to identify the actual problem of yield limitation by determining the concentration of macro and micronutrients. It was discovered that manganese (Mn) concentrations in soil and leaf samples for field experiment were threefold higher than the adequate range, possibly resulting in manganese toxicity. Therefore, cocoa was not grown on good soil. Manganese toxicity had been found to be the possible reason of cocoa yield and quality limitation. The Segamat series soil contains minerals such as pyroxene, which contributes to Mn. Initial status of Segamat series soil indicated that Mn concentration was 113-150 mg/kg, which was beyond the adequate range of 20-40 mg/kg. The addition of Mn through fertilizer application has made the problem worst. It was recommended that enough lime should be applied to the soil since the present liming program (500 g/plant or 0.5-1 ton/ha/y, broadcast once a year) has been insufficient to increase soil pH to an adequate range of 5.5-7.0 in order to obtain better yield and quality of cocoa grown on Segamat series soil.