Effects of organic manure on the quality of coconut soils

Abstract

The performance of goat dung in gravel soil commonly found in coconut lands of the low country wet zone was investigated. Goat dung was applied at the rates of 18 and 24 kg/palm/year and compared with treatments comprising recommended inorganic coconut fertilizer mixture (CU-1) and the control (only dolomite). Dolomite at the rate of 500 g/palm/year was included in all treatments as a basal application. The microbiological (i.e. total bacterial count, total fungal count, biomass C, CO-2 evolution, N mineralization rate, nitrification), chemical (i.e. total N, available P, exchangeable K) and physical (i.e. moisture) changes of soil after the application of various treatments were assessed over a 12 month period. Application of organic manure supplemented with inorganic fertilizers and only inorganic fertilizer mixture, significantly increased (p ltoreq 0.001) microbial counts and microbiologically mediated processes in the soil compared with the control. Addition of goat dung supplemented with inorganics brought about significantly higher (p lt 0.001) microbiological activity in the soil over only inorganic fertilizer treatment. The microbiological parameters showed positive correlation with physical/chemical parameters. Important yield parameters of coconut such as female flowers, number of nuts and copra content per palm per year also showed increases of 49%, 61% and 58%, respectively in treated palms compared with control in the third year after the application of manure/fertilizer. Organic manure treated palms gave a significant increase (p ltoreq 0.05, only in the female flower production.