Improving the sustainability of cocoa farms in Ghana through utilization of native forest trees in agroforestry systems
The study investigatedf armers' ecologicalk nowledgea nd managemenrte lating to cocoa aggroforestins the Atwima district of Ghana,w ith the view to selecting and developing the potential of native forest tree species for use as shade in multi-strata cocoa agroforestry systems. More specifically, the study investigate farmers' knowledge about the ecology and managemenot f multi-stratac ocoas ystems,w ith the view to identifying native forest tree species preferred by farmers as shade for cocoa. Based on this preliminary survey of fanner knowledge and preferences, eight indigenous forest tree speciesw ere selectedf or field screening. Field studies involved: (i) assessmenot f their natural distribution in different landuse systems, to determine natural regeneration potential; (ii) evaluation of their phenological patterns and light regimes under their canopies, with the view to determining their suitability for shade provision; (iii) evaluation of growth performance, when planted as shade on cocoa farms; (iv) determination of potential below-ground complementarity in resource use (particularly water) between planted shade and the cocoa, through evaluation of root competitivity indices for the planted species, as well as determination of water use by means of sap flow measurementT. he study also evaluatedm ethodso f seedp re-treatmentt o enhance germinationo f T. letraptera seedsw, hich usually take a long time to germinate. Farmers' knowledge on site selection for cocoa cultivation was based on soil types and biological indicators. Their description of soil types was based on soil texture and colour. Trees, shrubs, and herbaceous species are used as indicators of soil fertility status. Farmers identified over 50 forest tree species and their role in the cocoa farming system. In Eight of these were selected for screening on-farm and on-station. These included: Albizia adianthifolia, Entandrophragma angolense, Entandrophragma utile, Newbouldia laevis, Pericopsis elata, Terminalia ivorensis and Tetrapleura tetraptera. The natural distribution of these species in mature cocoa farms, fallow lands and natural forest was evaluated and their regeneration potential discussed. Results of phenolog&icIa l patterns and crown characteristicso f the shadet ree speciesa re presenteda nd discussedw ith regards to their temporal complementarity in light (PAR and Red/Far Red light) capture. Seed pre-treatment and vegetative propagation techniques for T. tetraptera were investigated, with results indicating a good potential for the use of locally grown Citrusjambhiri Lush. (rough lemon) juice for seed pre-treatment. Auxin (IBA) application on leafy stem cuttings, at concentrations of 0.2%, 0.4%, 0.8% and 1.6% produced good rooting responses, compared to a control (0%), with 0.4% producing the highest response. Growth performance of all the planted species was evaluated over a two-year period, while root structure of, and rates of water uptake by, E. angolense, T. ivorensis and T tetraptera, which appeared to be the most promising species in terms of initial growth performance on the field, were also investigated. The results showed that T ivorensis, which appeared to be more shallow rooting than the others at this age Q years), was drawing more water from the soil than the other two species while T. tetraptera, with its roots oriented more vertically, was using less water than the others. Above-ground biomass, carbon and nutrient content, as well as litterfall, decomposition and nutrient release patterns of a multi-strata cocoa-Gliricidia agroforest are also reported and discussed.