Banana (Musa AAA; Cavendish sub-group) cultivar/density trials in three bioclimatic groups on the north coast of KwaZulu-Natal.
The North Coast of KwaZulu-Natal is a relatively new banana production area, for which there is an absence of local norms, specifically for choice of cultivar and population density. Three cooperative split-plot banana cultivar/density trials were established in December 1991, January 1992 and February 1992 on farms at Eshowe, Nkwaleni and Mposa, respectively. These sites represent Phillips' (1973) Bioclimatic Groups 2,10 and 1 respectively, and have widely divergent climatic potential, ranging from cool, to warm, to hot subtropical. Each randomised trial block, 0.92 ha in extent, comprised five replications of five cultivar main plots, each of which was split into three density sub-plots. The five cultivars planted represent those registered at the time of planting, viz. 'Dwarf Cavendish', 'Williams', 'Grand Nain', 'Valery' and 'Chinese Cavendish'. Sub-plots were planted at 1 666, 2 105 and 2 500 plants ha(-1) and tissue culture plants were used to establish all three trials. The field trials were evaluated over three full cropping cycles and culminated in October 1996. Morphological differences such as pseudostem height and circumference, leaf length and width, number of functional leaves at flowering and harvest, as well as phenological differences such as monthly leaf emergence rates, emergence-to-harvest intervals and harvest cycles, were evaluated. The yield component data comprised measurements of bunch mass, number of hands per bunch and number, length and mass of fingers on the third hand. Productivity was expressed as tonnes per hectare per annum (t ha(-1) an(-1). Each cultivar and density treatment was evaluated independently. However, it was the evaluation of the cultivar/density interaction which formed the basis of the recommendations for the three different Bioclimatic Groups. At the relatively cool Eshowe site, 'Williams' proved to be the most productive cultivar (471 ha(-1) an(-1) over all densities. The highest production (49.8 t ha(-1) an(-1) was achieved from a density of 2 500 plants ha(-1), but due to lower costs per hectare, the intermediate density of 2 105 plants ha(-1) generated the highest gross margin. When the cultivar/density interaction was evaluated, the combination producing the highest gross margin was 'Williams' at 2 105 plants ha(-1). This substantiated the independent evaluations and is consequently the recommended combination for Bioclimatic Group 2. However, the faster cycling of 'Chinese Cavendish' could conceivably result in this cultivar outperforming 'Williams' in future ratoons. At the warmer Nkwaleni site, 'Grand Nain' (57.8 t ha(-1) an(-1) proved to be the most productive cultivar. The density of 2 500 plants ha(-1) was the most productive (64 t ha(-1) an(-1) and also generated the highest gross margin. However, the cultivar/density interaction indicated that 'Williams' at 2 500 plants ha(-1), was the highest producing combination yielding the highest gross margin, and is consequently the recommended combination for Bioclimatic Group 10. At the hot Mposa site, 'Chinese Cavendish' (54.21 ha(-1) an(-1) proved to be the most productive cultivar. The density of 2 500 plants ha(-1) outproduced (57.4 t ha(-1) an(-1) the lower densities and also generated the highest economic returns. However, when the cultivar/density interaction was evaluated, 'Chinese Cavendish' at the lower density of 2 105 plants ha(-1) realised the highest gross margin and is consequently the recommended combination for Bioclimatic Group 1.