Yields at an inland and a coastal site planted two years apart, were examined from the start of bunch harvest up till the tenth (inland) or twelfth (coastal) years after planting. Both monthly and annual trends in bunch dry matter production were examined in terms of the development of yield ‘cycles’ and yield levels, respectively. Cycles were most pronounced at the more productive coastal site. There was evidence for external factor(s) modifying timing of yield peaks. Differences in yields between sites involved differences in bunch and female inflorescence numbers; the later due mainly to altered sex ratios.

The yield differences were accompanied by differences in vegetative dry matter production, dry matter partitioning and standing biomass, and involved variation in both radiation interception (via differing leaf area indices) and photosynthetic conversion efficiency. The contribution of genotypic variation to the observed differences was not determined.