Rapid changes in simple mixtures of Townsville stylo (Stylosanthes humilis) lines differing in flowering time and growth habit

Abstract

The ecological adaptation of Townsville stylo (Stylosanthes humilis) lines was studied by following changes in the composition of mixtures of the lines. At Weipa, a high rainfall site in north Queensland, the composition of a mixture of four maturity types changed rapidly in favour of the later flowering lines, and the earliest line was almost eliminated by the end of the second year. In binary mixtures at 'Lansdown' near Townsville, defoliation every six weeks favoured erect lines but the proportion of prostrate lines was almost doubled at the three week cutting frequency. Changes in mixture composition could not be related to the dry matter yield or pod yield of the monocultures at either site. The capacity of late flowering lines to increase rapidly in populations growing in high rainfall areas, as demonstrated at the Weipa site, could pose problems for the commercial seed production of earlier flowering lines in such areas.