Replacement of cv. Yarloop in swards by new genotypes of Trifolium subterraneum L. subsp. yanninicum and the effects of defoliation

Abstract

Yarloop is a waterlogging-tolerant cultivar of Trifolium subterraneum subsp. yanninicum; it is highly oestrogenic. It is known to be a strong competitor and is widely grown in south-western Australia.

Three new low-oestrogenic, waterlogging-tolerant genotypes of subsp. yanninicum were grown in monoculture, and in binary mixture in competition with cv. Yarloop, in large boxes in a glasshouse. Of the three, Y111 and Y136 gave satisfactory growth relative to Yarloop, and exhibited similar flowering and seed production; cv. Larisa, a late-maturing type, performed well until flowering and had a lower seed number than Yarloop. A second experiment examined the effects of defoliation during the vegetative phase on the relative performance of cv. Yarloop and cv. Larisa growing in mixtures of varying proportions. Two overall densities were used. The dominance of Yarloop over Larisa in uncut swards, due to its more vigorous growth habit, was nullified by regular cutting.

The agronomic implications of the results are discussed.