Establishment of buffel grass, green panic and Siratro from seed broadcast into a speargrass pasture in Southern Queensland

Abstract

The establishment and survival of seedlings from pasture seed oversown into a native speargrass (Hetevopogon contortus) pasture were studied in southern Queensland. Lime pelleted and unpelleted seed of buffel grass (Cenchrus ciliaris), green panic (Panicum maximum var, trichoglume) and Siratro (Macroptilium atvopuvpureum) were either sown into a cultivated seedbed or broadcast into native pasture pretreated as follows: untreated control; mown to 3 cm; or killed with herbicide. Buffel grass was sown both as fascicles and as caryopses. Establishment was similar in all oversown seedbeds with seedling numbers accounting for 37 % of the germinable seed sown, compared to 49% in the cultivated seedbed. Pelleting increased establishment where competition was present, the effect being greatest for Siratro and least for buffel grass fascicles. Establishment of buffel grass caryopses was markedly inferior to that of fascicles. Seedling survival rather than seed germination was the main factor influencing the success of the pasture sowing. Less than 1 % of the grass seedlings survived in the mown and control plots, but 38 % survived where competition was controlled by herbicides. Siratro survived equally as well as the grasses in the herbicide-treated plots, but survived markedly better when in competition with native grasses. Surface broadcasting into native pasture is therefore considered a satisfactory, though risky method of establishment for legumes such as Siratro, but not for grasses, unless competition is controlled.