The effects of a wide range of applied phosphate levels were compared on eight annual pasture species. Marked differences were found between species in response by tops, roots, or whole plant, and in top/root ratio. Different forms of yield response curve were given by the non-legumes, the clovers, and the lupin. At an early growth stage cape-weed, the three clovers, and erodium were highest in phosphorus requirement for near-maximum yield. At the full flowering stage, species ranked in the following decreasing order of requirement: cupped clover > rose clover > subterranean clover > lupin > erodium = cape-weed > Wimmera ryegrass = silver grass. Yields and phosphorus concentrations are compared in relation to applied phosphorus levels. In the early vegetative stage, all species needed at least 0.7% phosphorus in the tops for maximum yield, but by flowering this requirement had fallen to very much lower levels. It is suggested that differences between the species in response to applied phosphate are large enough to influence strongly the botanical composition of pasture and its fertilizer requirements.
Autumn growth and persistence of periodically grazed, spaced plant swards of eleven perennial grasses were measured at two sites registering 750 mm and 1120 mm annual rainfall respectively. The grasses were grown on gravelly podzolic soils of moderate internal drainage and depth of A horizon. After the third summer, autumn regrowth was generally better in Phalaris tuberosa lines than in lines of Dactylis glomerata, Festuca arundinacea and Lolium perenne, Festuca arundinacea cv. Melik and D. glomerata cv. Currie regenerated better than P. tuberosa lines in the first two autumn seasons at the drier site. Capacity for autumn growth appeared to be associated mainly with the level of dormancy achieved by basal buds at mid-summer, though relatively high dormancy of one or two lines at the drier site did not prevent significant plant mortality. Numbers of reproductive tillers per plant in spring and active basal buds per tiller in late summer were less important traits affecting the growth of some lines. We think that rankings for summer dormancy would be useful for screening future introductions for wetter parts (> 750 mm annual rainfall) of the south-western region of Western Australia.
Growth-recording instruments were used to measure extension growth of grass tillers under a variety of outdoor conditions. Variation in the rate of extension growth between tillers was fairly high, but nevertheless was found to be highly correlated with field temperature while only poorly correlated with light energy. By using these instruments, estimates of growth activity can be made rapidly and over relatively short periods of time; and it is suggested that the method may have use in assessing species for sensitivity to temperature.
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