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.

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Phosphate flux into roots from soil increased with increase in applied phosphate in eight annual pasture species, except in lupins at higher levels of application, where toxicity was pronounced. The rate of uptake decreased with time, the decrease being least in the clovers. The relationship between rate of uptake and level of applied phosphate was sigmoid for the legumes, less so for erodium and cape-weed, and non-sigmoid for the grasses. Marked differences among species were found in the distribution of absorbed phosphate. It is suggested that the observed differences among species in response to applied phosphate depend on physiological and anatomical characteristics, although the evidence from phosphate fluxes suggest that lupin had an ability to remove phosphate not possessed by other species.

Automated procedures for the determination of ammonium and nitrate in soil extracts are described. Distillation of the extract with magnesium oxide, with subsequent determination of ammonia by the automated indophenol method, is used for ammonium. For ammonium plus nitrate, the nitrate is reduced with titanium( 111) sulphate during distillation with magnesium oxide, and ammonia determined as before. The method has wider application, for example, to the analysis of fertilisers and water samples.

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