The comparative rates of phosphate absorption by eight annual pasture species

Abstract

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.