A study of the phosphorus responses of a wide range of accessions from the genus Stylosanthes

Abstract

The effects of a wide range of phosphorus levels on the growth and uptake of phosphorus by 30 accessions of the legume genus Stylosanthes, representing seven species, were compared in a glasshouse experiment. The basic data from the experiment were subjected to a numerical classification, and accessions with similar patterns of response were grouped to simplify description and interpretation of the results.

Differences in growth and phosphorus uptake under conditions of severe deficiency were fairly small, but there were appreciable differences between groups in the dry matter produced per unit phosphorus absorbed. With progressive improvement in the supply of phosphorus, large differences developed between the groups in growth and phosphorus uptake. One group, in which nodulation was partially or completely ineffective, responded poorly in growth and phosphorus uptake to additions of phosphorus. Other groups, however, were effectively nodulated, and appeared to differ considerably in their inherent growth rates and hence in their uptake of phosphorus during the 55 days of the experiment.

At moderately high levels of applied phosphorus (equivalent to between 96 and 192 kg P/ha) accessions in several groups developed foliar symptoms resembling 'phosphorus toxicity', had depressed yields of dry matter, and accumulated phosphorus in their tops to high concentrations.