Several plant species were screened using continuous-flow and spoil culture methods for their p uptake efficiency. In flow cultures, p was maintained at 0.25, 2.5, and 25 umoles; while in spoil cultures p was added at 0, 25, and 75 ug/g spoil to a p-deficient spoil. Alfalfa, Birdsfoot Trefoil, and Emerald Crownvetch showed p deficiency symptoms, while Burning Bush and Russian Thistle showed no such deficiency symptoms; their dry matter yields in the 0.25-Um p treatment was 24% and 36%, respectively, of their maximum yields obtained with 25 um p. The root dry weight ratio in the legumes increased from an average 0.22 to 0.43 with the increase in solution p, while in the weeds the increase was 0.14 to 0.30. The low susceptibility of Russian Thistle to p deficinecy was also demonstrated in the spoil culture experiment. Higher p concentrations were observed in weeds than in legumes or grasses. In general increases in p supply increased p concentrations and decreased zn concentrations. The influence of p fertilization on the tissue concentrations of mn and zn was similar in both flow culture and spoil culture methods.