Sprinkler irrigation was tested as a method for the land disposal of leachate wastewater from a municipal sanitary landfill. As part of our objective of determining the efficiency of soils and vegetation as a total system for leachate decontamination, we analysed the concentrations of 18 elements in weeds that volunteered profusely in forage grass plots spray-irrigated for 8 months with 155 cm of leachate. Common ragweed ( Ambrosia artemisiifolia L.) and Pennsylvania smartweed ( Polygonum pennsylvanicum L.) digests analysed by atomic absorption, colorimetry, pyrolysis and auto-titration differed significantly in their accumulation of macro- and micro-nutrients. Smartweed accumulated 0·75% Mn without evidence of phytotoxicity. Calcium content was 1·1% in smartweed and 1·5% in ragweed. Both weed species had higher average micro-nutrient levels than those usually found in forages. Averages for heavy metals were 0·3 ppm Cd, 1·0 ppm Co and Cr; 1·92 ppm Ni, 3·68 ppm Pb and 12·8 ppm Cu. Lime and rock phosphate applied at 11·2 metric tons/ha and superphosphate applied at 0·67 metric tons/ha generally did not affect elemental concentrations of weeds. However, P levels in both species were higher for phosphate treatments and Mn was significantly lower in smartweed from lime and rock phosphate treatments than in unfertilised or superphosphate-treated soils. Results suggested that weeds grown from soils treated with leachate contain Ca, Mg, and Zn in amounts that may be suitable for grazing animals. However, smartweed may have toxic amounts of Mn.