EFFECTS OF PH AND PHOSPHATE STATUS OF A SILTY CLAY LOAM ON MANGANESE, ZINC AND COPPER CONCENTRATIONS IN SOIL FRACTIONS AND IN CLOVER

The field pH of a silty clay loam soil affected Mn, Zn and Cu concentrations in the fraction extracted by DTPA [diethylenetriamine pentaacetic acid]; lower pH soils had higher metal concentrations. The soil pH also affected Mn and Zn but not Cu concentrations in the soil solution, and in shoots of clover grown in pots. Metal concentrations in soil fractions were not affected by soil phosphate status, but Zn and Cu concentrations in clover shoots were significantly lower when plants were grown on soils of high phosphate status. Mn and Zn levels in shoots were predicted slightly more accurately by using soil solution data than by using concentrations extracted by DTPA.