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Soil solutions were isolated by centrifugation of moist soil taken from the root-zone of field-grown barley plants and bulk soil from adjacent fallow areas. Low concentrations of Cu, Mn, Zn and Co were found in soil solutions in late winter with increases in spring and early summer. Discrete maxima are generally achieved at some time between May and early July. The precise timing of such maxima appears to depend on the extent of the development of the growing crop and on seasonal influences. The extent to which micronutrient concentrations increase in fallow soils is less than in the root-zone soil solutions although similar trends occur. It is suggested that the increased micronutrient concentrations might result from their mobilization from insoluble forms by biologically produced chelating ligands.

A pot experiment was carried out in order to test the hypothesis that manganese nutrition of wheat was dependent on the phosphorus status of soil as well as on its pH and manganese status. An arable mineral soil whose lime and phosphorus status had been massively adjusted more than 18 years previously was compared with identical soil not so adjusted. Wheat plants were grown to maturity in these soils. Analyses were carried out on both soil and plant samples at intervals. Data for soil pH, soil solution concentrations of manganese and phosphorus, plant dry weight and tissue concentrations of manganese and phosphorus are presented. Concentrations of manganese were depressed in leaf tissue of plants from limed soils and also in high phosphorus soils. The depressed values for limed treatments were explained in terms of depressed soil solution manganese concentrations resulting from elevated pH. The results for high phosphorus soils could not be related to soil solution composition. It was suggested that high soil phosphorus resulted in elevated plant phosphorus which interfered in the uptake and/or translocation of manganese.