Differences between natural populations of Trifolium repens L. in response to mineral nutrients. II. Calcium, magnesium and potassium.
T. repens plants from 5 populations from calcareous soils and 5 populations from acid soils were grown in sand cultures with varying levels of Ca, Mg or K. Populations from acid soils, low in Ca, were less responsive to Ca but more responsive to Mg than populations from calcareous soils. Calcareous populations showed yield depression at high K levels (128 ppm.) The response to Ca was correlated with extractable Ca in the native soils. Response to Mg and K was apparently related to cationic ratios in the native soil. Shoot concentrations and uptake of Ca per unit weight of root were higher in populations from acid soils than in populations from calcareous soils. There was no overall difference between population types in concentration and uptake efficiency of Mg or K. Populations from acid soils had higher /Ca + Mg/K + Na and K/Na ratios in the shoot material, but lower Mg/Ca and K/Ca ratios, than did calcareous populations.