Influence of lead, cadmium, and nickel on the growth ofMedicago sativa (L.)

Abstract

Alfalfa (Medicago sativa L.), cv. Iroquois, was grown in the greenhouse in soils amended with additions of either lead, cadmium, or nickel. Metals, at rates varying from 0–250 ppm, were not uniformly mixed but were placed close to the soil surface so as to simulate surface deposition. In one series of experiments the sulphate salt of each metal and two soils were used. In a second series of experiments the nitrate salts and one soil were used. Neither salt of lead significantly depressed alfalfa yields. Both salts of either cadmium or nickel significantly depressed yields. Additions of all metals to the soil resulted in both increased metal uptake and concentrations in alfalfa tissue, particularly for cadmium and nickel. The highest tissue concentrations of cadmium and nickel were associated with plant stunting and necrosis. However, at rates of 125 ppm and less, substantial increases in cadmium and nickel concentrations were obtained frequently without serious yield reductions. Generally, metal concentrations were greatest in the first harvest following metal application. Concentration and uptake of lead and cadmium were greater when the metal was applied to the soil as nitrate than when applied as the sulphate salt.