The influence of lead, cadmium, and nickel on the growth of ryegrass and oats

Abstract

A 24 factorial experiment was conducted under greenhouse conditions. Factors and levels in the experiment were soil pH at 4.5 and 6.4, and cadmium, lead, and nickel added to the soil to provide soil concentrations of 50, 250, and 50 ppm, respectively, above background levels. Two species were grown in succession in the same experimental pots. Ryegrass (Lolium hybridum Hausskn. cv. Tetrelite) was harvested three times and then one crop of oats (Avena sativa L. cv. Garry) was grown and harvested. Plant tissue concentrations of cadmium, lead, and nickel were monitored throughout the experiment. Addition of cadmium to the soil lowered the dry matter yields in all three ryegrass harvests and also reduced the yield of oat grain. The application of lead nitrate to the soil enhanced the yield of ryegrass obtained at the first harvest and also increased the yield of oat grain. Nickel, added to the soil at 50 ppm, was relatively innocuous to ryegrass and oats. The presence of added cadmium, lead, or nickel to the soil resulted in enhanced tissue concentrations of these metals in both ryegrass and oats. This effect was particularly enhanced by a soil pH of 4.5. A single exception to this observation was that lead was not detected, under any of the conditions of this experiment, in oat grain. The presence of lead in the soil enhanced cadmium concentrations in ryegrass tissues. The presence of cadmium in the soil decreased lead tissue concentrations in ryegrass and oat straw. Soil pH interacted with both nickel and lead in the second ryegrass harvest with subsequent changes in tissue cadmium concentrations. At a soil pH of 4.5, the presence of added lead or nickel to the soil significantly increased the ryegrass tissue cadmium concentration beyond that observed at a soil pH of 6.4 with or without enhanced nickel or lead concentrations.