Uptake of Cadmium from Phosphate Fertilizers by Peas, Radishes, and Lettuce
1978
Reuss, J. O. | Dooley, H. L. | Griffis, William
Cadmium uptake from phosphate fertilizers by radish (Raphanus sativus L.), lettuce (Latuca sativa L.), and garden peas (Pisum sativum L.) was investigated in the greenhouse. Fertilizer in all treatments was applied at the rate of 100 µg P/g soil to pots containing 4 kg soil. When reagent grade mono-calcium phosphate was used as a P source on a coarse-textured acid soil, Cd contents of edible radish roots and tops were < 0.4 µg/g dry weight; while the Cd content of lettuce, and pea seeds and foliage was < 0.2 µg/g. The use of concentrated superphosphate (CSP) containing 174 µg Cd/g resulted in plant Cd levels of 2.4, 3.4, 6.3, 0.9, and 0.5 µg/g for radish roots, radish tops, lettuce, pea seeds and pea foliage, respectively. On a medium-textured calcareous soil the use of this CSP increased the Cd content of radish tops from 0.8 to 1.4 µg/g, while in lettuce the increase was from 0.8 to 1.2 µg/g. The effect on radish roots from calcareous soil was nonsignificant. Pea seeds and foliage on this soil were below our Cd detection limit of 0.2 µg/g. Uptake on both soils was a linear function of the Cd content of the fertilizer. With the acid soil, uptake of Cd from CSP was essentially the same when the fertilizer was placed in a spot 5 cm below the seed as when mixed with the soil. Di-ammonium phosphate (DAP) containing 157 µg Cd/g resulted in similar uptake to the CSP when mixed with the soil, but spot placement of DAP almost completely eliminated Cd uptake from the fertilizer. In the calcareous soil spot placement increased Cd uptake from the CSP fertilizer but slightly depressed uptake from DAP.
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