AM-241 UPTAKE BY BAHIAGRASS AS INFLUENCED BY SOIL TYPE, LIME, AND ORGANIC-MATTER

Availability of 241Am to bahiagrass (Paspalum notatum), a major forage crop in the southeastern U.S., was studied under greenhouse conditions using 2 soil types, 2 rates of lime, and 4 rates of organic matter. The plants were grown in pots until 3 clippings were obtained. Americium-241 concentrations in plant tissues from the unlimed Dothan (24% clay) soil were, on the average, approximately twice as high as those from unlimed Troup (10% clay) soil. Lime significantly reduced 241Am uptake from both soils. The americium concentration ratios (americium concentration in dry plant tissue/average americium concentration in dry soil) for limed treatments were, in general, one order of magnitude lower than those for unlimed treatments. Organic matter, added to the soils as bermuda grass hay, somewhat reduced 241Am uptake, especially when added at high rates in unlimed soils. The effect of lime on uptake could be attributed to immobilization of americium ions external to the roots as a result of decreased solubility of this radionuclide and/or antagonistic effect of increased calcium ion concentration in the soil solution on americium ions. The effect of organic matter on uptake could be attributed to its fixing capacity for metals.