Effect of Selected Soil Properties on Cadmium Content of Tobacco

In a greenhouse study, limed and unlimed soil from the A horizon of six mineral soils and three organic soils of the southeastern USA was amended with 0, 1, 2, and 4 kg Cd ha⁻¹ as CdCl₂ (1.8, 3.6, and 7.2 mg Cd pot⁻¹). Tobacco (Nicotiana tabacum L.) was grown until flower initiation (42 d). The 2- and 4-kg Cd rates reduced dry weight on the Norfolk soil (Typic Paieudult), but Cd had no effect on dry weight on the other soils. Cadmium concentration was a maximum in the lower leaves and decreased with leaf position up the stalk. At the 2-kg Cd rate, liming reduced leaf Cd concentration in only three soils. Lack of liming effect in the other soils was thought to be a result of high organic matter, high initial pH, or small pH changes effected by the lime. Lime reduced the effects of Cd loading rate and soil types on Cd concentration in tobacco. Stepwise multiple regression was used to relate soil properties to leaf Cd concentration and removal of Cd by tobacco harvest. When organic and mineral soils were considered together, leaf Cd and Cd removal were best related to the Cd sorptive capacity of the soils as determined in previous studies (Cd removed from a Cd solution or sorbed Cd not removed with 1 M KCl). When only the mineral soils were considered, inherent soil properties like sand content, ammonium oxalate-extractable Fe (Feₒ), and pH dominated the regression models. With limed mineral soils (pH 5.7–7.0), models for leaf Cd and Cd removal contained pH, Feₒ, and/or ammonium oxalate-extractable Cd. Model-calculated values and actual values differed by only ±4% so the models should be useful in ranking soils from the southeastern USA for their capacity to retain salt sources of Cd. Soil cation exchange capacity, which is used to regulate Cd loading rates on agricultural soils, did not appear in any of the models. Paper no. 10851 of the Journal Series of the North Carolina Agric. Res. Service, Raleigh, NC. Research supported in part by funds from Fiber Industries, Inc., Charlotte, NC.