Nickel phytotoxicity in relationship to soil ph manipulation and chelating agents

Abstract

Abstract The main objective of this study was to ascertain effects of some edaphic factors on the uptake and influence of Ni on plant growth sinee Ni is a common trace element contaminant as well as an important component of serpentine soils. Corn (Zea mays L. inbred Ys1/Ys1) was rown in Yolo loam soil amended to give soil pH values of 4.2, 5.6, 7.5, and 8.2. A level of 100 μg Ni/g soil was not toxic to the corn. Shoot concentrations of Ni increased as soil pH decreased for both application rates of Ni. A level of 250 μg Ni/g soil decreased yields more at soil pH below 7 than above 7. Iron, Zn, and Mn levels in shoots did not appear to be directly related to the Ni applications although Fe levels tended to increase as a result of smaller plant size. PI54619–5–1 soybeans (Glycine max L. ) were grown in soil at two different pH values (with and without CaCO3) and with and without a level of 1000 μg Ni/g added as the sulfate and thoroughly mixed with the soil and equilibrated for 1 month prior to transplanting the soybeans with and without application of a chelating agent, DTPA (diethylene triamine pentaacetic acid), commonly used to correct Fe deficiency in plants. Plants were killed in the soil of pH 6.2 when the 1000 μg Ni/g soil was added. The pH 7.2 soil decreased the toxicity of Ni. The DTPA had little effect on yields, but increased the amount of Ni in plants. Nickel decreased the Fe, Zn, Cu, and Mn concentrations of the plants. Stems contained less Ni than did leaves. In another experiment, EDTA (ethylenediamine tetraacetate) greatly increased Ni concentrations in bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) and in barley (Hordeum vulgare L.C.V. Atlas 57) grown in Yolo loam soil, and simultaneously increased Fe concentrations. Lime (CaCO3 or MgCO3) decreased toxicity of Ni in bush beans. DTPA increased Ni transport in bush beans and increased the ratio of Ni in leaves to that in stems at soil pH 7.5 and 8.2, but not at pH 4.0 and 5.8. Key words: Nickelheavy metal toxicitychelating agentssoil pH iron chlorosisspectrographic analysisplant analysis