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Acidic nickel (Ni)-contaminated soils in the vicinity of a Ni refinery at Port Colborne (Ontario, Canada) cause Ni phytotoxicity and require remediation. Thus, a greenhouse test with 11 plant species with a wide range of susceptibility to Ni toxicity was conducted to determine if Ni phytotoxicity of all species could be ameliorated by a high rate of limestone. At the original pH of 5.2, the Welland soil (Typic Epiaquoll; 2900 mg kg-1 Ni) was severely phytotoxic to all plant species tested. Toxicity symptoms in dicots included interveinal chlorosis and necrosis of leaves. In grasses, a banded chlorosis was present. Two limestone rates, 2.5 and 50 Mgha-1, were included in the test. Both liming and plant species significantly affected soil pH, and 0.01 M Sr(NO3)2-extractable soil Ni. Increase in pH exponentially decreased Sr(NO3)2-extractable soil Ni. Grass species were more resistant to Ni toxicity than dicots. Liming soil to pH of 5.9-6.3 enabled good growth of several grass species, but dicot species were still stunted or died. Making the soil calcareous (pH 7.7-7.8) ameliorated Ni toxicity of this highly contaminated soil for all species tested. Concentration of Ni in shoots associated with 25% yield reduction varied among species ranging from 9 to 122 mg kg-1 dry shoots. [ABSTRACT FROM AUTHOR]