A glasshouse experiment "was conducted to investigate gypsum application and leaching on the amelioration of" an aluminium (Al) toxic subsoil for wheat growth. Treatments included different rates of gypsum application and amount of leaching prior to wheat being grown. Wheat shoot growth increased when gypsum was applied in both the presence and absence of leaching, but growth was higher with leaching. Gypsum application led to a decrease in toxic Al as a result of a higher ionic strength and activity of AlSO4+ion pairs in the soil solution, and increased Al leached from the soil. Root growth may not be a good bioassay for predicting wheat shoot responses to gypsum applications on acidic subsoils.
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