Aluminium toxicity in New Zealand soils: Preliminary results on the development of diagnostic criteria

Abstract
White clover (Trifolium repens) was grown at 6 pH levels and 3 rates of applied P on 2 soils: a steepland yellow-brown earth (yBE), and a brown-granular clay (BGC) , in a glasshouse trial. Aluminium (AI) toxicity limited growth at pH(KCI) 1.0-2.0 me./100 g, 0.02M CaCI,-extractable Al >3.0-5.0 μg/g soil, and soil solution Al activity >9-15μM. Critical values for pH(H.O) and Al in soil solution were dependent on soil type and P treatment.