Soil pH and exchangeable aluminium in contrasting New Zealand high and hill country soils


  • A.E. Whitley
  • J.L. Moir
  • P.C. Almond
  • D.J. Moot


Soil acidity and associated aluminium (Al) toxicity severely limit the establishment and growth of legumes in New Zealand high country pastures. A survey of 13 soils differing in location, soil order, parent material and climate, showed soil pH to range from 4.9 to 6.4 and exchangeable Al (0.02M CaCl2) concentrations of <0.5 to 23.3 mg/kg. At all sites and at varying soil pH 􀁄􀁑􀁇􀀃 􀁓􀁕􀁒􀂿􀁏􀁈􀀃 􀁇􀁈􀁓􀁗􀁋􀁖􀀏􀀃 􀀤􀁏􀀃 􀁚􀁄􀁖􀀃 􀁓􀁕􀁈􀁖􀁈􀁑􀁗􀀃 􀁄􀁗􀀃 􀁆􀁒􀁑􀁆􀁈􀁑􀁗􀁕􀁄􀁗􀁌􀁒􀁑􀁖􀀃 above the toxicity threshold for sensitive legumes. Brown soils had the overall highest Al concentrations from 0.8 to 23.3 mg/kg, and volcanic soils the lowest from <0.5 to 6.7 mg/kg. The soil and environmental factors other than soil pH that drive variability in soil exchangeable Al require further investigation. Keywords: soil pH, soil exchangeable aluminium, toxicity, soil type






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