SCREENING SPECIES AND CULTIVARS FOR THEIR TOLERANCE TO ACIDIC SOIL-CONDITIONS

The major phytotoxins in acid soils are aluminium and manganese. Toler ances to Al and to excessive Mn are independently inherited and Al and Mn solubilities in soils vary. In this work, the response of pasture grasses and legumes to soil acidity was studied on three soils with di fferent Al and Mn concentrations. One provides moderate concentrations of Al with little Mn; one provides high concentrations of both Al and Mn and another provides a very high concentration of Mn at relatively low concentrations of Al. The response of a plant cultivar to changes in the soil acidity induced by lime or acid additions reflects the de gree of Al and/or Mn stress provided by a particular soil, and the abi lity of the cultivar to tolerate those stresses. Examples are given of the way cultivars with different tolerances to Al and Mn toxicity res pond to changes in acidity on the soils with different Al and Mn solub ility characteristics. The utility of this screening technique to defi ne the tolerance of cultivars to acidity on classically different soil s is highlighted.