Effect of aluminium on the growth chemical composition of some tropical and temperate pasture legumes

Abstract

The effects of aluminium (0, 0.5, 1.0, 2.0 p.p.m.) on the dry matter production (tops and roots) and chemical composition of five tropical and six temperate pasture legumes grown in a cultu1.e solution containing 2 p.p.m. phosphorus were ascertained. The tolerances of the tropical species to aluminium were in the order Desmodiunz uncinatum = Macroptilium latlzyyuoides = Lotonis bainesii = Stylosanthes humilis = Glycine wightii > Medicago sativa, and temperate species in the order Trifolium rueppellianum= Trifolium sernipilosum > Trifolium repens = Medicago scutellata = Medicago truncatula = Medicago sativa. In the tolerant species the yield of plant material from the 0.5 p.p.m. aluminium treatment was greater than from the control. The top/root weight ratios of the tolerant species were unaffected by treatment; the ratios of the sensitive species were reduced. The effect of aluminium treatment on aluminium, nitrogen, phosphorus, potassium, calcium, magnesium, and sodium concentrations in the plants are given. The principal nutrients to be affected were calcium and phosphorus. Aluminium treatment reduced the calcium concentrations in the tops of all species and there were reciprocal relationships between calcium, magnesium, and potassium concentrations. In the sensitive species aluminium treatment reduced phosphorus in the plant tops and roots; in some of the tolerant species the intermediate aluminium treatment increased the phosphorus concentration in the plant tops; however, the high aluminium treatment reduced the phosphorus concentration.