Soil acidity and growth of a legume. I. Interactions of lime with nitrogen and phosphate on growth of Medicago sativa L. and Trifolium subterraneum L.

Abstract

Lucerne grew poorly without lime on several acid soils on which subterranean clover grew normally. On the moderately acid soils, of pH 5.5–6.0, most of the lime response by lucerne could be attributed to improvement in nodulation and could be eliminated by supplying ammonium nitrate. Strains of medic Rhizobium differed in ability to nodulate lucerne plants in acid soils sufficiently to suggest practical advantage in selecting strains for superiority in this respect. On the more acid soils, of pH 5.0–5.5, lucerne responded to lime or potassium carbonate even when not nitrogen-deficient. This lime response was eliminated by large applications of phosphate. The interaction between lime and phosphate could indicate aluminium toxicity.