Nutritional restraints on subterranean clover grown on acid soils used for crop-pasture rotation

Abstract

Lime, N and molybdenum fertilizers were used to establish how soil acidity limits the growth of subterranean clover (Trifolium subterraneum), in pot culture, on acid soils taken from north-east Victoria. The results indicate that two nutritional factors associated with the growth of subterranean clover are affected by excess acidity. These are manganese toxicity and ineffective nodulation of the clover. The plants grown on one unlimed soil (Rutherglen) had manganese concentrations and symptoms consistent with manganese toxicity. Liming the second soil (Lilliput) overcame a N deficiency by way of increased nodule formation. A third nutritional factor commonly associated with excess acidity, and found on the Lilliput soil, molybdenum deficiency, was not alleviated by the application of lime. Instead, the application of molybdenum fertilizer gave increases in clover dry matter production at all lime rates. In the absence of molybdenum fertilizer, the molybdenum concentration of the herbage was extremely low, irrespective of liming. These results are discussed in relation to already established field responses of subterranean clover to lime, and the management of the clover-ley system on the strongly acid soils.