Subterranean clover pasture responses to lime application on the acid soils of southern New South Wales

Abstract

The effects of soil amendment with shallow (0-10 cm) incorporated lime or dolomite were examined at 3 sites with acid soils over 6 years. Measurement was made of soil pH and exchangeable cations, and of subterranean clover dry matter production, seed set, and concentrations of calcium, magnesium, manganese, nitrogen and phosphorus. Application of lime or dolomite increased the production of dry matter, but not by the alleviation of molybdenum deficiency. Response in yield ranged from nil to 47%, with most responses in the range 20-35%. Such responses persisted for 5-6 seasons following lime or dolomite application. Differences in soil pH associated with liming were maintained for the 6 years of measurement, so that the benefits in pasture production from soil amendment are likely to accrue beyond the time span of this study. The analyses of plant dry matter indicated that manganese toxicity may have been a factor in the response to lime at 1 harvest, and that higher nitrogen concentration was associated with liming at another. Generally, the plant analyses did not indicate a clear mechanism for the plant responses to lime, although the soil analyses indicated the presence of exchangeable aluminium in the unamended plots at all 3 sites. The plant responses demonstrated that acidity constrained the yield of subterranean clover grown on these soils.