ABSTRACT
Summary On undeveloped, acid (pH < 5.0) soils in New Zealand, growth of the conventional legumes white clover (Trifolium repens L.), red clover (T. pratense L.), and alsike clover (T. hybridum L.) is limited by acidity. The objective of this research was to identify an alternative legume species better adapted to both acidity and low inputs of phosphorus (P) and to examine grazing management. Big trefoil (Lotus pedunculatus Cav.) cv. Grasslands Maku and birdsfoot trefoil (L. corniculatus L.) cv. Maitland were examined. Seed was inoculated with appropriate strains of rhizobia and sown into undisturbed tussock grasslands on acid soils of low P status at altitudes of 550-880 m. Lime and phosphorus treatments were broadcast. Herbage yields were measured by mowing or by pregrazing and postgrazing ground-level cuts in animal-grazing studies. Big trefoil gave 2-3 times the yield of white and red clover and birdsfoot trefoil. While broadcast lime increased yields of white clover (but not of big trefoil), the yields remained lower than those from big trefoil. Big trefoil gave markedly higher yields than white clover at light rates of P (7.5-10 kg/ha) and was responsive to the heaviest rate applied (60 kg/ha). White clover did not respond to rates of P greater than 15 kg/ha. Lack of P response by white clover is thought to be due to high levels of exchangeable aluminium present in the soils. A grazing-management study on established swards showed yields similar under close defoliation (2.5 cm) with sheep and lax (7.5 cm) defoliation by cattle. These studies demonstrate a large potential in New Zealand for the development of native grasslands on acid soils of low P status by oversowing with big trefoil.
