Effect of species and cultivation on the responses to phosphate of annual pastures and crops

Abstract

Three crop species, sand-plain lupin, Lupinus cosentinii L. (cv. Chapman), narrow-leaf lupin, L. angustifolius L. (cv. Uniharvest), and wheat, Triticum aestivium (cv. Gamenya), were grown under field conditions in soil fertilized then cultivated to 10 cm depth. Two annual pasture species, subterranean clover, Trifolium subterraneum L. (cv. Daliak), and Wimmera ryegrass, Lolium rigidum Gaud. (cv. Wimmera), were also grown in the field both with and without cultivation. All species were fertilized with seven levels of phosphate broadcast on the soil surface before cultivation. The amount of phosphate which produced 90% of maximum yield depended on species and cultivation practice: wheat required 98 kg phosphorus/ha; L. angustifolius, 65 kg/ha; L. cosentinii, 42 kg/ha; subterranean clover, after cultivation, 49 kg/ha; subterranean clover, not cultivated, 28 kg/ha; Wimmera ryegrass after cultivation, 40 kg/ha; Wimmera ryegrass, not cultivated, 18 kg/ha. All species except wheat required less current phosphate in this experiment than they did 3 years earlier on the same site in virgin soil. Cultivation changed the distribution of soil phosphate, and the roots of the pasture species followed the phosphate distribution.