I.J. PARTRIDGE and J.W. WRIGHT

Queensland Department of Primary Industries, Bundaberg, Queensland, Australia

Abstract

Wynn cassia is a new forage legume which was untested with grazing animals prior to its release in 1984. Wynn cassia was sown into two 24 ha paddocks of black speargrass and, in an unreplicated trial lasting 5 years, steer growth was compared between Wynn cassia paddocks, with and without superphosphate (55 kg/ha/yr), and with a 75 ha native pasture paddock, all at a common stocking rate of 2.4 ha/steer.
Unfertilised Wynn cassia spread rapidly and, despite its reputation for low palatability, provided at least 16% of the steers' diet. Steers on Wynn cassia gained an average of 35 kg/hd/yr more (40%) than those on native pasture. Wynn cassia responded strongly to superphosphate but weight gains improved by only a further 10 kg/hd/yr.
Wynn cassia increased the N concentration of the associated spear grass by 20% when unfertilised, and by nearly 40% when fertilised. On the granodiorite soil at this site, P was generally adequate for plant and cattle but sulphur appeared deficient.