The effects of sulphur and phosphorus on the yield and composition of some indigenous and naturalized legumes on the North-West Slopes of New South Wales.

Abstract

Indigenous, naturalized and commercial legume species were grown in pot culture, at five levels of applied sulphur as sodium sulphate (0, 10, 15, 25 and 35 kg ha-') and phosphorus as sodium dihydrogen phosphate (0, 6, 15, 23 and 29 kg ha-'). The dry matter yield and sulphur and phosphorus concentration in the plant tops were determined and critical percentages of sulphur and phosphorus established. In the presence of adequate sulphur and phosphorus the species yields ranked in the order Trifbliunz rubtcrranertrn L > T. glorneratum L > Medicago trumatula J Gaertn > M. polymorpha L 2 M. minima L (Bart) > Gl,wiize tabacirza (Labill) Benth, but only for the Trifolium species were both sulphur and phosphorus essential for high yields. Sulphur deficiency symptoms of chlorotic leaves were observed in the So treatments for all species except G tabac~m In general sulphur deficiency in these species was indicated by sulphur content less than 0.2%, a nitrogen to sulphur ratio greater than 20.1 in the plant tops and a low proportion of laminae. No phosphorus deficiency symptoms were observed in any of the species growing in the Po treatments, though phosphorus percentages ranged from 0.15-0.22. The critical sulphur and phosphorus percentages in the plant tops of these species at flowering ranged from 0.17-0.32 for sulphur and 0.24-0.32 for phosphorus.