Effect of sulphur deficiency on sulphur and nitrogen levels in pastures and lucerne

Abstract

Clovers, grasses, and lucerne from various trials have been analysed for total sulphur and nitrogen contents. As with nitrogen, sulphur concentrations are higher in leaflets than in petioles in legumes, and higher in leaves than in stem tissue in lucerne and red clover. Levels are higher in younger than in older tissues. The critical sulphur concentration in white clover at grazing height (3–6 in.) is approximately 0.26%. A similar or slightly higher level is indicated for grasses at the young leafy stage. The critical level in lucerne at the hay stage is approximately 0.20% S. In both white clover and lucerne, total nitrogen concentrations increased with yield increases from sulphur nutrient up to about 95% of the maximum yield. Sulphur responses in legumes appear to be due to the nearly simultaneous correction of both sulphur and nitrogen deficiences.