Effects of sulfur on five annual grassland species

Differences in yield, sulphate-sulfur (SO₄-S) concentration, and total sulfur (S) up-take were found among five competing annual grassland species growing at different levels of available S at Hopland. Yield response of subclover, soft chess and ripgut to S fertilization increased as the season advanced, but the concentration of total S and SO₄-S in the plants decreased. Sulfur deficiency was indicated by the SO₄-S concentration in each of the species where no S had been applied. The SO₄-S concentration in subclover at flowering gave the best single indication of S status when all levels of available S were considered. Where no S was applied, there was little or no uptake of S after the first harvest date, but where S was applied, it continued to be absorbed by subclover, soft chess and ripgut up to the third harvest. The increase over the check was much greater for subclover than for any of the other species.