Effectiveness of elemental S fertilizers on forage grass

Abstract

Two field experiments were conducted from 1993 to 1995 to compare the effectiveness of various cumulative elemental S and sulphate-S fertilizer applications in increasing dry matter yield (DMY) and S uptake of forage grass. In exp. 1, one sulphate-S (Na 2 SO 4 ) and two elemental S (Agric-Grade 0-0-0-95 and Tiger 90) fertilizers were applied annually to grass in mid to late April at 10, 20, 30, 40 and 50 kg S ha −1 rates. The increase in DMY from S application was significantly lower with elemental S fertilizers than with Na 2 SO 4 in the first and second years, but in the third year elemental S fertilizers had DMY increase similar to Na 2 SO 4 In exp. 2, a number of elemental S and sulphate-S fertilizers were applied annually to grass in mid- to late April at 15 kg S ha −1 rate. There was a marked increase in DMY from S application in all the 3 yr with the three sulphate-containing S fertilizers (Na 2 SO 4 , K 2 SO 4 and CaSO 4 ). When elemental S fertilizers were used, only Turf-Grade 0-0-0-95 increased DMY in all the 3 yr and it produced DMY increase similar to the sulphate-S fertilizers in the third year. Elemental S Prills did not produce any significant increase in DMY in any of the 3 yr. Other elemental S fertilizers [e.g., Elemental S Powder, Agric-Grade 0-0-0-95 and Tiger 90] increased DMY in the third year only, but this increase was still less than the sulfate-S fertilizers. Turf-Grade 0-0-0-95 (with smaller granules) produced greater DMY increase than Agric-Grade 0-0-0-95 (with larger granules) in all the 3 yr (though significant in the third year only). The S fertilizers that contained small amounts of sulphate-S in addition to elemental S were generally more effective in increasing DMY than the similar fertilizers containing only elemental S. The increase in S uptake from applied S in grass showed usually similar trends as DMY increase. In conclusion, the results suggest that some elemental S fertilizers can be as effective in increasing forage DMY on perennial grass as sulfate-S fertilizers. However, depending upon soil type and climatic conditions two or more growing seasons may be needed for S in the elemental S fertilizers to become fully available to the plants. Key words: Elemental S fertilizers, forage yield, grassland, sulphate-S fertilizers, sulphur uptake