A comparison of fertilizer programmes for the development and maintenance of sown pasture on a sulphur deficient basaltic soil

Abstract

Calcium sulphate was applied initially at rates equivalent to 0, 8.4, 16.8, 33.6 or 50.4 kg sulphur ha-1 to an existing subterranean clover (Trifolium subterraneum) -phalaris (Phalaris tuberosa) sward. At two of these rates, 8.4 and 33.6 kg sulphur ha-1, four maintenance levels (0, 8.4, 16.8 and 33.6 kg) were applied in each of the succeeding three years. In the production of dry matter, most efficient use of the fertilizer was made when the requirement of the pasture (33.6 kg S ha-1) was fully met in the first year, and subsequent annual dressings were made at the rate of 8.4 kg S ha-1 a year. Plant response was related to the level of sulphur available, and the success of particular programmes depended on the rapidity with which the potential yield of the pasture was realized under them. There was evidence, with the change from clover to grass dominance, that grass made more efficient use of residual sulphur in producing dry matter than did clover. Low maintenance rates were effective because they enhanced the residual value of the initial application.