The Effects of Grazing Management and Sulfur Fertilizer on Pasture and Animal Productivity in the Wet Tropics

Abstract

An experiment was carried out over a three-year period in South Sulawesi, Indonesia, to investigate the effects of stocking rate and the application of sulfur fertilizer on productivity of beef cattle grazing native and oversown pastures. At the native site two fertilizer treatments were imposed (0 or 30 kg S ha⁻¹ yr⁻¹ applied as elemental S) in conjunction with two stocking rates (0.5 or 1.0 A.U. ha⁻¹, where A.U. represents a heifer of 110-150 kg body weight), while at the oversown site four fertilizer treatments (annual applications 0 kg ha⁻¹ or 15 or 30 or 30 year 1, 15 year 2 and 15 year 3) were used in conjunction with stocking rates of 1.0 or 2.0 A.U. ha⁻¹. A basal application of triple superphosphate (TSP) was applied to all treatments at the beginning of the third year. ... The results demonstrate that the quality and to a lesser extent the quantity of feed on offer are the major factors restricting animal productivity in the wet tropics. Attempts to manipulate feed quality in this experiment through fertilizer application were unsuccessful due to the rapid disappearance of the legume component. Sulfur fertilizer failed to suppress the 'Imperata' population because only a small amount of legume existed in the pasture and this was not competitive enough. The selective behaviour of the experimental animals further reduced the availability of the legume. Variations in liveweight gains were also related to changes in the quantity of feed on offer and this, in turn, could be related to variations in rainfall. It is suggested that more competitive legumes need to be identified and tested under grazing situations similar to the present experiment.