Effect of superphosphate, white clover and stocking rate on the productivity of natural pastures, Northern Tablelands, New South Wales

Abstract

The species frequency, pasture availability and animal production on natural pastures oversown with white clover were examined over the five year period 1968-73. Superphosphate was applied annually at different levels (0, 250 and 500 kg ha-1) and the plots were grazed continuously at two stocking rates (7.8 and 15.6 wethers ha-1). An increase in the frequency of white clover (Trifolium repens) and a decrease in bare ground, Panicum spp-Eragrostis spp. and Sporobolus elongatus (in the case of the latter two the effect was particularly evident at the low stocking rate) followed the application of superphosphate. Increasing stocking rate resulted in a reduction in white clover and an increase in the frequency of Panicum spp.-Eragrostis spp. and bare ground. Pasture availability and animal production were increased by superphosphate. Apart from the first year, when the season was unusually dry, supplementary feeding was minimal on all topdressed treatments but was essential at the high stocking rate where no superphosphate was applied. Over the five year period animals on the pastures receiving superphosphate averaged 15 per cent heavier and gave 18 per cent more wool than those that were unfertilized. Wool production at the high stocking rate averaged 17.8 kg ha-1 (49 per cent) more than that from the low stocking rate.