I. J. PARTRIDGE
Department of Agriculture, Sigatoka, Fiji
Liveweight gains (LWG) of steers were measured over eight years from mission grass pastures, most of which were fertilised and oversown with siratro (Macroptilium atropurpureum) and stylo (Stylosanthes guianensis), on steep hill land in southwest Viti Levu. The pastures were fertilised with nil, low and high levels of superphosphate and grazed with 6, 6 and 12 stocking rates respectively, ranging from 0.9 to 3.5 steers ha-1.
Maximum annual LWG recorded was 520 kg ha-1 from high fertiliser at 3.5 steers ha-1, over four years. Applying low and high rates of superphosphate regularly increased annual LWG head-1 from an average of 94 kg in the nil treatment to 121 and 143 kg respectively, at a common stocking rate of 2 steers ha-1. These increments were reduced to 4 and 23 kg head-1 for the 2 years after fertilising ceased. Applying fertilizer in the final year lifted these increases, except on some highly stocked and fertilised treatments where invasion of undesirable weeds confounded results.
Increasing stocking rate by each additional beast per ha reduced LWG by an average of 16 and 30 kg head-1 with nil and low fertiliser but had no significant effect on heavily fertilised pasture until the final year.
The patterns of LWG through the year were similar in all treatments but fertiliser and, in some cases, stocking rate affected the level of gain.
The marginal LWG ha-1 from increasing the stocking rate on unfertilised mission grass from 1 to 2 steers ha-1 was almost double that from applying low fertiliser. Marginal LWG from applying high fertiliser exceeded that from low fertiliser only when the stocking rate was greater than 2 steers ha-1.
Practical recommendations for developing mission grass pastures on steep hill land are given.