Pinus radiata and sheep production in silvopastoral systems at Carngham, Victoria, Australia

This long term experiment provides production data for evaluation of combined forestry and livestock systems. Five systems were established in Pinus radiata planted in 1981 (620 mm average annual rainfall). Sheep were introduced in 1984 and trees were pruned in several lifts. Adjusted tree stockings were (1) 60 widely spaced trees ha⁻¹, (2) 200 widely spaced trees ha⁻¹, (3) 200 trees ha⁻¹ in five-row belts, (4) 1,090 trees ha⁻¹ (unpruned) and 815 trees ha⁻¹, and (5) no trees (open pasture). Tree growth, wool production, liveweight gain and pasture production were measured. At year 25, tree diameter under bark at 1.3 m (DBHUB) in Systems 1, 2, 3 and 4 (unpruned) was 46.0, 39.2, 33.5 and 24.1 cm, while volume of bark-free 6-m butt-logs was 49, 117, 86 and 233 m³ ha⁻¹. Inner rows of System 3 belts contained smaller trees than outer rows. Pruned System 4 trees had slightly greater diameter than unpruned trees. Pasture production declined with tree stocking and time, due to shading and competition. Wool production (WP ha⁻¹) and liveweight gain (LWG ha⁻¹) declined linearly from year 9 to 17 with increasing disparity among systems. In 1998 (year 17) WP ha⁻¹ in Systems 1, 2 and 3 was 64, 16 and 43% of that in open pasture. Further analysis is needed to evaluate the financial costs and returns of various systems under particular rotation lengths and market prices.