Pasture, sheep and timber production from agro-forestry systems with subterranean clover sown under 15-year-old Pinus radiata by a method simulating aerial seeding

Abstract

A fifteen-year-old plantation of P. radiata at Mundaring, Western Australia, was thinned to densities ranging from 0 to 200 trees/ha, and pruned to 6 m. Subterranean clover cv. Seaton Park was sown with fertilizer by a method simulating aerial seeding. Pasture, sheep and tree growth and changes in soil and foliar nutrient levels were measured over a four year period. Clover establishment was most satisfactory. In the second year the pastures under tree densities of 150 or more trees/ha carried 60% of the numbers of sheep carried on the pastures with no trees. Two years later, following increased canopy growth and shading, this relative carrying capacity was down to 40%. After four years, soil and foliar nutrient levels were not affected by tree density. At the lowest density of trees (< 100 stems/ha), individual tree diameter growth and volume production per hectare were stimulated and there was least loss of agricultural productivity. This density was therefore preferable for agroforestry.