ONE of the longest-running agroforestry trials in Australia has delivered some valuable results on running trees and stock together.

The trial was established at Carngham, 25km west of Ballarat, in 1983 by the Victorian Forests Commission and Department of Agriculture. More recently, it has been monitored by the Department of Primary Industries.

    AT A GLANCE
  • Who: Tim Jackson
  • What: agroforestry
  • Why: long-term result shows benefits
  • Where: Cargham, Victoria

It is one of the longest-running agroforestry trials in Australia and unlike plantation forestry, has tested several configurations of grazed pastures and pruned radiata.

DPI forestry officer Tim Jackson said the results compared various systems for wool and sheep production using Merino wethers for up to 25 years after the trees were planted.

"The most productive agroforestry system for grazing consisted of 60 trees per hectare widely spaced throughout the pasture," Tim said.

"This system also produced the largest, most valuable, clearwood logs."

Systems with more trees per hectare had lower agricultural production but greater total wood production.

Total wood production was greatest in plantation blocks with no agricultural component, but individual logs were smaller and less valuable.

Tim said he hoped to be able to complete a detailed cost-benefit analysis on the trial at some stage.

A comparison of two systems, each of 200 trees per hectare, showed that arranging the trees in belts allowed greater agricultural production than spacing them widely throughout the pasture (one stem per 50sq m).

However trees in belts produced less wood due to competition among the closely spaced trees.

"There are trade-offs between animal production and wood production, and also between log quality and wood volume," Tim said.

"Overall profitability depends on many factors in the forest component, such as establishment costs, rotation length, wood volume and log qualities.

"It also depends on factors in the agricultural component, including sheep stocking, wool production and liveweight gain."

Varying wood, wool and sheep prices also had a major bearing on profit.

Tim said the results would probably be the same with eucalypts instead of radiata, although it would depend on the species.

Shallow-rooted sugar gum, for example, would have a greater affect on pasture growth than a deeper-rooted species such as spotted gum.

He said agroforestry provided a great opportunity to get the environmental benefits of trees on farms while producing commercial wood products.

It could also provide extra income, better shelter, greater carbon storage, better soil protection and better habitat for wildlife.

Commercial products from trees include wood, fibre, energy, eucalyptus oil and ecosystem services, Tim said.

"Experienced agroforesters believe that 10 per cent of agricultural land can be planted to trees without loss of agricultural production, he said.

"And as an alternative to plantation forestry, agroforestry can have lower establishment costs, greater viability in areas of lower rainfall and more frequent income."

Long-term results of the Carngham agroforestry trial are available by phoning Tim on (03) 5573 0976.