Rainforest trees planted on farms in north Queensland can grow 50 percent bigger within three months of planting and use far less fertiliser, due to an innovative technique developed by CSIRO scientists.

The method is proving so successful it is already being exported to Australia's Pacific neighbours, Fiji, Samoa and the Solomon Islands.

The new technique uses slow release fertiliser within a nursery medium so that the fertilisers are already in the root zone of the nursery seedlings before they are planted.

This technique uses 30 times less nitrogen and 100 times less phosphorus than is currently used by industry on tree seedlings after they have been planted.

In the tropics, tree growth rates are often limited because the soils available for new plantings can be low in nutrients.

According to CSIRO Land & Water's Dr Michael Webb, the surface-applied fertiliser currently used by industry does not appear to reach the root zone of these young trees in an efficient manner.

"The fate of such surface-applied fertilisers in these plantation forest systems is unknown, but probably quite a large proportion is lost by leaching, by adsorption onto the soil, or to competing regrowth," he says.

"Given that 500 hectares of rainforest trees are being planted on farms each year in north Queensland, it is important to overcome these problems."

The results of the research carried out in the Solomon Islands and the Daintree region of north Queensland are so convincing that the new CSIRO technique is already being adopted overseas. It is now standard industry practice in the largest commercial plantation forestry company in the Solomon Islands, Kolombangara Forestry Products Ltd.

The technique is also being refined for local routine use by the Ministries of Agriculture, Forestry, Fisheries and Meteorology in Samoa, and the Ministries of Agriculture, Fisheries and Forests in Fiji.

The technique is currently being demonstrated in north Queensland with funds from the Rural Industries Research and Development Corporation, the Land and Water Research and Development Corporation and the Forest and Wood Products Research and Development Corporation Joint Venture Agroforestry Program and the Natural Heritage Trust.

CSIRO researchers expect this technique may also lower costs for weed control and fertiliser usage, shorten rotation times, increase growth rates and improve survival rates of seedlings.

"Using fertiliser more efficiently makes more sense from an environmental perspective," says Dr Webb.

"Faster tree growth and earlier canopy closure is another benefit for the environment with weed growth decreasing and less need for surface-applied fertilisers."

Dr Webb says another interesting observation from research is that tree seedlings can appear to be healthy even though they may not be growing at their maximum rate due to lack of nutrients.

"This means that farmers may not realise that their trees are not growing at a maximum rate," he adds.

The research was extensively funded by the Australian Centre for International Agriculture Research (ACIAR).

More information:
Dr Michael Webb, CSIRO Land and Water, Phone: 07 4753 8500
Julie Crough, CSIRO Land and Water, Phone: 07 4753 8514; Mobile: 0417 070 915
Jenni Metcalfe, Phone: 07 3846 7111; Mobile: 040 855 1866

Vision opportunities: Photos are available showing the experimental differences in growth between tree seedlings with or without the new CSIRO technique. There are also trials at the CSIRO Davies Laboratory at Townsville and at the CSIRO Laboratory at Atherton. Contact Julie Crough to arrange footage/shots.

Copyright: Dr Michael Webb, CSIRO. Left: Eucalyptus pellita (red mahogany) seedling raised in a standard potting media with no field fertilisers added contrasts dramatically with the same species raised using the "complete" nutrient fertiliser applied at planting.