Industry information – Macadamia farming in Australia
Macadamia Farming in Australia
Macadamia farming is like all horticultural production systems – rewarding and challenging at the same time! Macadamias are a long-term crop taking on average four to five years from planting before cropping commences, seven years before commercially viable yields are produced and 12 years before breakeven.
Each season varies, but typically a yearly cycle looks like this:
- Flowering commences in August and continues through September. Depending upon weather conditions, this can happen earlier or later.
- Nutlets grow from the flowers, with only 1-2% of all flowers turning into nutlets. Over the spring period the nuts continue to grow in size and reach full size in late November-early December.
- Once nuts have reached full size, the shell begins to harden during December and early January.
- After the shell has hardened off, the oil accumulation phase begins. This phase lasts for about two months.
- In Northern NSW mature nuts begin to fall in early March (late February in Bundaberg and late March in NSW mid North Coast) and continue to come down over the next 6 months. The peak of nut drop is typically late May and June.
Macadamia Nut-in-Husk Hanging on a tree
Macadamia farmers harvest the nuts after they have fallen to the ground – completing a harvest round every two to four weeks. Harvesting frequently ensures the highest nut quality is maintained. The most common harvesting machine uses segmented wheels with fingers on the end that roll over the ground, capturing the nuts between the fingers and picking them up. The harvested nuts are collected in a bin on the harvester.
Harvested nuts have a fibrous outer layer called a husk which must be removed before the nut is sent to the processor. Farmers take the harvested nuts to a shed where a machine called a dehusker removes the husk. Some farmers have a dehusker fitted to their harvester so they can complete this task in the field.
Macadamia Finger Wheel Harvester
Once the nuts are dehusked, the farmer inspects them for obvious defects and removes any rejects from the batch. The sorted nuts are then stored on-farm in drying bins or silos until enough quantity is accumulated to make a load. The nut is then transported to the factory where it is weighed, sampled and tested for its quality. The grower is paid on the amount of nut-in-shell they deliver (calculated at 10% moisture content) and the quality of the kernel they produced.
At the end of the harvest season, farmers prune their trees to allow sunlight to penetrate through the canopy for better crop yield – and to reach the orchard floor for maintaining groundcover. This pruning may include hedging with a machine with a set of large rotating saws that cut off the sides of trees as it drives along the row. It may also include selective limb removal using a chainsaw or pole saw to allow light to penetrate into the trees. Depending upon row spacing, farmers will determine what pruning strategy best maintains productivity in their orchard and retains ground cover. In older orchards on close row spacings (eg, 7 metres x 4 metres) where trees have become very large, production can drop if little light penetrates into and through the tree. In this case, farmers will often remove tree rows allowing the trees left behind to ‘relax outwards’ and produce more horizontal branches. This strategy has been shown to let more sunlight into and through the tree canopy, and to encourage more grass to grow on the orchard floor. It is one way of ensuring long term viability of production.
A Hedger trimming the side of a macadamia tree
During the off-season (when harvesting is not happening) farmers will also spread organic rich material under their trees to act as a mulch. This mulch is used to maintain a healthy soil environment and promote tree root growth – to ensure sustainable production.
Once flowering commences growers utilise the services of professional crop scouts to monitor the flowers and developing crop to ensure pests and diseases are managed. The crop scouts use an integrated pest management system for determining if control of pests or disease is required. Only if economically-significant damage is being caused will they recommend a control is applied.
The macadamia industry is focused on ensuring it uses as little chemical control as possible – it has invested heavily in research and development to find biological control options such as trichogramma wasps for Macadamia Nutborer control. This tiny parasitic wasp lays its eggs into the macadamia nutborer’s eggs and halts the formation of a damaging caterpillar. Once the critical period for macadamia nutborer is upon farmers, they will release the trichogramma wasps into their orchard to ensure the levels are high enough to give adequate control. Since the use of trichogramma wasps, most farmers have found they do not need to use chemicals for macadamia nutborer control.
A Trichogramma wasp laying its egg into a Macadamia Nutborer egg (Photo courtesy Craig Maddox, NSW DPI)
During the off-season farmers will also carry out repairs and maintenance to machinery and undertake any major works required such as the installation of drainage lines in the orchard, soil profiling to cover exposed roots and planting of groundcovers.