The macadamia nut tree is native to Australia where it naturally grows in the wild. Macadamia nut is an important high value export market cash crop that is quickly gaining popularity among farmers around the globe. It is currently among the fastest growing agricultural practices with Australia, South Africa and America (Hawaii) leading the world production. Macadamia nuts farming is capital intensive and requires a long term financial investment period before positive returns. This is because the macadamia tree takes five to twelve years to produce nuts. However, once established a good tree can produce nuts for about 50 years. It is therefore of paramount importance for farmers to acquire necessary skills and knowhow about macadamia nuts farming to achieve a successful harvest from the onset.
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Macadamia nuts farming succeeds in warm subtropical climates with temperatures ranging from 17oC to 27oC and mean annual rainfall of about 700mm to 2600mm. The macadamia tree is susceptible to extreme hot weather conditions as well as frost. It can survive temperatures below 3oC but it is important to note that the tree is not frost resistant. Macadamia nuts farming demands an altitude of approximately 1000m to 2000m although it can still thrive at much lower altitudes. Under ideal climatic conditions, the tree can grow up to 12m in height and 45cm in diameter.
Macadamia nuts farming can be practiced in a range of soil types, provided they are well drained and have no restrictive layers in about a meter of the top soil. It is most suited to deep, permeable loams and sandy loams with good organic matter content which allows optimal root growth. The soils should have a pH of 5 to 6.5. Macadamia nuts farming tends to fail in areas where soil or water has high salt concentrations. If the soil is compacted, the roots could become root-bound. For this reason, it is important to loosen properly prior to planting. Poorly drained soils puts the trees at risk of diseases such as trunk canker disease.
A representative sample of soil, down to a depth of at least 3 feet, should be examined so as to determine the fertility of the soil. This ensures that appropriate nutrient supplements are added in their correct quantities for optimal tree growth. Fertiliser should not be added while trees are still young. The recommended time to apply fertiliser is when trees are fully established, preferably after at least a year. Depending on the soil analysis, fertilisers of lime, dolomite, gypsum, phosphorus, copper and zinc can be added 3 months prior to planting. Fertiliser must be distributed evenly throughout the orchard from roughly 0.2 m from the stem to 0.5 m outside the drip area of the tree. Macadamia nuts farming requires fertiliser application for 3 to 4 times a year, after planting or in conjunction with mulching or weed control practices.
Macadamia nuts farming involves growing the seeds in a nursey before transplanting them in the orchard where they are nurtured until reaching the harvesting period. The trees can also be planted directly in the orchard, without necessarily keeping them in a nursery. When growing macadamia in the nursery, the size of the container is important. If the container is small, the tree becomes pot-bound and the taproot might be distorted weakening its chances of surviving in the orchard. Seedlings selected for transplanting should have four to 6 hardened leaves. They are carefully lifted from the sand bend to avoid root damage and placed in a bucket of water 10cm deep. Potting bags of 18cm x 15cm are filled with soil mixture while the seedlings are placed at the centre; the seedlings are then watered and moved to a shaded area with only 40% to 50% sunlight. They should be kept for roughly 2 months prior to moving them in an open space where they are nurtured for about more or less a year before grafting. Grafted trees are an ideal variety for commercial farmers as they mature faster than trees grown directly from seedlings. Macadamia grown directly from seed may take up to 8 to 12 years before bearing fruit. Trees grown from grafted seedling however only take 2 to 3 years. In addition, grafted trees tend to produce at least 3 to 5 times greater yield of kernels compared to other tress of the same size and age. Grafted trees take 3 to 4 months before they can be transplanted in the orchard. The spacing between of the seedling should be 4m x 10m or 5m x 10m. However, if they are incorporated with another crop in the field, spacing is altered to just about 9m x 9m or 10m x 10m.
Pests and Diseases
Control of pests and diseases is an important aspect of macadamia nuts farming. Macadamia nuts seedlings are susceptible to scale insects, macadamia felted coccid, macadamia twig-girdler among others. These attack the seedlings, flowers, fruits, foliage and twigs thus negatively impacting the overall yield. Trees attacked by pests and diseases appear stunted, chlorotic and partially defoliated. It is therefore important to inspect trees regularly for any signs of pests and diseases. Farmers should also be on the lookout for rats, hares and kangaroos as they like to feed on macadamia. Registered pesticides should be applied timely before the spread of pests and diseases.
Weed control is usually a serious problem in macadamia nuts farming. Farmers should always make sure that there is no weed around trees. An area of about 1.5 times the size of the tree canopy should be weeded. Registered herbicides as well as mechanical means like hand weeding and slashing can be used to control weed in the orchard. Mulching is a great way to manage weed whilst providing the trees with necessary nutrients. Mulch should be placed 10 to 15cm from the base of a tree. The orchard should be cultivated regularly to prevent competition of water and nutrients between weed and trees.
Macadamia nuts fall from the trees when they are fully mature. Before harvesting, the area around the trees should be cleared to avoid contamination and facilitate efficient collection. It is not advisable to harvest macadamia nuts from the trees because it is difficult to distinguish ripe nuts from immature nuts. The nuts should be picked within 2 to 3 days after falling to prevent physiological deterioration and damage by rodents. During the main harvest season, nuts have to be picked up every 2 to 4 weeks, depending on the weather and the amount of nuts falling. In humid weather, they should be gathered frequently to avoid rot, mould and germination. After collection, macadamia nuts are spread out in layers of about 15 cm on mats or meshed trays under a shade until they are husked. Kernels are the main product of macadamia nuts farming and are sold as various products in confectionary. Shells can be used in manufacture of plastic and husks as mulch, compost or fertilizer. Read more about Harvesting Macadamia Nuts .
With proper management, macadamia nuts farming can yield a bumper harvest for more than 50 years. Although, it is a capital intensive venture, once established macadamia nuts farming is highly profitable. Farmers should ensure their staff is highly skilled in growing macadamia trees as the biggest barrier to success tends to be untrained and inexperienced handlers.