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Thứ hai, 06.04.2015 14:44
Cultivation of macadamias
Macadamias can be produced successfully in areas where avocados, papayas,
mangoes and bananas do well.
The trees flower during spring from August to September.
The further development of the fruit lasts 31 weeks.
Select high-quality nursery trees by inspecting the:
· plant container and roots
· soil mixture
· graft union
· shape of the tree.
Plant container and roots
Distorted root systems
Climatic and soil requirements
Most soil types are suitable for the production of macadamias, provided they are well drained and have no restrictive layers in the top 1 m of the soil. Poorly-drained clay soils are not suitable.
The ideal temperature for macadamias is between 16 and 25 °C. Although the trees can survive when temperatures drop below 3 °C, they should not be regarded as frost resistant.
Height above sea level
Height above sea level influences nut quality and production. Production declines dramatically above 600 m. Above 640 m growth is slower and trees take longer to produce.
Cultivars suitable in areas between 600 and 640 m above sea level are Mauka, Kau and Keaau.
Cultivars recommended nearer to the coast, 90 to 300 m above sea level, are Purvis, Makai and Keaau.
The cultivars recommended are: Keaau, Kakea, Kau, Purvis, Pahala, Mauka and Makai. They are regarded as superior to Nelmak 1 and Nelmak 2 for commercial processing and marketing. Their oil content is usually higher than 73 % and the sugar content is low enough to ensure an even, cream colour after the nuts have been baked. Under ideal circumstances the crack-out percentage will be higher than 40 %.
· If the physical properties of the soil, namely depth (0,81,0 m), drainage, etc are suitable for growing macadamias, the soil must be prepared carefully and well in advance.
· The soil must be loosened as deeply as possible. It should then not be necessary to make large planting holes.
· If the soil in the planting holes is compacted, the roots could become rootbound.
· An investigation should be done after the planting of macadamia trees to ensure that root growth is not restricted.
· Do not fertilise recently planted trees. They must first become well established and grow vigorously. It is wise to wait one year before applying fertiliser.
· Macadamia cultivars have different growth patterns. They are usually either spreading or upright growers.
· The size of each cultivar's drip area (surface area below leaf canopy) depends on the altitude, soil type, rootstock, rainfall, temperature and relative humidity.
· The planting distance for each cultivar will therefore differ from place to place. Various guidelines can be followed with respect to spreading and upright growers.
As soon as the competition for light becomes too great, production will decrease.
To allow for tractors to move between the trees, the hedgerow planting system is used. With this system:
· Upright growers are planted 3,5 m apart within the row with 7 m between rows.
· Spreading cultivars are planted 10 m apart within the row with 6 m between the rows.
Tree shape of some macadamia trees
Various tree shapes
Other crops are sometimes cultivated between young macadamia trees. There are 3 main aspects to be considered before planting an intercrop.
· Cultivation of the intercrop could damage or adversely affect the growth of the tree or injure roots and should be avoided.
· Tall-growing plants could crowd out or overshadow the young macadamia trees and should not be planted.
· No other crops should be planted between bearing macadamia trees. Once this stage has been reached, the macadamia trees should receive the attention and treatment necessary to ensure maximum growth and production.
· Macadamia leaf samples must be taken during October and November. The time of sampling is critical. The correct leaf must be sampled.
· When submitting a leaf sample from a particular orchard for the first time, it must be accompanied by a soil sample. Thereafter it is advisable to send in soil samples annually. It is essential to consider the results of both soil and leave samples when making fertilisation adjustments.
· Only leaves from healthy plants must be sampled. They must be free from sunburn, insect damage or any deficiency symptoms or signs of disease.
Method of sampling
Do not fertilise young, transplanted trees too soon. They must first become well established and start growing vigorously before any applications are made, preferably after at least 1 year.
Never apply fertilisers against the stem of young trees.
Fertiliser must be broadcast evenly from about 0,2 m from the stem to about 0,5 m outside the drip area of the tree.
Macadamia trees are very sensitive to root damage, therefore each fertiliser application must be followed by a light, controlled irrigation.
Fertilisers must not be worked into the soil.
When the trees are established and start growing, fertiliser must be applied regularly according to the table.
Quantity of fertiliser according to age (kg/tree/year)
Zinc and boron sprays
Because most soils are naturally low in zinc, or the zinc is not available, this element must be applied every year. The following concentrations are recommended:
· Zinc oxide at 200 g/100 l water, or
· NZn at 150 ml/100 l water.
Many macadamia orchards are also low in boron and it is desirable to spray the trees every 2 years with 100 g borax or 75 g Solubor/100 l water right from the start.
Water stress often limits tree growth, as well as the set, growth and quality of macadamia nuts. It is important to know how much water to apply and when to apply it if it does not rain.
The approximate water requirements for macadamia trees (mm/month)