Seedling raising technique of macadamia nut

Macadamia nuts are propagated by grafting and cutting.

(1) raising seedlings by grafting

1. Seed selection

The seeds used to raise rootstock seedlings should be taken from plants with strong growth, stable and high yield, preferably disease-free and good nut quality. Both smooth shell species and coarse shell species can be used in some areas because of their fast germination and growth, disease resistance and soft wood, so they are easy to be grafted. New Zealand and other places believe that using coarse shell species as rootstocks can improve the cold resistance of macadamia nuts. D4 is mainly used in Australia.

two。 Seed storage

Seeds can be stored in 5-10 ℃, in shaded wet sand, or in sealed plastic bags and refrigerated in the refrigerator.

3. Rootstock cultivation

The vitality of nuts ripened in the high temperature season decreased rapidly, from 100% germination at harvest to 50% after 6 months of storage. Therefore, it is best to remove the outer soft shell and sow seeds after harvest.

The seeds were sown with a hard shell, the suture line was downward, and the sand cover was 2.5cm thick, then drenched with water and kept the seedling bed moist. It began to germinate in 3 to 4 weeks at 30: 35 ℃. If it was less than 24 ℃, the germination time would be more than twice as long. Attention should be paid to the prevention of ants and rodents during rootstock cultivation. When the leaves are ripe, move the seedlings to a plastic bag or other container and shade 50%. The seedlings are very sensitive to water fluctuations, so they must be given adequate irrigation. Trace elements, slow-release and low-phosphorus fertilizers should be applied at seedling stage. The plant was cultured into a single stem and could be grafted after 12-15 months. The terminal bud of macadamia nut is easy to be damaged by high temperature or insect pests, which stimulates its lower bud to sprout many lateral branches, which affects the normal growth of rootstock seedlings. Therefore, attention should be paid to cutting off branches and maintaining single stem extension growth.

Sowing and sprouting substrate should use clean, insect-free coarse river sand, at least 20 cm thick. The seedling soil is made of sand, loam, moss and fully mature sawdust or mushroom residue. Rotten macadamia nut shells can also be used. The pH value of seedling soil was 5.5-6.5.

4. Grafting

Grafting macadamia nuts should not only master the basic techniques of grafting, but also require the scion to fully mature and choose a good grafting time. The low grafting rate is largely caused by improper selection of scions. Therefore, in foreign countries, grafted seedlings are mainly carried out by mature workers in large commercial nurseries.

The main results are as follows: (1) the grafting period is better in spring and autumn, especially in late autumn and early spring.

(2) under grafting conditions, the thickness of scion and rootstock is 1-1.3 cm, which should be fully mature, with light brown to gray bark and protruding lenticels. If possible, the scion should be girdled 6-8 weeks before grafting. The specific method is to select the long branches of appropriate thickness, peel about 2.5 cm wide at the base, and scrape off the cambium tissue. Its purpose is to increase the accumulation of photosynthate in scion and improve the survival rate of grafting. It is better to select dense node buds when grafting. The rootstock is soaked with water before grafting.

(3) grafting methods such as branch grafting, split grafting, joint grafting and cutting grafting can be used. The lower part of the split scion is wedge-shaped, the top of the rootstock is split from the middle, and the scion is cut into a notch to align the rootstock and ear into a layer, tie up and seal the joint. It is considered that this grafting method is the most successful in China. According to our experience, the key to the success of splicing and splicing is that the joint surface should be longer, reaching 1 to 1.5 centimeters. The section is too short to heal. This may be related to the water transport of rootstocks and scions. The patch bud grafting method is also used, and the patch bud grafting method is the most successful abroad.

After grafting, it should be shaded and protected from the sun, and often drenched with water to keep the soil and air moist, and wipe off the anvil buds in time. The scion can sprout 25-30 days after graft. if there are more buds, only one of them with strong growth will be left and the rest will be erased. When the seedling is 70 cm high, it will top, promote lateral branches, and cultivate high-quality seedlings with multiple branches.

(2) Cuttage seedling

Medium coarse river sand with clean and good drainage performance is used for bed insertion.

Cuttings are taken when the level of carbohydrate accumulation in the tree is the highest. The winter and spring season is the best in South China, during which the air temperature is low and the soil temperature is high, which is conducive to rooting. The rooting of cuttings is poor in summer. The cuttings were cut into about 15 cm long, the upper leaves were left with two rounds of leaves, and the lower leaves were all cut off. The base was soaked in indoleacetic acid (IBA) solution containing 300 mg indoleacetic acid (IBA) per liter of water for 30 seconds, dried and inserted into the seedbed 8 cm deep. After insertion to shade, maintain a constant temperature, preferably under foggy conditions.

The cuttings should keep the leaves intact, and partial removal of leaves is disadvantageous to survival and rooting. But there are differences between varieties. Macadamia nut cuttings take root for a long time, and the root primordium can not be seen until about 60 days after insertion. As long as the cuttings take root, the root system is more developed and grows rapidly. Rooting cuttings should be moved to the nutrition bag in time to properly supplement the light and various nutrients needed for growth and development.