When to plant Taiwan Indian jujube? A detailed guide to cultivation methods
1 Timing It is usually planted from February to March (in frost-free areas of the south, planting can be advanced to December to February), with a high survival rate and good growth, and it can flower and bear fruit in the same year. After the fruit is harvested the following year, superior varieties are grafted again between February and March.
2 Density Moderate close planting can follow (1) 3m x 4m, 55 plants per 666.7 sq m; (2) 3m x 5m, 44 plants per 666.7 sq m; after 3 years it can be changed to the two methods of 6m x 4m and 6m x 5m.
3 Carry out mixed planting or interplanting Because the pistil stigma of the Indian jujube (which has post-maturation) and the maturation speed of the stamen pollen are not consistent, when planting the main cultivar it is also necessary to mix-plant or interplant 1 to 2 other varieties as pollinizer trees. Pollinizer trees should be chosen from varieties with a large amount of pollen and a high pollen germination rate, and varieties that bloom in the morning should be mixed with varieties that bloom in the afternoon. According to surveys, Huangguan and Biyun are afternoon-blooming varieties (3 to 4 o'clock), while the other known varieties all bloom in the morning (9 to 10 o'clock). When mix-planting, one pollinizer tree can be interplanted every 6 to 7 plants, or one row of pollinizer trees can be interplanted every 6 to 7 rows.
Training and pruning
The side branches of the Indian jujube grow obliquely, so pruning must be done frequently to maintain a good tree structure, keep the tree well ventilated and lit, reduce the occurrence of pests and diseases and improve fruit quality. The Indian jujube also needs annual renewal grafting to continuously improve the planted varieties. Training and pruning can be divided into the following three types: 5.1 Trunk renewal pruning For one-year-old young trees, cut off at 30 to 60 cm above the ground, select 3 to 4 side branches that are robust and evenly distributed as the main branches, guide them in four directions with bamboo poles, and each main branch forms an open-center shape; on the main branches, rib-like side branches form alternately, and the new shoots growing from the side branches can become the fruiting branches of the current year, flowering and fruiting in the leaf axils on the sides of the fruiting branches. During the growth period, remove useless sprouts at any time, and properly prune dense branches, water sprouts and slender branches to facilitate ventilation and light penetration in the canopy. After the second year, carry out trunk renewal and grafting every year from February to March after fruit harvest; saw off the base trunk at 5 to 10 cm above the ground for grafting or renewal, keep 1 new shoot that grows well and is properly positioned as the new trunk for the year, cut off the remaining buds, so that the new main branches grow robustly, and the subsequent pruning is the same as for one-year-old young trees.
Another method is: during spring pruning each year, cut the main branches of the previous year back to 1.5m, and cut off the side branches on both sides, carry out girdling at about 30 cm above the ground at the base of the main branch, keep one strong bud below the girdle near the trunk, remove excess buds, and guide and tie the new shoot sprouted from this bud to the old main branch so that it grows forward and develops into the new main branch of the current year, while the old main branch naturally forms the support of the new main branch. Generally, after the old main branch has been used continuously for two years, it can be sawed off during the fruit harvest period.
Long-shoot pruning In order to make the Indian jujube flower earlier, some fruit growers in Taiwan, after fruit harvest, keep the main branches 1.0 to 1.5m long, and saw off all the remaining branches except those used as supports. After side branches grow out, cut them back to 50 cm and let them sprout small branches, on whose leaf axils flower spikes are borne. With this pruning method, special attention must be paid to cultivating strong fruiting branches, otherwise it will lead to a low fruiting rate and affect fruit quality. However, the plant can bloom from April to May, advancing the production period, and can still bloom and bear fruit successively from August to October.
Pruning and training After trunk renewal pruning each year, the branches and shoots grow vigorously; in June, prune the main branches appropriately again to make them sprout branches, but crossing branches and overly dense branches should be cut off, and branches whose fruiting position is too low should be cut off from the tip, so as to keep the orchard well ventilated and with sufficient sunlight.
Fertilization The Indian jujube undergoes deep renewal pruning every year, so to restore the canopy to its original size, more fertilizer must be applied.
Fertilization timing and amount In the first year of planting, fertilizer should be applied lightly and frequently, with more organic fertilizer (compost, decomposed chicken manure, etc.); during the new shoot growth period, the three elements N, P and K are all important, and more N fertilizer is needed; before flowering, the proportion of P and K fertilizer should be increased. After the second year, the annual fertilization period is generally divided into three applications: April (after the graft has survived or after renewed branches and shoots have grown), July to August (before the full flowering period) and October to November (early fruit harvest period). After the fourth year, the Indian jujube needs more N and K fertilizer, and the application ratio of the three elements N, P and K is about 4:2:5. Before the first fertilization, apply 5 to 8 kg of decomposed organic fertilizer per plant to maintain the needs of new shoot growth.
Foliar topdressing For plants bearing too much fruit, foliar spraying with urea, monopotassium phosphate and a small amount of trace elements is suitable to improve the quality of the jujube fruit.
Prevention and control of nutrient deficiency symptoms Indian jujube planted on acidic soil or sandy soil is more prone to magnesium deficiency and boron deficiency, and measures should be taken to prevent and control them.
Magnesium deficiency symptoms and prevention and control When magnesium is deficient, yellowing appears between the veins of old leaves, then gradually spreads to the whole leaf, while the veins remain green; when magnesium deficiency is severe, the old leaves turn yellow and drop. The following methods can be used for prevention and control: apply more organic fertilizer in the orchard; in orchards with severe magnesium deficiency, apply 15 to 30 kg of magnesium sulfate per 666.7 sq m each year; if magnesium deficiency is found during the flowering period, spray 0.5% to 1.0% magnesium sulfate once every 7 to 10 d.
Boron deficiency symptoms and prevention and control When boron is deficient, the tips of branches and shoots stop growing, young leaves become deformed, in the final stage the top shoots wither, and the veins of the top leaves turn yellow and drop. The fruit flesh at the top of the fruit becomes corky, browns, and forms cavities, causing the flesh to harden, the flavor to deteriorate, and the fruit to lose its commercial value. When the boron content in the soil is below 0.1 mg/kg or the boron content in the tree body is below 2 mg/kg, boron deficiency symptoms may appear. Preventive methods include: from the initial flowering stage to the stage when fruit drop stops, apply a 500-fold solution of water-soluble boron (effective boron 66% or more) or 0.2% to 0.3% boric acid (concentration 99%) plus 0.3% quicklime solution as a foliar spray, once every 14 to 20 d, for a total of 4 to 5 times; after fruit harvest, apply 20 g of borax per plant to the soil, and in areas with severe boron deficiency, an appropriate higher amount may be applied; and apply more organic fertilizer.
Pests and diseases and their prevention and control
1 Diseases The main ones are powdery mildew (damaging new shoot leaves and fruit) and ring spot (damaging leaves). Prevention and control methods: for powdery mildew, use 19.5% Bai Fen Ke wettable powder 1000-fold solution or 80% wettable sulfur powder 400-fold solution, spraying once every 7 to 10 d; for ring spot, use 70% thiophanate-methyl wettable powder 1000-fold solution, spraying once a week for 3 consecutive times, and collect and burn the fallen leaves.
2 Insect pests There are mainly more than 20 kinds, including leaf mites, leafhoppers, scale insects, coffee wood borers and tussock moths. Common insect pests: (1) Leaf roller, can be sprayed with 5% Cascade emulsifiable concentrate 1500 to 2000-fold solution, 10% Cypermethrin emulsifiable concentrate 3000-fold solution, 90% crystalline trichlorfon 500 to 800-fold solution. (2) Tussock moth (caterpillar), can be sprayed with 80% dichlorvos 1000-fold solution or 2.5 deltamethrin emulsifiable concentrate 5000 to 1000-fold solution. (3) Scale insects, during the peak occurrence period of young larvae, spray with 40% Supracide emulsifiable concentrate 500 to 1000-fold solution, 50% malathion emulsifiable concentrate 800-fold solution, 40% omethoate emulsifiable concentrate 800-fold solution. (4) Leaf mites, spray with 25% phosmet and 20% dicofol each at 1000-fold solution.
In recent years, in order to reduce pesticide residues in the fruit, Taiwan Indian jujube cultivation has begun to adopt net-house cultivation, achieving good results. In net-house cultivation, except that diseases still require spraying, among insect pests only mites are seen, greatly saving the amount of pesticide and labor costs; and for the mites inside the net house, experiments were carried out releasing green lacewings for biological control, achieving initial success.
Production period regulation
The peak production period of Taiwan Indian jujube is from December to February, and the production period is too concentrated, causing the phenomenon of cheap fruit hurting farmers. Adjusting the production period to September to March can stagger fruit harvest by about 7 months before and after, so as to increase the income of fruit growers. The measures are as follows:
8.1 Use early-maturing or late-maturing varieties Such as the early-maturing varieties Lizai jujube, Telong, Roulong; and the late-maturing varieties Biyun, Hongyun, Jinche, Huangguan, etc. Telong and Roulong, because their fruit has no astringent taste, are the preferred varieties for production period regulation.
8.2 Use regional climate differences and renewal pruning to regulate the production period In the Dashe area, branches and small branches are removed in late January, or the main branches are kept at about 1m, and the early-maturing variety Lizai jujube is grafted in early to mid-February, which can advance the production period so that harvest begins in mid-September; in the Yanchao area, renewal pruning is carried out in mid-February, and mid- and late-maturing varieties are grafted from late February to early March, which can delay the production period so that harvest is completed by late March.
8.3 Night lighting to advance the production period The suitable period for lighting is 120 to 130 d after trunk renewal (about late June), based on the visible formation of flower buds with the naked eye. Set up 1 40w fluorescent lamp between every 2 plants at a position 1m above the canopy, with a continuous lighting time of 40 d; with 12 h of lighting per day, the fruit can mature 45 d earlier; with 9 h and 6 h of lighting, it can mature 40 h and 35 h earlier; the fruit quality of the lighting treatment is no different from that without lighting in the same period, and the yield can also be increased.
Other points to note
1 It is advisable to build the orchard in a sheltered place. In areas with relatively severe wind injury, windbreak facilities are needed, such as planting windbreak forests, which can increase the fruit-setting rate.
2 Pollinizer trees should be arranged in the orchard, and their compatibility with each other should be high, such as interplanting Biyun with Thai honey jujube, and interplanting Roulong with Biyun, etc.
3 Because the current-year branches and shoots of the Indian jujube are soft in wood and cannot bear the weight of the fruit, after a heavy fruit set, the fruit and branches often hang down to the ground or the branches and shoots break, so supports must be set up in time to fix them. The Indian jujube is a shallow-rooted fruit tree, and in addition the flowering season often encounters typhoon strikes, so setting up supports is very important.
4 The Indian jujube should keep the soil dry and must not be irrigated in the month before the flowering period and during the young fruit period; only when the young fruit reaches 1.5 cm in diameter should irrigation begin to keep the soil moist, and at other times the orchard soil should also be kept moist regularly.
5 Because the Indian jujube has a large fruit set, young fruit should be thinned in time in production, removing diseased, pest-damaged and deformed fruit, etc., and it is suitable to keep one fruit per node on a fruiting branch; in addition, all fruit set after Frost's Descent should be thinned to avoid consuming nutrients and affecting the earlier fruit growth.
6 The Indian jujube is prone to bud mutation and natural hybridization, thereby producing new varieties, so each year attention should be paid to planting superior ones and selecting for grafting, so as to eliminate old varieties.