Key Technical Points and Management Methods for Winter Jujube Cultivation

Winter jujube (also known as Yanlaihong, apple jujube, rock sugar jujube, Huanghua winter jujube, Miaoshang winter jujube, Zhanhua winter jujube) is a high-quality late-maturing fresh-eating variety from the northern Shandong region. Winter jujube belongs to the Rhamnaceae family, genus Ziziphus. It is an excellent late-maturing fresh-eating variety of the thornless jujube tree. It is distributed in Shanxi, Hebei, Shandong and other places. Winter jujube generally ripens naturally between October and November on the Gregorian calendar, and because the weather in the north turns cold relatively early, it is named "winter jujube".

I. When Is the Best Time to Plant Winter Jujube

In the main winter jujube production areas of the north, planting with leaves in late September is best. This time is the early stage of jujube fruit harvesting, and the warm and humid conditions are beneficial to the rooting and growth of the seedlings. The soil is relatively warm and moist, the temperature gradually drops, the leaves of winter jujube seedlings begin to turn yellow, the nutrients in the plant begin to flow back to the roots, and the nutrient content and moisture content of the seedling trunk and roots are high. After planting, the relatively high soil temperature and relatively moist soil are conducive to root development before winter.

II. Winter Jujube Tree Cultivation Techniques

1. Site selection and orchard establishment: When establishing an orchard, choose high-quality virus-free seedlings that are robust, have well-developed root systems and are free from pests and diseases. The orchard site should preferably have fresh air, clean water, uncontaminated soil, flat terrain, open topography, sufficient sunlight, fertile soil, good drainage and irrigation conditions, soil free of harmful and toxic substances, soil minerals within the normal range, and no pesticide residues or contaminated plots.

2. Timely planting: Winter jujube has strong adaptability and tolerates drought and poor soil, and does not have strict requirements for fertilizer and water. Dense dwarf cultivation should be adopted when establishing the orchard, generally 2 to 3 x 3 to 4 m, with 56 to 111 plants per mu, which has an obvious effect on increasing the early yield of young trees. Winter jujube has relatively high light requirements, so the row direction should preferably be north-south.

3. Fertilizer and water management: Winter jujube has a relatively high demand for phosphate fertilizer. When planting, apply 0.5 kg of superphosphate and 25 kg of organic fertilizer per plant. Apply chemical fertilizer once each year in late May, late June to early July, and early August. In autumn, apply organic fertilizer in trenches, with 50 to 70 kg of farmyard manure and 0.5 to 1 kg of nitrogen and phosphate fertilizer or the same amount of three-element compound fertilizer per plant. Irrigate thoroughly once each before jujube trees sprout, before flowering, during the young fruit expansion stage and before overwintering. At other times, irrigate appropriately according to drought conditions, drain promptly during the rainy season, and cultivate and weed promptly after rain. Plow and turn the tree in autumn.

4. Flower and fruit management: First, pinch off the growing tips of jujube heads at the early full-bloom stage, leaving 3 to 5 secondary branches for pinching according to the vigor of growth. Second, spray clean water from the early flowering stage to the full-bloom stage once every 1 to 3 days for a total of 3 to 5 sprays. Third, hormone treatment: spray 1 to 2 times with 10 to 15 mg/L gibberellin at the early full-bloom stage. Fourth, girdling and ring cutting: for young vigorous trees, perform trunk ring cutting at the full-bloom stage, and when the trunk diameter reaches more than 5 cm, perform girdling with a width of 0.5 to 1 cm. For large trees in the fruiting stage, girdling can be done on the trunk, while young trees just beginning to bear fruit are generally girdled on the main branches, so as to achieve both fruiting and tree maintenance without compromising either. The cut is best healed in about 20 days, so as to achieve the purpose of intercepting nutrients on the tree to preserve fruit.

5. Training and pruning: The tree shape of winter jujube depends on planting density. For 55-100 plants per mu, a small canopy and open-layer shape should be adopted to maintain ventilation and light penetration. The trunk-setting height at planting is 70 to 80 cm, and 5 to 6 main branches are gradually developed year by year. During winter pruning and summer pruning, water sprouts should be removed promptly, extension branches should be shortened, and excessively dense and weak branches should be thinned and cut back, so as to maintain tree vigor balance, keep the canopy ventilated and light-transmitting, and promptly retract excessively long fruiting branches. This allows local branches to be renewed and rejuvenated.

6. Disease and pest control: The main diseases and pests of jujube trees include spider mites, peach fruit moth, jujube looper, jujube rust, jujube fruit-shrinking disease, jujube witches' broom, etc. During the bud break and leaf expansion stage, spray 40% omethoate emulsifiable concentrate at 1000 times 1 to 2 times to control jujube looper. From late May to early June during the spider mite occurrence period, spray 15% saomanting emulsifiable concentrate at 2500 times 1 to 2 times. From mid-July to mid-August, spray pyrethroid pesticides 2 to 3 times to control peach fruit moth and jujube looper. In July, August and September, spray fungicide once every 15 to 20 days. A 200-fold Bordeaux mixture can be used alternately with 800-fold carbendazim solution or 1000-fold thiophanate-methyl wettable powder to control jujube rust and fruit-shrinking disease. If jujube witches' broom is found, prune out diseased branches in mild cases and remove them promptly in severe cases.

7. Harvest and storage: Winter jujube is a fresh-eating variety and is mostly picked by hand. Winter jujubes on the same tree have different ripening periods, so they can be harvested 2 to 3 times according to the situation. Harvesting in stages can not only increase yield but also improve quality. After harvest, they are generally stored fresh in cold storage, and low-temperature conditions can inhibit the production of ethylene in winter jujubes. The storage temperature in cold storage is best at about 1°C, and the relative humidity should be maintained at about 98%, to supply the market around New Year's Day and the Spring Festival.