When to Plant Nectarines in Greenhouses? Detailed Explanation of Key Cultivation Techniques
Nectarine is a type of peach with smooth, hairless skin, a sweet-and-sour flavor, and very crisp flesh; it is much smaller than ordinary peaches. Although its sales volume cannot match that of other peaches, it is indeed a variety with very high nutritional value. In recent years, to increase nectarine yields, many places have taken up greenhouse cultivation. When are nectarines in greenhouses generally planted? Which cultivation techniques need to be mastered?
1. How is the greenhouse built and the site selected?
The greenhouse site should be chosen in a place that is sheltered from the wind and faces the sun, with good drainage and irrigation, fertile soil, and sandy loam texture. It is a simple solar greenhouse, oriented east-west, with a north-south span of about 10 m and a length of about 60 m. The back wall and the walls on both sides are brick-concrete structures, 50 cm thick; the back wall is 2.5 m high, the ridge is 3 m high, and the ridge is 1.5 m from the back wall. The supports are reinforced concrete columns, and the frame material is bamboo and wood. Each side wall has one ventilation window, and the back wall has one ventilation window every 3 m. The greenhouse film uses polyvinyl chloride non-drip film with good light transmission and low water condensation, with the films pressed over each other, and hand-pulled straw felt covering the film. Once the nectarine's chilling requirement is met, dormancy can be broken and the temperature raised. The greenhouse is covered in early December each year; generally the straw felt is uncovered at 8:00 in the morning to improve the light conditions inside the greenhouse and raise the tree's nutritional level; at 16:00 in the afternoon the greenhouse is closed to maintain the temperature inside.
2. When is it planted?
The main cultivar grown in the Hefei area is Yanguang. Planting is from January to April. To make full use of the greenhouse's land area and increase yield per unit area, high-density planting is used, with a plant spacing of 1 m and a row spacing of 1.5 m. Dig planting trenches 70 cm wide and 70 cm deep, placing topsoil and subsoil separately, and apply 60 t/hm2 of high-quality decomposed organic fertilizer, 1800 kg/hm2 of superphosphate, and 7500 kg/hm2 of potassium sulfate. Fill the bottom of the trench with topsoil, mix the subsoil thoroughly with the fertilizer and fill it into the planting trench, water to settle it, then transplant; after planting, cover with soil and water, and fill the trench with soil to form ridges.
3. How is the temperature inside the greenhouse controlled?
Controlling the temperature and humidity inside the greenhouse well is the key link to increasing the fruit-setting rate and achieving early, high, and high-quality yields. The temperature inside the greenhouse is mainly regulated through ventilation windows and openings and by uncovering and covering the straw felt. Within 5 days of covering the greenhouse, first roll up half of the straw felt during the day to let in a small amount of light and gradually raise the temperature, which is beneficial for the peach trees' slow activity and the balanced metabolism of tree hormones and nutrients. After 5 days, roll up all the straw felt; the daytime temperature should be controlled at around 15°C, and at night it must not be lower than 5°C; during the budbreak period, maintain 15-20°C during the day, and at night it must not be lower than 5°C; during the flowering period, 15-20°C during the day, and at night it must not be lower than 8°C; during the young fruit swelling period, maintain 20-25°C during the day, and at night it must not be lower than 10°C; during the fruit coloring period, 20-25°C during the day, and around 5°C at night. Between the plants, dig hidden ditches 30 cm wide in the north-south direction, water them with hidden water, and cover the ditches with plastic film. This can reduce the humidity inside the greenhouse, increase light, and reduce the occurrence of pests and diseases. During the budbreak period, the relative air humidity should be kept at around 75%; during the flowering period, keep humidity at around 55%; during the young fruit period, keep it at around 65%.
4. The necessity of shaping and pruning
Use the open-center tree form. To enhance light, a trunk-training method of low in the south and high in the north can be used, with trunk-training heights of 20 cm, 30 cm, 40 cm, and 50 cm respectively. Each plant can have 3 robust main branches selected, with 3-4 side branches and 8-10 fruiting branches kept on the main branches; during the growing period, the canopy is controlled between 1.2-2.0 m, keeping the canopy 30-50 cm below the greenhouse film. During the budbreak period, promptly remove the buds below the trunk and the overly dense buds and upward-facing buds on the fruiting branches, and keep the side buds. Pull the main branches or side branches with a small opening angle to an angle of 45-70°. During the growing period, thin out overly dense branches, crossing branches, and conjoined branches, and cut back the stronger new shoots to promote the sprouting of secondary shoots, which are then selected and pinched to make the branches substantial and serve as fruiting branches for the following year. Winter pruning mainly removes overly dense branches, thin and weak branches, and upward-facing branches; for medium and long fruiting branches, prune lightly and keep more flower buds in the middle and upper parts for fruiting. It should be noted that high-density greenhouse nectarines often show the phenomenon of strong upper growth and weak lower growth; at this time, heavily prune the vigorous upper branches, remove the strong and keep the weak, to inhibit growth.
5. How are flowers and fruits managed?
During the growing period, spray 500-600 times diluted 15% paclobutrazol twice at 2-week intervals to control vigorous growth and promote canopy flower formation. Humidity inside the greenhouse is high, pollen does not disperse easily, and there are few pollinating insects; to increase the fruit-setting rate, artificial pollination is needed (generally smearing or releasing bees) or ventilation inside the greenhouse; spraying 0.3% borax + 0.3% urea solution at full bloom can increase the fruit-setting rate; during the flowering period, thin out conjoined flowers, thin and weak flowers, and deformed flowers; when thinning fruits, remove deformed fruits, small fruits, and diseased and insect-damaged fruits, and rationally retain fruits according to the load, keeping fruits with many leaves, side-borne fruits, and fruits on strong branches, and thinning out fruits with few leaves, lower-position fruits, upward-facing fruits, and fruits on weak branches. Flower and fruit thinning in greenhouse nectarines should be carried out on the principle of light flower thinning and heavy fruit thinning.
6. Soil, fertilizer, and water management
For spring topdressing, apply 0.3 kg of diammonium phosphate or compound fertilizer per plant before flowering and during the young fruit period; during the fruit swelling period, spray 0.3% urea and apply another 0.2 kg of potassium dihydrogen phosphate per plant. After harvesting the fruit, carry out deep plowing and fertilization to compensate for the nutrient consumption caused by the large fruit load. After the nectarine leaves fall and before the soil freezes, combine post-harvest pruning of the fruit trees with one trench fertilization. Dig trenches 40 cm wide and 40 cm deep between the rows, apply 75 t/hm2 of fully decomposed farmyard manure and 1800 kg/hm2 of three-element compound fertilizer, and irrigate thoroughly after fertilization. When digging the fertilization trenches, clean up the plastic film inside the greenhouse, then loosen the soil. The Hefei area has more rain in summer and autumn, so drainage and waterlogging prevention should be done promptly.
7. Pest and disease control
Pest and disease control adopts the principle of prevention first and comprehensive control. The main diseases are bacterial shot hole disease and gray mold, which can be controlled with fungicides such as chlorothalonil, 600-1000 times diluted 70% thiophanate-methyl, and mancozeb. The main pests include aphids and mites, which are controlled with 5°Bé lime sulfur mixture, fenpropathrin, and 2000 times diluted 20% clofentezine wettable powder. In winter, promptly remove fallen leaves, residual branches, and weeds, deep-plow the soil, and whitewash the tree trunks. It is worth noting that the temperature inside a greenhouse is greater than in the open air and air flow is small, so when applying pesticides the frequency should be increased and the dosage appropriately reduced to prevent pesticide damage.