Detailed Explanation of Key Techniques for Flower and Fruit Retention in Navel Oranges
The ultimate purpose of growing navel oranges is to obtain a good return, and the yield of navel oranges is, apart from the price factor, the hard guarantee for obtaining benefits. To achieve high yield, besides reasonable cultivation and planting and a suitable growing environment and climate, the number of flowers and fruits is a foundation.
Flower and Fruit Retention Techniques for Navel Oranges
1. Timely pruning and bud removal
After navel oranges bud in spring, they should be thinned and pruned in time, cutting off the terminal winter shoots, water sprouts, diseased and pest-infested branches, weak branches, and excessively dense branches on the outer canopy, and removing leafless spherical flowers and deformed flowers. Shorten overlong autumn shoots, leaving 3-6 flowers, and follow the method of “remove three, keep one; keep two out of five” to retain the strong and remove the weak. Cut off clustered branches, remove strong spring vegetative shoots at the top and periphery of the canopy and excessively dense short weak spring shoots; for overlong spring shoots, retain only 5-7 leaves for pinching or short cutting, and thoroughly remove late spring shoots, summer shoots and early autumn shoots.
2. Flower and fruit retention
Spray once each at the bud stage, petal-fall stage and young fruit stage with 0.3% urea + 0.3% monopotassium phosphate + 0.2% borax (or boric acid). When 2/3 of the petals have fallen and after the first physiological fruit drop (early to mid-May) and before the second physiological fruit drop (early June), spray once each with 50 ppm “920” + 0.3% imported compound fertilizer (spray only on flowers and young fruits). In late May, apply a mixture of 250 ppm “920” + 0.3% monopotassium phosphate + 0.3% urea to the young fruits.
3. Preventing navel yellow fruit drop
When 4/5 of the petals of navel oranges have fallen, combine with flower and fruit retention spraying of 70% thiophanate-methyl 800-fold solution + 50 ppm “920”. From late April to early May, spray the canopy with 300-fold amino acid compound fertilizer or 800-fold Greenfenwei No. 2 and other foliar fertilizers. In early June (after the second physiological fruit drop), spray the canopy with 50 ppm “920” + 0.4% imported compound fertilizer + 70% thiophanate-methyl 800-fold solution. Or apply 200-300 ppm “920” + 70% thiophanate-methyl 800-fold solution to the navel, and spray (or apply) again after an interval of 10-15 days. From late July to mid-August, apply 600-800 fold “Yellow Inhibiting Ester” to the navel to inhibit the occurrence of navel yellow.
4. Preventing fruit cracking and fruit drop caused by cracking
In dry seasons, irrigate in time and mulch the tree disc, with a grass cover thickness of 10-15 cm. Before mulching, carry out shallow intertillage and loosening of the soil around the tree disc, and spray 0.3% monopotassium phosphate at the young fruit stage. From June to August, especially in early to mid-July, apply 1-2 additional potassium fertilizer applications; respectively from early to late June after the second physiological fruit drop, use 200-250 ppm “920” to dab the navel of young fruits (for fruits with slight initial cracking, 800-fold 70% thiophanate-methyl can be added to the “920”), and in July-August during fruit expansion, continuously spray 2-3 foliar fertilizers, which may be 800-fold Greenfenwei No. 1; or PBO 300-500 fold; or 0.3% potassium sulfate compound fertilizer; or spray a mixture of 0.3% urea + 0.2% monopotassium phosphate + 0.1% quicklime + 0.1% table salt for better results.
Site Selection and Orchard Establishment for Navel Orange Planting
Generally, a mountain site with sufficient water sources, convenient transportation, facing south with its back to the north, deep soil layers, and fertile and loose soil can be chosen for orchard establishment. When establishing an orchard on sloping land, terraces should be well built, generally with a belt width of more than 2.5 m, and planting holes 1 m in length, width and height, or trenches 80 cm deep and 1 m wide can be dug for planting. The planting specification for navel oranges is row spacing 1 m × 1.5-2 m plant spacing, and the planting time is before spring shoot sprouting or after autumn shoots mature.
Harvesting of Navel Oranges
For navel orange fruits to be stored after harvest, it is generally best to pick them when 80% of the fruit surface is colored and the fruit has not yet softened. Within half a month before harvest, it is not suitable to apply chemical fertilizers or irrigate heavily; the best harvesting time is on sunny days; harvesters should trim their nails flat, because the quality of harvesting technique directly affects the storability of navel orange fruits, and bruise-free harvesting is the key to reducing diseases during fruit storage. Use the two-cut method for harvesting: the first cut should be made 1 cm from the fruit stem, and the second cut should be flush with the fruit stem. When harvesting, work from the outside to the inside and from top to bottom, and during harvesting, handle gently, pack gently, load and unload gently. At the same time, diseased and pest-infested fruits, cracked fruits and deformed fruits should be removed to avoid mixed packing.
Storage of Navel Oranges
1. Ordinary warehouse storage: In the initial stage after the fruits are put into storage, the temperature inside the warehouse is high and the humidity is high, so doors and windows should be opened all day for ventilation and air exchange to lower temperature and humidity; in low-temperature weather, open windows during the day to increase temperature and close them at night to keep warm. To reduce fruit moisture evaporation, in the middle and late storage periods, cover the fruit boxes with a layer of plastic film; when water droplets appear on the fruit peel or the film, uncover the film and cover again after it dries. After the fruits are put into storage, check once every 10-15 days, and pick out damaged, rotten and diseased fruits. After the Beginning of Spring, select fruits once every 5-10 days.
2. Plastic film tent storage: The main point is to check frequently; when water droplets condense on the tent wall, open the tent for ventilation to avoid deterioration and rotting of navel oranges. Check and select fruits once every 10-15 days, and pick out damaged, rotten and diseased fruits.
3. Ground cellar storage: After the fruits are put into the cellar, check once every 7-10 days, mainly to check the condition of rotten fruits and exchange fresh air, and promptly lower temperature and humidity. In the early stage, water vapor also needs to be removed. When checking for rotten fruits, the personnel should first blow air into the cellar before entering to drive out carbon dioxide, and then enter the cellar. To remove water vapor, hang a bundle of ten straws in the cellar, and after the straws absorb enough water vapor and become wet, replace them with a dry bundle of straw. With this kind of ground cellar storage, navel oranges can be stored for 6 months, and the good fruit rate can reach about 90%.
According to some of the flower and fruit retention techniques and methods described in this article, under conditions without special or major natural disasters, the number of navel oranges can be guaranteed. But to obtain better returns, besides quantity, quality is another important indicator.