What to Do About Low Yields of Apple Trees on Barren, Dry Hillsides? A Detailed Guide to High-Quality, High-Yield Cultivation Techniques

To promote the development of the fruit industry in Chengde, increase fruit yield and quality, and accelerate the pace of development of the economic forest industry, starting in 2014 the Chengde Municipal Forestry Technology Extension Station carried out the construction of a demonstration base for quality improvement and efficiency enhancement of low-yield apple orchards in Kuancheng County, and achieved good results. The techniques are summarized below for reference.

1. Top grafting for variety improvement.

① Main varieties: 8 apple varieties suitable for high quality and high yield were promoted, including Hanfu, Yueyanghong, Yueguan, Yuehua, Yueyan, Meiguo No. 8, Red General and Changfu No. 2.

② Grafting time and methods: Before grafting, strengthen fertilizer and water management to restore tree vigor. Spring grafting methods include cut grafting, cleft grafting, bark grafting and side grafting. The method used is chosen according to the thickness of the grafting site: for thin branches, use cut grafting or cleft grafting; for thick branches, use cleft grafting, bark grafting, etc.; for parts of the trunk or main branches lacking branches, use side grafting. Use wax-sealed scions, and the cut surface should be flat and relatively long. After inserting the scion, bind the wound with plastic strips.

③ Tree shape renovation: For densely planted trees, renovate the tree shape to a modified spindle shape or free spindle shape; for medium-canopy trees, use a trunk-based delayed open-center shape and other tree shapes. First select the skeletal branches. For main branches with a base diameter within 3 cm, leave about 10 cm and perform bark grafting, generally inserting 2 scions; for those with a diameter over 3 cm, starting 30 cm from the base of the main branch, select the branch axes of small branch groups on both sides of the main branch for side grafting, with a spacing of 30-40 cm on one side; for bare, branchless areas too far away to graft, use side grafting to fill them in.

2. Soil, fertilizer and water management.

① Soil management: The deep plowing time is from after fruit harvest in autumn to before leaf fall, with a depth of 30-40 cm. The deep plowing position is bounded by the outer edge of the tree canopy projection, and the inner canopy is shallowly cultivated. Deep plowing is carried out together with the application of organic fertilizer. Cultivate to remove weeds, and implement orchard mulching, spreading 1000-1500 kg of straw and weeds per mu, with a thickness of no less than 20 cm.

② Water management: In combination with water-collection facilities, water well at key times such as the pre-flowering water (from bud break to before flowering), post-flowering water (5-10 days after petal fall) and the freeze-up water. When the soil reaches field maximum water-holding capacity, drain promptly.

③ Increase organic fertilizer application: Fertilization is mainly based on autumn application of base fertilizer, supplemented by summer topdressing. Organic fertilizer is applied after fruit harvest, applying 1-2 kg of organic fertilizer for every 1 kg of fruit produced, mixed with an appropriate amount of calcium-magnesium phosphate fertilizer, at 150-200 kg per mu. For topdressing during the growing season: at the bud-break stage of the fruit tree, mainly nitrogen fertilizer; at the flower bud differentiation and fruit enlargement stages, use nitrogen, phosphorus and potassium in combination; at the late fruit growth stage, mainly phosphorus and potassium, to help coloring and increase nutrient reserves.

3. Flower and fruit stage management.

① Flower and fruit thinning: After flower buds swell, do a good pre-flowering follow-up pruning to maintain a flower bud to leaf bud ratio of 1:4-5. Thin fruit about 10 days after flowering, completing it within 3 weeks. Use the spacing fruit-setting method, selecting and keeping one central fruit with a regular shape on a robust fruit spur at 20-25 cm intervals, with a fruit retention of 10,000-12,000 per mu, and removing all excess young fruits.

② Fruit bagging: 1-2 days before bagging, use insecticides (acaricides) + fungicides (protective fungicides + therapeutic fungicides) + high-quality calcium fertilizer + agricultural water quality improver to control pests and diseases. When bagging, red varieties such as Red Fuji should use high-quality two-layer three-color paper bags, starting bagging 45 days after petal fall.

③ Laying reflective film: In mid-to-late August, lay silver-gray reflective film under the tree canopy.

④ Leaf removal and fruit turning: During the fruit coloring period, remove leaves that shade the apple fruits so that the fruits receive direct sunlight.

4. Key pruning techniques.

① Winter pruning: First, remove overly dense branches, upright competitive branches and diseased or pest-infested branches, adjust the opening angle and orientation of main branches, and adjust the tree structure from the overall perspective; second, retract branches that have not been pruned for many years and whose fruiting has shifted outward; third, adjust the internal structure, removing strong branches on the upper side and overly dense, thin and weak branches, crossing and overlapping branches on the lower side, and controlling competitive branches; use auxiliary nurturing branches, select and cultivate small and medium-sized fruiting branch groups, and for some spaces, cut back the base of current-year branches at 3-4 buds to stimulate the germination of sub-full buds and cultivate them into compact small and medium-sized fruiting branch groups.

② Summer pruning: The main pruning methods are propping, pulling, levering, bending, pressing, pinching and twisting shoots. For main branches with unreasonable opening angles, use propping, pulling and other methods to open the angle to 70-80°; for main branches and side branches with unreasonable angles, use bending, oblique pulling and other methods to change direction.

5. Pest and disease control.

Adhere to the strategy of "prevention first, integrated control", promote the use of low-toxicity, residue-free pesticides and biological pesticides, and produce green, pollution-free fruit. After winter pruning, spray 5 degrees Baumé lime sulfur to prevent rot disease, scale insects, rust disease, dry rot disease, etc. In April, use insecticides such as avermectin-type and imidacloprid to control aphids, fruit borers, inchworms, etc., and spray triadimefon, kejunling or carbendazim to prevent rust disease and powdery mildew. From late June to August, use insecticides such as avermectin-type and pyrethroid-type to control pests such as scarab beetles, longhorn beetles, psyllids and slug moths. After July, spray Bordeaux mixture 4-5 times to prevent apple sooty blotch.

Chengde Municipal Forestry Technology Extension Station: Gao Jianli, Jin Tiejuan, Geng Jinchuan