Detailed Guide to Management Plan for Apple Trees in the Mid-to-Late Growth Stage

I. Soil, Fertilizer and Water Management

1. Soil management. Deep plowing and pressing in green manure. The depth of deep plowing is generally 20-80 cm. Sweet clover and shrubby false indigo are preferred for green manure, but local materials such as vitex twigs and other green plants can also be used as fertilizer sources.

2. Fertilization.

Topdressing: During the mid-to-late growth stage of apples, topdressing should focus on phosphorus and potassium fertilizers. Starting from mid-August, spray a 0.3%-0.5% potassium dihydrogen phosphate solution, once every half month, for 2-3 consecutive applications, to promote the cessation of shoot growth. From July to September, spray once monthly with a 300-500 times dilution of amino acid calcium or amino acid compound micro-element liquid fertilizer. From 4 weeks before harvest, spray amino acid calcium liquid fertilizer once weekly to prevent bitter pit. Spray rare earth once each at 40 days and 20 days before harvest. One month before harvest, spray photosynthetic micro-fertilizers, Nongjiawang, apple enlarging and coloring micro-fertilizers, etc., which can increase the soluble solids content of bagged fruit. Foliar topdressing should be done in the morning or evening, and the spray should mainly target the undersides of leaves. No foliar topdressing within 20 days before harvest. Foliar topdressing is generally combined with pesticide spraying.

Base fertilizer: Generally applied from late September to early October before or after fruit harvest, mainly organic fertilizer, with fully decomposed organic fertilizer applied to the soil all at once. For young trees and trees in the early fruiting stage, apply 20-30 kg of organic fertilizer plus 0.2 kg of diammonium phosphate per tree.

For trees in full fruiting stage, the fertilizer amount depends on yield. At a yield of about 1000 kg of fruit per mu, every 100 kg of fruit produced requires 100 kg of high-quality organic fertilizer. At the same time, add 1 kg of diammonium phosphate, 0.5 kg of urea, 1 kg of potassium sulfate, or 10 kg of plant ash to every 100 kg of base fertilizer. Apply mainly by ring trenching or radial trenching. The position of ring trench fertilization should be directly below the vertical projection of the canopy edge, with a trench depth of 40-50 cm and width of 40 cm; the length depends on the amount of fertilizer. Radial trenching involves digging 4 radial trenches under the canopy in 4 different directions from the inside outward. The trench shape is 20 cm deep and wide on the inner side, and about 50 cm deep and wide on the outer side. When deep fertilization has been generally carried out under the canopy, it can be changed to broadcast application over the whole orchard followed by tillage. Deep application and broadcast application should be alternated in different years.

3. Watering. Water timely according to the water requirement patterns of fruit trees and soil moisture conditions. Irrigate once each during the young fruit swelling stage, and after fruit harvest until just before the soil freezes. Irrigate thoroughly once 3-5 days before bag removal to meet the water needs of bagged fruit and prevent sunburn. The irrigation amount should be based on soaking through the root distribution layer of 40-60 cm, reaching 60%-70% of field maximum water-holding capacity.

II. Pest and Disease Control

After mid-July, rainfall gradually increases and various diseases increase. Attention must be paid to leaf protection. Fungicides with leaf-protecting and fruit-protecting effects should be sprayed as usual to prevent fungi from entering the bags with rainwater and causing damage. According to the occurrence of pests and diseases, select several high-quality fungicides and insecticides for rational mixed spraying to reduce the number of spray applications. During continuous cloudy days or excessive rain, promptly spray protective plus systemic agents, such as 800 times dilution of Daconil M-45 mixed with 800 times dilution of 50% carbendazim, alternating with 1:3:200 Bordeaux mixture. Immediately after bag removal, spray once with 600 times dilution of Pencozeb, 800 times dilution of 25% thiophanate-methyl, or 800 times dilution of Guofukang to control ring rot and fruit rot caused by latent fungi in the fruit. At the same time, spray 1-2 times with medicinal fertilizers that have a coloring effect, such as 300 times dilution of potassium dihydrogen phosphate solution, 800 times dilution of Shikanglu, Nongjiawang, etc. After harvest, promptly collect and burn the used waste paper bags to eliminate pest and disease sources lurking on the bags and reduce damage in the following year.

III. Bag Removal

1. Timing of bag removal. For yellow-green varieties with single-layer bags, the bags can be removed at harvest. For red varieties using single-layer bags, tear the bag open into an umbrella shape 30 days before harvest, covering the fruit to prevent direct sunlight on the fruit surface; after 7-10 days, remove the entire bag to prevent sunburn and accelerate coloring. For red varieties using double-layer bags with separated inner and outer layers, remove the outer bag first 30-40 days before fruit harvest, and after 4-5 sunny days, remove the inner bag. For double-layer bags with the outer and inner layers stuck together, first open the bag mouth for ventilation, and after 4-5 days, remove the whole bag. If bags are removed too early, the fruit surface color is dark and the smoothness is poor; if removed too late, the fruit surface color is pale and the color fades easily during storage.

2. Bag removal method. When removing double-layer bags, first tear off the outer bag along the bag cut line, and after 5-7 days remove the inner bag. When removing single-layer bags, first open the bottom of the bag for ventilation or tear the paper bag into long strips, and remove it after a few days. Never remove bags all at once, otherwise sunburn is very likely, especially on clear and windless days.

IV. Measures to Promote Fruit Coloring

1. Leaf removal. Use scissors to cut off the leaves, leaving only the petioles. Leaf removal is generally done in two rounds. The first round is in early September, removing only the leaves that directly affect the fruit surface. The second round is in early October, removing a large number of leaves, mainly removing leaves at the base of the fruit spur, and also appropriately removing leaves from the base to the middle of new shoots near the fruit. When removing leaves, first remove yellow leaves, small leaves, and fallen leaves, then remove autumn shoot leaves. After leaf removal, more than 60% of the fruit surface should receive direct light, and the amount of leaves removed should account for 20%-30% of the total on the tree. When removing leaves, they must be removed in stages; do not remove too many at one time, to avoid sunburn on the fruit surface.

2. Fruit turning. Fruit turning is carried out about 15 days after bag removal, using methods that change the branch position and fruit orientation to turn the shaded side of the fruit toward the sunny side. To prevent the fruit from turning back to its original position, fix the fruit with transparent white tape so that it receives sufficient light. Fruit turning is done 2-3 times depending on the situation. Fruit turning should be done before 10 a.m. and after 4 p.m. to prevent sunburn.