Key points of early high-yield cultivation techniques for pear trees
1. Large holes and deep planting
From April 5 to 10, select healthy, pest-free one-year-old seedlings with a diameter of more than 1.0 cm at 2 cm above the graft union and a height of more than 1.5 m. Before planting, cut off damaged roots and overly long roots, soak them in clean water overnight, and the next day dip the seedlings in mud slurry before planting. The planting hole should be 1 m long, 1 m wide, and 1 m deep. Keep topsoil and subsoil separate, water thoroughly, and plant after the water has completely infiltrated.
Plant about 5 cm deeper than normal tree planting. Use only topsoil for backfilling; where conditions permit, replace the soil or mix in an appropriate amount of organic fertilizer. When filling soil, lift the trunk gently, firm it down, and then water thoroughly again. After the water infiltrates, mound a small pile of soil at the base of the tree to reduce water evaporation and improve the survival rate. A survey three weeks after planting showed a survival rate of 99.6%.
2. Training and pruning
Use a two-main-branch open-center form to increase early canopy coverage as quickly as possible and reduce soil moisture evaporation. Use the bending-trunk method during training. After planting, bend the trunk about 65 cm above the ground toward the east to about 75° and train it as the first main branch. When an upright shoot emerges near the bend, select and keep one to train as a vigorous branch. In the second spring, bend the branch from its base toward the west to about 75° and train it as the second main branch. If sprouting is delayed after the trunk is bent down, about 15 d after bending, apply a bud-breaking compound (produced by Handan Northern Biological Products Co., Ltd.) to the buds or use measures such as notch budding to promote sprouting. The two main branches should preferably be spaced 10-15 cm apart to prevent splitting.
Do not keep lateral branches on the main branches; have fruit-bearing branch groups directly on them. During winter pruning, mainly thin out; do not cut back the tips of the main branches, so as to suppress the front and promote the rear, allowing large numbers of fruit-bearing branch groups to form early at the base of the main branches. After the canopy closes, use a downward-facing branch to replace the tip of the main branch to prevent overlap. Branch groups are pruned by the “three sets of branches” method, that is, current-year fruiting branches, fruit-bearing mother branches, and vegetative branches each account for 1/3. The horizontal distribution of branch groups on the main branches is “small on top, large below, medium on the sides,” that is, small branch groups (less than 20 cm long) are borne on the upper side, large branch groups (about 40 cm long) on the lower side, and medium branch groups (about 30 cm long) on both sides. The vertical distribution is large branch groups at the base, medium branch groups in the middle, and small branch groups at the top. The whole tree has about 30 branch groups of various types.
3. Growing grass mulch and fertilizer-water management
Select and keep 1-2 species of grass suitable for the local ecological conditions, such as crabgrass, as orchard ground cover. When the grass grows to about 25 cm, mow it, and after mowing spread the grass evenly over the ground surface. Repeat this process, mowing 2-3 times each year. This can reduce direct sunlight on the ground, lower surface temperature, and reduce soil moisture evaporation; after the weeds rot, plow them into the soil to increase soil organic matter. Using this method, over three years the soil organic matter in the 0-40 cm layer increased from the original 0.21% to 0.84%. Organic fertilizer is applied mainly as weeds, combined with an appropriate amount of farmyard manure, between summer and autumn. Do not trench and fertilize in spring, so as to avoid large losses of soil moisture. Apply urea 7 d before flowering: 100 g per tree for 2-year-old trees, 150 g for 3-year-old trees, and 200 g for trees 4 years and older. During the rapid expansion stage of young fruit, apply diammonium phosphate: 100 g per tree for 3-year-old trees, 150 g for 4-year-old trees, and 200 g for trees 5 years and older. Irrigate promptly after fertilizing. After petal fall, spray a mixture of 0.5% urea + 0.3% potassium dihydrogen phosphate once every 15 d, for a total of 4-5 times.
4. Pest and disease control
The main insect pests include pear aphid, pear fruit borer, tent caterpillar, scarab beetle, and green slug caterpillar. Use pollution-free pesticides such as the diflubenzuron series and B.t. emulsion (Bacillus thuringiensis). Pay attention to protecting and using natural enemies, such as green lacewings, ladybugs, and robber flies. For pear fruit borer and pear small borer, in addition to chemical control, supplement with manual removal and destruction of infested fruit to reduce pest population density. During winter pruning, remove tent caterpillar egg masses, and manually destroy newly hatched larvae when they disperse to feed during the flowering period.
The main diseases include gray leaf spot and brown spot, with a small amount of scab occurring. Spray 5°Be lime sulfur mixture at spring bud break to reduce the pathogen base. During the rainy season, spray 50% carbendazim wettable powder at 800 times dilution twice to control disease occurrence and protect leaves and fruit.