Cultivation and Management Techniques for Young and Fruiting Lychee Trees
Lychee belongs to the Sapindaceae family and originated in our country. It is one of the four famous fruits of southern China, with a cultivation history of over 2,000 years. The following growth characteristics of young lychee trees have been summarized from lychee cultivation experience: (1) low branching order of shoots; (2) large shoot growth volume; (3) vigorous root growth; (4) early flowering period...
Lychee belongs to the Sapindaceae family and originated in our country. It is one of the four famous fruits of southern China, with a cultivation history of over 2,000 years. The following growth characteristics of young lychee trees have been summarized from lychee cultivation experience: (1) low branching order of shoots; (2) large shoot growth volume; (3) vigorous root growth; (4) early flowering period and low proportion of female flowers. The female flowering period is short, making fruit set difficult; (5) low nutrient accumulation level and strong sprouting ability of multiple buds. In response to the above five characteristics, attention should be paid to the following aspects in management, maximizing strengths and avoiding weaknesses, to achieve high and stable yields with bumper harvests every year.
I. Master Six Principles
1. In fertilization, reduce the proportion of nitrogen fertilizer, increase phosphorus and potassium fertilizer, supplement trace elements such as boron and magnesium, control excessive shoot growth, improve shoot quality, and make shoots robust, sufficient, and plump.
2. Cultivate two batches of autumn shoots, promote early maturation of the last autumn shoots, and accumulate sufficient flower bud differentiation substances (carbohydrates, proteins, and certain hormones).
3. After the last autumn shoots mature, control their growth, prevent winter shoot sprouting, allow leaf color to turn reddish, and promote flower bud differentiation.
4. Pre-flowering fertilizer, especially quick-acting nitrogen, generally should not be applied early; it is best applied after flower buds are visible.
5. Pruning should be light.
6. Pest and disease control should be timely.
II. Implement Four Measures
(1) Cultivate thick and strong superior fruiting mother branches
1. Timing and frequency of autumn shoot production: For two batches of shoots, the first is from late July to early August, and the second is from early September to early October. For a single batch of shoots, it is best to control it from late August to early September.
2. Apply shoot-promoting fertilizer well. This is the fertilizer applied before and after fruit harvest, mainly to rapidly restore tree vigor after fruiting and timely produce robust autumn shoots as fruiting mother branches. This fertilization is the key fertilizer for overcoming alternate bearing, mainly using quick-acting nitrogen fertilizer, generally accounting for more than 50% of the annual fertilization amount. For trees with very vigorous growth and few fruits, the amount should be appropriately reduced or this fertilization should be skipped to avoid winter shoot occurrence.
3. Pruning: For young trees, pruning should focus on the first 3 to 4 years; after 4 to 5 years, attention should be paid to retaining good secondary main branches and lateral branches. The pruning principle for young trees is light pruning. It should be carried out after the first autumn shoots mature and before the second autumn shoots sprout, removing diseased and pest-infested branches, overly dense branches, shaded branches, weak branches, overlapping branches, and dead branches. For 'Heiye' and 'Guiwei' varieties, shaded branches can also bear fruit, so more can be appropriately retained. It is advisable to retain about 40 last autumn shoots per square meter. For fruiting trees, pruning should be completed within one month after fruit harvest.
(2) Control growth and promote flower bud differentiation. Flower bud differentiation requires several specific prerequisites: first, timely production of good autumn shoots that are thick and robust; second, shoots must mature and accumulate sufficient flower bud differentiation substances without sprouting winter shoots; third, there must be 8 to 10 consecutive days of low temperatures of 0 to 10°C in winter. With the above prerequisites, combined with artificial physical and chemical auxiliary means, flower bud differentiation becomes more normal and reliable.
1. Control water and fertilizer, expand holes and cut roots, or deep hoe the tree disk to 15 to 20 cm, carried out after autumn shoots mature.
2. Ring cutting or ring girdling: For mid-to-late maturing varieties, flower bud differentiation occurs from November to February of the following year, with the peak period from December to the end of January. During this period, choose clear weather without north wind to make one ring cut or one spiral ring girdle, with a cut width of 2 mm.
3. After autumn shoots mature, spray Huaguoling 1 to 2 times, or from late November to December, continuously spray twice with 20 ml of 40% ethephon diluted in 20 kg of water plus B9, which helps inhibit winter shoot sprouting, promote flower bud differentiation, and increase the proportion of female flowers.
(3) Flower and fruit preservation
The type and amount of fertilizer and various artificial auxiliary means should be selected based on the interaction between vegetative growth and reproductive growth of lychee trees to achieve high yields.
1. Fertilization: Mainly organic fertilizer, supplemented by chemical fertilizer, with appropriate amounts of trace elements such as boron, magnesium, zinc, and molybdenum. It should be reasonable and moderate. Generally, for a tree producing 100 kg of fruit, the annual requirement is 3 to 4 kg of urea, 2 to 3 kg of potassium, 2 to 3 kg of phosphorus, and 2 to 3 kg of lime. Among these, shoot-promoting fertilizer is mainly nitrogen fertilizer with phosphorus and potassium combined. Flower-promoting fertilizer emphasizes N, K, and P equally, with an appropriate amount of lime. Fruit-preserving and fruit-strengthening fertilizer is mainly potassium, combined with N and P.
2. Release bees for pollination, or artificial supplementary pollination.
3. During high temperature and drought, water the trees and spray clean water in the morning.
4. Spray fruit-preserving agents. After 2/3 of flowers have fallen, spray Guoteling or "920", with each gram diluted in 30 to 35 kg of water, or one week before the second physiological fruit drop, carry out ring cutting for fruit preservation.
(4) Pest and disease control
Timely control of stink bugs, fruit borers, downy blight, and other pests and diseases.
1. Stink bugs, also known as stink bugs or stink pepper. Control methods for stink bugs are as follows: (1) During the period when winter temperatures drop significantly, especially when temperatures fall below 50°F, advantage can be taken of the adults' false death behavior by shaking the lychee branches, causing the adult stink bugs overwintering on leaves to be startled and fall to the ground, then sweeping and killing them. (2) Use 800 to 1,000 times dilution of trichlorfon, spraying once each before and after adult egg-laying and when larvae occur. The first spray is around early March, and the second around late April to early May. (3) In early spring, release Anastatus wasps (a type of artificially bred parasitic wasp) once, and release again in mid-May, using insects to control insects.
2. Control methods for fruit borers generally include two points: first, clear the orchard in winter, sweep away fallen leaves, fallen fruits, and weeds to eliminate overwintering pest sources; second, after full bloom, spray with trichlorfon diluted 1,000 times with water.
3. The pathogen of downy blight is a fungus. Control methods include the following three points: (1) Carry out summer orchard clearing to eliminate fungal sources; (2) In the early stage of fruit damage, spray 300 times dilution of 40% phosethyl-Al, or 800 times dilution of amobam, or 1,000 times dilution of metalaxyl; (3) In orchards that have been severely affected previously, during the flower bud stage and small fruit stage, spray once with 1,000 times dilution of ridomil or 1,000 times dilution of metalaxyl for prevention.