Key Cultivation Techniques for High and Stable Yield of Feizixiao Lychee

Feizixiao lychee is an excellent mid-to-early maturing variety from Guangdong, with large fruit, thick flesh, attractive color, small seeds and sweet taste, and excellent quality and flavor; its best eating period is when the peel is green with a red tinge. Feizixiao has strong adaptability to climate and environment, vigorous vegetative growth, and flowers easily, but it has a large number of flowers, an early flowering period, and difficult fruit set.

The focus is on using physical and chemical regulation techniques on Feizixiao flower panicles to improve fruit set, and by taking advantage of its vigorous growth and strong response to pruning, appropriately increasing planting density so that it bears early, yields high and yields stably, making it a fast-developing excellent variety.

1 Reasonable close planting to increase yield per unit area

Close planting and dwarfing cultivation have long been an important technical reform in modern fruit tree production, as it helps change extensive cultivation into intensive management and achieve the goals of early bearing, high yield and high efficiency in fruit trees.

Feizixiao plants grow vigorously, their crowns grow quickly, they respond strongly to pruning, and their new shoots have a high heading rate, which is favorable for retractive pruning after close planting. Through retractive pruning, Feizixiao can absolutely be grown with close planting and dwarfing, and achieve high and stable yield; the yield per mu once reached 2600 kg, equivalent to 10 times the average yield per mu of bearing trees in the province. Generally, planting density is determined according to cultivation conditions, technology, area and investment capacity. For large-scale planting, 35-50 plants per mu can be used; for small-scale planting, 75 plants per mu; and where water and fertilizer conditions, cultivation techniques and investment conditions are especially good, a planting density of 100 plants per mu can be used.

2 Cultivating a crown for early bearing and high yield

To achieve early bearing and high yield, Feizixiao needs a round-headed crown with evenly distributed branches, good ventilation and light penetration, and strong shoots that can bear future heavy yields. Feizixiao has thick branches and large leaves, vigorous tree vigor and obvious apical dominance; when fertilizer and water conditions are good, branches and leaves grow excessively and the crown becomes sparse. On the basis of improving soil fertility, young Feizixiao trees can be encouraged to flush more than 5 times per year. Leave 3-4 new shoots at the 40-50 cm part of the trunk as main branches; when the main branches grow to about 30 cm, pinch or cut back the tips, leaving 1-2 as side branches; afterward, when the second and third order branches grow to 30 cm, continue pinching to promote branching, leaving 1-2 new shoots per branching and pruning off the rest. Starting from young trees, a crown for three-dimensional fruiting should be cultivated; during pruning, frequent pinching and cutting back should be used to increase branch density, while overly thin branches and shaded branches should be cut off, gradually training young trees into a round-headed high-yielding crown. When tree height and crown width reach more than 1.5 m and there are more than 30 bearing mother branches, measures can then be taken to bring young trees into the bearing period.

Under day and night temperatures of 20°C and 15°C respectively, Feizixiao can show flower bud differentiation after 40-56 days. Therefore, the generally low-temperature and dry winter conditions in Guangdong easily satisfy the flower bud differentiation conditions of Feizixiao, so seedlings and young trees easily flower and fruit, consuming large amounts of nutrients from the tree body, making shoot flushing difficult for young trees; the shoots produced are numerous but weak, affecting crown expansion. An effective measure to prevent flowering of Feizixiao seedlings and young trees is, after the last autumn shoot matures, that is, starting in mid-October, to apply fertilizer water once every two weeks for 3 consecutive times, which can promote winter shoot growth, inhibit flower bud differentiation, prevent flowering the following year, and accelerate crown formation. If young trees flower, the flower panicles are generally cut off in mid-to-late March.

3 Cultivating good bearing mother branches

Bearing mother branches store large amounts of nutrients for consumption during flowering and fruit set, and are the basic condition determining yield level. There are mainly two criteria for evaluating excellent bearing mother branches (that is, the last autumn shoot after harvest): first, the autumn shoot flushes at the right time; second, the autumn shoot is robust. In Guangzhou, after Feizixiao fruit harvest, the first shoot usually sprouts in early-to-mid July, the second in early-to-mid August, and the third autumn shoot (the last shoot) sprouts from late September to early October. After harvest, by controlling fertilizer and water, pruning and bud removal, two rounds of shoots can be cultivated, which can meet the needs of the next year's production while preventing premature crowding between plants. In the Guangzhou area, the maturation period of Feizixiao bearing mother branches is generally in early November, and mid-November is the starting period of flower bud differentiation in Feizixiao. The criteria for robust Feizixiao autumn shoots are freedom from pests and diseases, thick branches, dark green leaves, thick leaves with a hard feel, and by December to January of the following year, the middle part of the bearing mother branch reaches 0.5-0.6 cm in diameter and 30-40 cm in length, with 70-80 leaflets.

4 Cultivating flower panicles with a high fruit-setting rate

Feizixiao flower panicles are especially large, with many flowers and an early flowering period. Generally, without treatment, under artificial pollination conditions, the fruit-setting rate of Feizixiao flower panicles is only 3.6%, so its fruit set is very poor. After the flower panicles are treated, short and sturdy flower panicles are cultivated, the floral organs develop soundly, and flowering is delayed, the number of flowers is reduced, the proportion of female-fertile flowers is high, the opening period is long, and the meeting time of female and male flowers is long, thereby increasing the fruit-setting rate. The following measures can be used to improve flower panicle quality.

4.1 “One removal, two thinning, three cutting back”

4.2 Using spiral girdling technology

4.3 Chemical control of panicles

4.4 Measures to keep flower panicles green

5 Improving fruit quality and yield

Feizixiao is mainly an aborted-seed variety, and there may be fruit drop caused by root and shoot growth during fruit set, similar to young Nuomici. Therefore, in order to stabilize Feizixiao fruit set, it is necessary to girdle once on the main branch or large branch at the end of April to reduce fruit drop, or use spiral girdling to promote flowering and preserve fruit.

According to research, the eating quality of Feizixiao is best when the fruit is 80% mature (that is, when the peel is green with a red tinge). At this time, the acid content and vitamin C content of the flesh are both relatively high, the sugar-acid balance is moderate, and it has a special aroma, making it the best time for fresh eating. When harvested when the peel is fully red, the acid content and vitamin C content both decrease, and eating quality declines. Therefore, the best harvest period for Feizixiao is when the fruit is green with a red tinge and shows a “jade lotus bud” shape.