How to Plant Mountain Longan for Early Fruiting and High Yield

Longan is a subtropical fruit of high economic value and a specialty fruit tree of our country. In 1989, the longan planting area in Xinyi City was about 467 sq km, but due to extensive management, longan saplings grew slowly, came into production late, and even bore fruit only in alternate years, with low yields and poor returns, which dampened farmers' enthusiasm for planting. For this reason, starting in October 1991, we conducted a continuous 6-year early-fruiting and high-yield experiment at the Mountain Longan Farm of the Xinyi City Land Bureau. The trees began bearing fruit in the third year after planting, and the yield rose year by year, achieving good economic returns. Combining local conditions, we developed a set of early-fruiting and high-yield cultivation techniques for improved longan varieties suitable for mountain areas.

Management of young trees

The management of young longan trees mainly consists of agricultural measures such as soil improvement, fertilizer and water management, training and pruning, and pest and disease control, to rapidly form a high-yielding and stable-yielding framework and an irregular round-headed canopy, achieving the cultivation goals of early fruiting, high yield, stable yield, and high quality.

1. Deep plowing and green manuring to improve the soil

Based on the characteristic that young longan trees have a small root distribution range, measures such as expanding planting holes and burying green manure and intercropping crops are used to increase soil fertility and the ability to regulate water, fertilizer, air, and heat, improve the growing environment of the root system, and lay the foundation for high yield, stable yield, and high quality. Generally, from September to December, a trench is dug between 2 longan trees, with a trench width of 1-1.5 m and a depth of 0.7 m-1 m. After a period of time, green manure is buried in layers or farmyard manure is placed into the trench, and then lime is sprinkled on top.

2. Timely fertilization and timely drainage and irrigation

Young trees have smaller canopies and root systems, require little fertilizer, and their roots are sensitive to fertilizer, so the fertilization principle for young trees is frequent application of light doses. In the first year after planting, the first fertilizer is applied after the first flush of shoots matures, with 4-5 kg of manure water poured around each tree, or 15-25 jin of compound fertilizer diluted in water and poured on, after which it is applied 2-3 times each month. In the second year, the first fertilizer is applied around “Spring Equinox”, with 5-10 kg of composted and decomposed pig manure, 0.25 kg of peanut bran, and 0.25 kg of superphosphate per tree; the second and third applications are 0.25-0.5 kg of compound fertilizer per tree; and the fourth application is 5 kg of pig manure and 0.25 kg of peanut bran per tree. The first and second fertilizer applications after planting are applied 20 cm from the trunk, and thereafter applied in opposite-facing trenches under the canopy drip line, with a trench depth of 10-15 cm and a width of 20-25 cm.

For water management, attention should be paid to draining waterlogged water in the rainy season and watering to maintain moisture in the dry season.

3. Training, pruning, and shoot thinning

Training and pruning are aimed at cultivating a high-yielding and stable-yielding tree shape, so that branches are evenly distributed and develop in a balanced way. However, young trees generally do not need heavy pruning; the focus is on training to cultivate a high-yielding and stable-yielding canopy, concentrate nutrients for the growth of effective branches, promote the rapid formation of a round-headed canopy, and bring the fruiting stage forward.

① Bud retention: after the young tree survives, select and retain 2-3 new shoots with evenly distributed angles at 40-60 cm above the ground as main branches, and thereafter each time retain buds by removing the weak and keeping the strong, removing the inner and keeping the outer, and removing the lower and keeping the upper.

② Heading back: when the 2-3 main branches grow to 35 cm in length and more than 0.6 cm in thickness, head them back, leaving 25-30 cm at the base, and each subsequent heading back follows the same method.

③ Shoot thinning: after each heading back, when the new shoots are about 5-8 cm long, shoot thinning should be carried out. Generally, 2 new shoots are retained on each main branch (vigorous, with good branching angles), and then excess new shoots are wiped off.

Management of fruiting trees

When improved longan grafted seedlings are planted in mountain areas, under scientific management, in the third year after planting they have 4-6 levels of branching, more than 30 effective branches, and a canopy spread of more than 180 cm, and already have normal flowering and fruiting ability. After longan enters the fruiting stage, the canopy continues to expand, and each year deep plowing and green manuring are still needed, along with increased application of organic fertilizer, to mature the orchard soil. Deep plowing and soil improvement are carried out from December to January of the following year after the last flush of shoots matures, and can also play a role in controlling winter shoots and promoting flower bud formation.

1. Cultivating timely and vigorous fruiting mother branches

① Timely fertilization: the first fertilization is carried out 7-10 days before fruit harvest, the second after fruit harvest, and the third in October. The amount of fertilizer can be determined according to canopy size and fruit load. Taking a tree bearing 30 kg of fruit as an example, the first application is 1.5-2 kg of peanut bran (composted and decomposed) or 0-15 kg of chicken manure, and a small amount of chemical fertilizer can be added to the second and third applications. Fertilizer is applied in half-ring trenches under the canopy drip line, and soil is covered after application.

② Pruning and shoot thinning: pruning is carried out after the second fertilization and before the first flush of new shoots, mainly cutting off weak branches and diseased and pest-damaged branches, and heading back excessive vegetative branches. Shoot thinning is carried out when each new flush grows to 5-8 cm; for the first flush, only 2 new shoots are retained on each fruiting branch, and for the second flush, only 1 new shoot is retained on each fruiting branch, with the remaining buds removed. The retained new shoots should be vigorous and well angled, so that the developed fruiting mother branches reach more than 0.6 cm in stem thickness.

③ Shoot protection: during the growth of autumn shoots, they often suffer pest and disease damage. The main diseases are anthracnose and leaf spot. Anthracnose can be controlled with copper oxychloride at 600-800 times, and leaf spot can be controlled with thiophanate-methyl at 1000 times, following the practice of “two sprays per flush” to ensure vigorous shoot growth.

2. Winter control to promote flowering

Controlling the sprouting of winter shoots and promoting flower bud differentiation in longan is the key to flowering and fruiting the following year. The main measures for controlling shoots and promoting flowering in winter are as follows: ① Root cutting to suppress shoots and promote flowering. After the last flush of shoots fully matures, deeply hoe and turn the soil under the canopy drip line to cut some roots. ② Trunk girdling to suppress shoots and promote flowering. After the last flush fully matures, tie a ring of No. 14-16 iron wire tightly around the longan trunk, tight enough that it cannot move up or down, and remove the wire immediately after the leaf color returns to normal. ③ Application of chemical hormones. Spray leaves and shoots with 0.3%-0.4% paclobutrazol, or with special flower-promoting agents for lychee and longan such as Huaguoling.

3. Flower and fruit protection

① Fertilization

The first fertilization is arranged between “Start of Spring” and “Rain Water”, mainly with organic fertilizer plus an appropriate amount of potassium fertilizer, applied in opposite-facing half-moon-shaped trenches under the canopy drip line, with soil covered after application. The second fertilization is carried out in early May, mainly with compound fertilizer, broadcast under the canopy, followed immediately by loosening the soil. The amount of fertilizer depends on canopy size and tree vigor. Generally, for a tree bearing 15-20 kg of fruit, the first application is 5-10 kg of pig manure or chicken manure, 0.5-1 kg of peanut bran, and 0.5 kg of superphosphate, and the second application is 0.5-1 kg of compound fertilizer.

② Flower thinning

When the main axis of the flower cluster grows to 5-10 cm, pinch off the growing tip. Generally, 8-12 lateral flower branches are retained, and the length of the main axis and lateral flower branches is controlled to reduce the number of male flowers and increase the proportion of female flowers. At the same time, thin out slender and weak flowers and overly dense flowers to help increase the fruit-setting rate. The method of cutting the flower clusters can also be used. Generally, 1/3-1/2 of the flower clusters are cut off per tree, which not only ensures the current year's fruit load but also cultivates vigorous fruiting mother branches for the following year, reducing the phenomenon of alternate bearing and achieving the goal of high and stable yield.

③ Introducing bees for pollination

Placing 1 colony of honeybees per 0.2-0.3 sq km of orchard helps pollination and increases the fruit-setting rate.

④ Preventing flower soaking and flower burning

If longan encounters cloudy and rainy weather during the flowering period, the anthers are difficult to dehisce, and the phenomenon of rotten flowers, namely flower soaking, occurs. You can shake the branches at noon every day to shake off the rainwater on the flowers, let the flowers dry in the wind, and promote anther dehiscence, which is beneficial to pollination. If longan encounters continuous high-temperature weather during the flowering period, the stigmas of female flowers are easily burned, and because the nectar becomes concentrated and too thick, flower burning is likely to occur. You can spray water on the canopy every afternoon to dilute the nectar and increase humidity, preventing stigma burning and premature withering.

⑤ Fruit protection

Physiological fruit drop in longan is lighter than in lychee, but in the young fruit stage it is easily affected by adverse weather and insufficient nutrients, causing heavy fruit drop. Therefore, spray Guoteling once each 7 days and 30 days after flower drop and in late June; foliar fertilization can also be used for fruit protection, such as spraying Shengduosu, Cuikang Shengli liquid, Nongyiqing, and so on.

⑥ Fruit thinning

Longan has a relatively high fruit-setting rate. Some fruiting branches bear more than 100 fruits per cluster, or even 200-300. If fruit thinning is not carried out, the fruits at maturity are small and uneven in size, with no market competitiveness and low returns. Therefore, fruit thinning must be carried out. Fruit thinning should be done when the fruits are the size of a peanut (that is, mid-to-late May). The number of fruits retained generally depends on variety and tree vigor: retain more on vigorous trees and fewer on weak trees; retain more on inner canopy branches and fewer on outer branches; retain fewer in an on year and more in an off year. For example, retain 30-40 fruits per cluster for Chuliang Guangyan, 50-70 fruits per cluster for Shixia, and 60-80 fruits per cluster for Dawuyuan. Thin out overly dense small fruits, twin fruits, deformed fruits, and diseased and pest-damaged fruits. In addition, cut off fruit clusters with fewer than 10 fruits.

Pest and disease control

The main diseases of longan include leaf spot, downy mildew, sooty mold, and anthracnose, and the main insect pests include stink bugs, fruit borers, psyllids, white moth planthoppers, leaf roller moths, and scarab beetles. In addition to strengthening management and doing a good job of orchard sanitation, chemical control can be used.

1. Diseases

Leaf spot can be controlled with 1:1:100 Bordeaux mixture, copper oxychloride at 600-800 times, or Daconil M-45 at 600-800 times; downy mildew and sooty mold can be controlled with thiophanate-methyl at 1000 times or Daconil M-45 at 600-800 times; the pathogen of anthracnose is a fungus, so fungal control methods can be used.

2. Insect pests

Stink bugs can be controlled with 90% trichlorfon at 800-1000 times, Kung Fu at 2000-3000 times, or Arriq at 1000 times; fruit borers can be controlled with Miebaike at 1000 times, Arriq at 1000 times, or Sumicidin at 1000-1500 times; psyllids can be controlled with 80% dichlorvos at 800 times or isocarbophos at 1000 times; white moth planthoppers can be controlled with 80% dichlorvos at 1000 times, or 80% isocarbophos at 1000 times, or Supracide at 1000 times; leaf roller moths can be controlled with 90% trichlorfon at 800 times, or 80% dichlorvos at 1000 times; scarab beetles can be controlled with 90% trichlorfon at 800 times, or 80% dichlorvos at 800 times; carpenter moths can be controlled with 25% dimehypo at 500 times, or 40% dimethoate at 500 times; inchworms can be controlled with 90% trichlorfon at 800 times, or 40% dimethoate at 500 times; scale insects can be controlled with 40% Supracide at 1000 times, or 40% omethoate at 1000 times; mites can be controlled with 40% dicofol at 1000 times, or 5% hexythiazox at 2000-3000 times.