Complete Guide to Longan Cultivation Techniques: A Comprehensive Explanation of Cultivation and Management

Fruit retention, fruit enlargement and crack prevention work begins at flowering. Fruit retention, fruit enlargement and crack prevention in longan are important steps for achieving high and stable yields. The main measures are as follows:

[1] Create good conditions for pollination and fertilization

After flowering, longan fruit can only grow and develop after pollination and fertilization. Creating good conditions for pollination and fertilization can increase the fruit-setting rate and raise yields. The main measures are: (1) place bees in the orchard during the flowering period to improve pollination efficiency in the orchard; (2) if it rains during the flowering period, shake the trees promptly to shake off faded flowers and water droplets on the flower clusters, preventing "flower soaking."

[2] Apply fruit-enlarging fertilizer

The growth and development of longan fruit requires the absorption of large amounts of nutrients. If nutrients are lacking during the fruit growth and development period, it will cause heavy fruit drop and leaf drop, lead to tree decline, or cause poor fruit development and extremely poor quality. Therefore, for high-yielding trees, fruit-enlarging fertilizer must be applied to ensure normal fruit development, improve yield and quality, and prevent tree decline. Fruit-enlarging fertilizer is mainly quick-acting fertilizer, applied simultaneously to the root zone and to the leaves.

The specific practices are as follows:

a) Apply the first fruit-enlarging fertilizer around flowering from late March to early April, which can promote young fruit development and increase the fruit-setting rate. The fertilizer rate is calculated for a 5-6 m canopy, applying 50-100 kg of bran water per tree (containing 1-1.5 kg of dry bran) or 1-1.5 kg of compound fertilizer.

b) Apply the second fruit-enlarging fertilizer from mid-June to early July, applying 50 kg of bran water plus 0.5 kg of urea per tree, or 1 kg of compound fertilizer plus 0.5 kg of urea.

c) Apply foliar fertilizer several times during the fruit growth and development period, which can effectively supplement nutrients. Spray "Nutrient High-Yield Formula" once after longan flowers fade, then repeat once every 20 days, for a total of 3-4 sprays during the entire fruit development period. This has a very good effect on improving fruit yield and quality, increasing single-fruit weight and sugar content, and reducing fruit drop and fruit cracking.

Planting techniques

Longan trees are suitable for growing in subtropical hilly and mountainous ecological environments, especially gentle-slope hills. Under conditions of a long frost-free period, abundant heat, sufficient sunlight, ample rainfall and acidic red soil, developing longan production and establishing export-oriented longan production bases is relatively suitable.

(1) Orchard site selection. Longan prefers warmth. It can grow normally on pond banks, embankments, flat land, mountain foot slopes and hillsides where there is no frost in winter or only brief light frost. Hillsides with especially abundant sunlight, good air circulation, few frost, pest and waterlogging hazards, relatively thick soil and good drainage are even more suitable for longan production, but note that excessively low-lying and damp places are not conducive to longan planting. In addition, slope aspect, gradient, soil properties and soil depth should be considered when selecting an orchard site. In areas with frequent frost in winter, it is better to focus on choosing south-facing or southeast-facing slopes. In coastal areas, leeward slope aspects should be chosen for planting. For mountain slopes, a gradient of 5-25 degrees is suitable; slopes greater than 25 degrees make soil and water conservation relatively difficult. When selecting soil, sites where the surface layer is sandy loam or loam and the subsoil is clay will produce low yields and a short economic life when planted with longan. Red soil or loam, sandy loam and gravelly loam with deep soil layers and a soil pH of 5.4-6.5 are most suitable for cultivating longan. Soil quality near lower slope areas is better than that of middle and upper slopes. For longan, deep soil is an important condition for orchard establishment; usually a soil layer of about 2 m is needed to ensure year-round water and nutrient supply for longan trees. When establishing and planting orchards on a large scale, whether transportation is convenient should be considered. In typhoon areas, windbreak belts should also be arranged. In Fujian, Taiwan, China, and Guangdong, casuarina equisetifolia, Taiwan acacia, Chinese tallow tree, chinaberry, eucalyptus and bamboo are mostly used as windbreaks, which is beneficial for reducing wind damage, decreasing water evaporation, raising and stabilizing microclimate temperatures, and protecting normal growth and fruiting of longan trees.

(2) Soil and water conservation on hillside land. Soil and water conservation is directly related to the growth, high yield and stable yield of longan trees, because longan trees mostly grow in red soil areas with relatively poor physical and chemical properties. These areas often have heavy rainstorms, which very easily cause serious soil erosion. Therefore, it must be emphasized that planting should be carried out only after building terraces or simple soil and water conservation works according to local conditions. When establishing an orchard on gentle slopes of 5-10 degrees, the method of digging "contour hillside trenches" can generally be used to conserve soil and water. The key technical points lie in the trench spacing and depth of the hillside trenches. Where the slope is relatively small and soil erosion is not serious, the trench spacing can be wider, reaching 8-10 m. When digging trenches, pile the excavated soil along the outer side of the trench to form a ridge. If the slope is relatively large and the section has heavier soil erosion, the trench spacing should be reduced to 4-6 m. A large amount of production practice shows that when planting methods, soil biological cover and soil management are properly coordinated, using the "contour hillside trench" method not only saves labor but also creates a stable ripening environment for the soil. When the slope is above 10 degrees, because the terrain is steeper, the method of "contour hillside terraces" is usually used to prepare the land. This is a long-term soil and water conservation engineering measure. For larger longan farms, issues such as the width of the contour hillside terrace platform and its slight inward slope, the height and firmness of the terrace ridge, the solidity of the terrace wall, the rational arrangement of the water storage and drainage system, as well as roads, windbreak belts and fruit collection and distribution sites, should be considered at the same time during orchard establishment and implementation of soil and water conservation works. Terraces should be built level by level from bottom to top along contour lines. A raised soil-conserving ridge should be built along the outer edge of each terrace platform so that rainwater is retained on the platform. A ditch should be made along the inner edge of the terrace platform and connected to the main drainage ditch so that excess rainwater is discharged. The width of the terrace platform depends on the size of the slope. On steep slope sections, the terrace platform is narrower and the terrace wall is higher; on gentle slope sections, the platform is wider. The terrace wall is correspondingly lower. Usually when the slope is about 10 degrees, the platform width can reach 8-15 m and the terrace wall height is about 1 m. When the slope is 11-25 degrees, the platform width is 3-9 m and the terrace wall height is between 1-3 m. Stones can be used to build the terrace wall.

Sod soil can also be used, or red soil can be directly compacted to build the embankment, and green manure or other intercrops can be planted to prevent erosion. When building terrace platforms, the platform surface should have a slight inward slope of 1-2 degrees. The ditch inside the platform is generally about 30-40 cm wide and 15 cm deep. The main drainage ditch can make use of natural water channels, or be artificially built according to the slope and natural water flow paths, and can be paved with stones. In locations with relatively large slopes, "buffer pits" should be added to the main drainage ditch. Place crushed stone at the outlet to slow the impact force of water, and at the same time retain more water and silt washed down. If the orchard is selected on a relatively steep hillside, in order to prevent mountain floods from woodland above the orchard or from the mountaintop from rushing into the orchard, a wide and deep interception ditch can be opened at the uppermost part of the orchard, with a depth of 0.3-0.6 m and a width of 0.6-1 m. The interception ditch should connect with the drainage ditch. When the interception ditch is too long, there should be an appropriate segmented gradient to facilitate drainage. To make full use of rainwater, small water storage ponds can also be dug in appropriate sections of the drainage ditch to reduce soil and water loss.

(3) Field planting. Field planting should be carried out in spring and autumn, with spring planting preferred. Spring planting is done before spring buds sprout or after spring shoots have grown and matured, generally from February to May, with April being suitable. Autumn planting is done before autumn buds sprout or after autumn shoots have matured, generally from August to October.

Because red soil hilly land or other hillsides have thin soil and relatively poor physical and chemical properties, holes should be opened 2-3 months before field planting to sun-dry the soil. Production practice has shown that large holes are beneficial to seedling growth. The holes are usually 0.6-1 m deep and about 1 m in diameter. After opening the holes, apply sufficient basal fertilizer. Basal fertilizer can be obtained locally, using green manure, weeds, barnyard manure, compost, garbage or pond mud, etc. According to the fertilizer source situation, apply about 5 loads (250 kg) per hole, and mix in a small amount of lime, phosphate fertilizer, cake fertilizer, etc., applying them in layers and mixing them evenly with the soil. When digging holes, the topsoil and subsoil should be kept separate, and when filling soil, put the topsoil in first. Planting density in mountainous areas is generally 6 x 7 m, about 15 trees per mu. Plots with better fertility should be appropriately denser, 5 x 5 m, about 25 trees per mu. Use dwarfed low-stem cultivation to help obtain early-stage yield.

At field planting, consider that after survival the root crown of the plant should be level with the ground surface, and it should not be too deep or too shallow. At field planting, the root crown can be required to be 5-6 cm above the ground. Before planting, the pit should also be fully irrigated in advance. After the water seeps in, place the seedling with an intact root system or with soil, carefully fill in soil according to the above requirements. Do not fill all the soil at once; fill it in layers, and gradually press inward from the outer edge with the hands so that the soil and roots are in close contact. Never tread with the feet, as this easily crushes the soil ball and causes young roots to break. After field planting, make a small water basin around the seedling to facilitate irrigation. To reduce leaf evaporation and help survival, part of the small branches and leaves can be pruned off. After planting, irrigate thoroughly. After all the water has been applied, spread a layer of fine soil to prevent the soil from cracking and tearing the young roots. If drought occurs, water once every 3-5 days.

To increase economic benefits per unit area, during the initial period of regular planting, short-term crops can be systematically intercropped to support long-term development with short-term returns, and this can also conserve fertilizer and soil. Business website: www.3456.tv

[4] Control fruit-stage pests

Damage to longan fruit by the lychee stink bug or the lychee fruit borer is an important cause of fruit drop, especially late-stage fruit drop. Therefore, control work must be done carefully in production.

(1) Control methods for the lychee stink bug

In Guangdong production areas, generally spray once with 80% dichlorvos 800-fold solution in early March (around Awakening of Insects), and spray once with 90% trichlorfon 600-fold solution or 10% mibaioke 1500-fold solution in late March to kill overwintering adults. From late April to mid-to-early May, spray 1-2 more times with trichlorfon or pyrethroid pesticides to kill young nymphs.

(2) Control methods for the lychee fruit borer

Do a good job of pest monitoring and forecasting, and spray once each when adult emergence rates reach 40% and 80%. If pest monitoring and forecasting have not been done, spray once in early July and once 15 days before harvest. Commonly used pesticides: 25% quinalphos emulsifiable concentrate 800-fold solution, 49% chlorpyrifos 1200-fold solution, 10% mibaioke 1500-fold solution, 25% dimehypo aqueous solution 500-fold solution, 90% trichlorfon 600-fold solution, etc.

In addition, doing a good job of winter orchard cleaning can effectively reduce damage to longan by the lychee stink bug and the lychee fruit borer.

[5] Irrigation and drainage

During the fruit growth and development period, maintaining the water balance of the soil and tree is an important measure for enlarging fruit, retaining fruit and preventing cracking in longan. Therefore, irrigate promptly during drought and drain promptly during heavy rain.

[6] Application of growth regulators

In recent years, growth regulators have been widely used in production to retain fruit, enlarge fruit and prevent cracking, improve fruit quality, and increase yield with obvious results.

(1) Commonly used agents include:

5 mg/L gibberellin plus 5 ml/L 2,4-D aqueous solution, longan-specific fruit-retention formula, Guoteling No. 1, etc. Spray the first time 10-15 days after longan flowering, then spray once every 20 days, for a total of 2-3 sprays.

(2) Other reports indicate:

Starting 50 days before harvest (when the seeds are just about to turn black), begin spraying compound triacontanol (TA) milk powder, then spray once every 10 days for 3 consecutive sprays, which can significantly improve longan yield and quality.