Autumn Management Techniques for Longan: Restoring Tree Vigor, Striving for High Yields the Following Year

    Whether autumn longan management is done properly directly affects whether the longan tree's vigor can be restored that year and whether the following year's yield can be high. Based on fruit growers' many years of experience cultivating longan, the autumn management techniques for longan have been summarized.

Fertilizing Longan

    I. Restore tree vigor and enhance stress resistance.The nutrients of the longan tree have been greatly consumed after several months of bearing fruit. In the 4 months of autumn management from August to November, this is the key to whether the longan can achieve a high yield the following year. Pre-harvest and post-harvest fertilizers for longan must be applied promptly and in increased amounts to promote longan enlargement, raise longan yield and quality, and at the same time restore the longan tree's vigor, enhance stress resistance, and lay the foundation for excellent longan production the following year. As for the specific amount of fertilizer, taking each longan tree producing 100 jin of longan as an example, 15 days before harvest, apply 2 kg per tree, mainly quick-acting fertilizer, using imported compound fertilizer, applied after rain or when irrigating; for post-harvest fertilizer, apply 2 kg of ternary compound fertilizer and 100 kg of human excrement and urine per tree. Dig a trench 20-30 cm deep directly below the vertical line of the canopy edge, cover with soil after application, and if conditions permit, combine with orchard irrigation to increase soil moisture, improve the longan tree's fertilizer absorption effect, and accelerate the restoration of the longan tree's vigor.

    II. Cultivate fruit-bearing mother branches to lay the foundation for excellent production the following year.The best fruit-bearing mother branches of longan are the last mature autumn shoots, so after longan picking, promptly strengthen water and fertilizer management of the longan mother trees to promote autumn shoot sprouting and cultivate the autumn shoots into strong fruit-bearing mother branches. The uniformity of autumn shoot sprouting can be controlled through water and fertilizer.

    III. Pruning and shaping.A longan tree with a good canopy can increase longan yield per unit area, so longan trees should undergo shaping and pruning twice a year. Spring pruning should be combined with flower thinning and fruit thinning; autumn pruning should be combined with tree shape and canopy, retracting overly vigorous branches (referring to young bearing trees), and pruning away weak branches inside the canopy, branch stubs after fruit harvesting, diseased and pest-infested branches, and crossing branches, to improve ventilation and light penetration inside the canopy, restore the longan tree's vigor, naturally regulate the balance of endogenous hormones in the longan tree, and ensure the following year's longan flowering rate.

    IV. Pest and disease control.Autumn temperatures are suitable, so attention should be paid to pests such as longan psyllids, fruit borers, and Conopomorpha sinensis. For pest control, during the peak hatching period of larvae or the early stage of new shoot sprouting, comprehensively spray pesticides for control. In combination with controlling other pests, use: (1) 20% fenpropathrin 2000 times or 10% bifenthrin 2000 times solution for spraying and killing; (2) 2.5% deltamethrin 2000 times solution for spraying and killing, spraying once every 15 days until the new shoots mature. Diseased branches should be deeply pruned, water and fertilizer management strengthened, and robust buds and shoots cultivated.

    V. Transform low-yield orchards.In autumn, temperatures decline and longan root activity increases. At this time, low-yield and neglected longan orchards should undergo hole protection and soil improvement, increased application of organic fertilizers, improved soil structure, increased soil aeration, water retention, and fertilizer retention capacity, and enhanced soil fertility. In addition to applying sufficient nitrogen, phosphorus, and potassium fertilizers, other fertilizers needed by longan should also be applied, and trace elements should be sprayed on the foliage to ensure what longan growth requires. At the same time, the soil should be loosened, longan fibrous roots renewed, root activity improved, longan tree vigor rejuvenated, and strong fruit-bearing mother branches cultivated to lay the foundation for fruiting the following year.