What are the key points for protecting longan from the cold in winter?

1. Cultivate robust autumn shoots. Autumn shoots are the fruiting mother branches of longan for the coming year and are also one of the main branches for longan to overwinter. Whether the autumn shoots are robust affects their ability to withstand cold during overwintering. Therefore, the last autumn shoots of longan are generally best controlled to emerge in mid to late October; before shoot emergence, it is best to apply 1 light application of nitrogen fertilizer and water, so as to unify shoot emergence and strive for all autumn shoots to mature in early to mid December. Robust autumn shoots can enhance the tree's nutrient accumulation, thereby effectively resisting cold waves.

2. Do a good job of winter orchard cleaning and trunk whitewashing. (1) Remove dead branches and diseased leaves: after the autumn shoots mature, spray with 0.9-1.2 degrees Baumé lime-sulfur mixture to control overwintering pests and diseases. (2) Trunk whitewashing: use 10 kg quicklime and 1 kg sulfur powder, add 30-40 kg water, stir evenly, and mix into a paste; whitewash the main trunk and primary and secondary branches, which can effectively reduce freezing injury.

3. Build up soil around the tree base. In conjunction with deep digging during winter orchard cleaning, spread pond mud, turf, etc. within a 100 cm diameter around the tree base to build up soil to a height of 10 cm above the trunk graft union, which can effectively protect the graft union.

4. Straw mulching and binding. (1) In winter, within a 120 cm diameter around the tree base, cover with rice straw, corn stalks, rapeseed stalks, etc. to a thickness of 10-15 cm, or cover with plastic film, which can raise soil temperature. (2) Bind the trunk and primary and secondary branches with rice straw, which can help keep the tree warm.

5. Orchard irrigation. Before the temperature drops, lead water into the orchard and irrigate the whole orchard, then drain immediately after irrigation. Where there are no irrigation facilities, carry water to water the tree base; for adult trees, pour 100-120 kg water per plant, which can replenish tree moisture, increase soil and air humidity, raise soil temperature, and reduce freezing injury.

6. Orchard smoking. Before the cold wave arrives, prepare flammable smoke materials such as rice husks, sawdust, and turf in the orchard, place 1 pile every 10 m, and mix in a small amount of waste diesel oil to increase the smoke heat; after 22:00 on the night the cold wave arrives, ignite the smoke materials and use smoke to raise temperature and keep warm to prevent frost damage.

7. Spray water to prevent freezing. If wet freezing occurs, quickly organize manpower to shake off ice blocks on the trees and spray water to thaw them.