The heavy snow has arrived and the temperature is gradually decreasing. For the citrus that has not been harvested, if the temperature drops sharply, it is easy to suffer from freezing damage. In the mild case, the flower buds are frostbitten, and the leaves are severely fallen. In the severe case, the dry and dead skin layer of branches will be cracked, and it will also cause cracking, rotten fruit, fruit drop or peel frostbite browning, dry water, etc.

In addition, fruit trees damaged by freezing are also prone to disease, which seriously affects tree vigor, yield and profit, and even freezes to death of the whole plant. Therefore, it is particularly important for citrus to prevent cold and freeze.

1. Physical methods

1. Irrigate before freezing

It can increase soil water content and air humidity, reduce ground radiation, accelerate the upward conduction of deep soil temperature, and reduce freezing damage. It is carried out when the temperature is high at noon, and the amount of irrigation is based on the principle of irrigation, drained immediately after irrigation, no water accumulation, and timely cultivation to prevent freezing after irrigation.

Analysis: It is necessary to grasp the amount, too much can easily cause accumulation of water, which will affect the root respiration and aggravate the consequences of frost damage. Too little can not achieve the purpose of antifreeze.

2. Cultivate soil to increase temperature

Soil cultivation in winter can increase soil temperature and increase fertility, so as to achieve the purpose of protecting root system and root neck. Red soil hilly land is best to cultivate sand, pond mud or turf. The height of the cultivating soil should be 35cm higher than the mating interface and above the ground. After the frost period in the spring of the second year, the soil should be opened to prevent the rhizome from rotten.

3. Whitening the trunk

Citrus rootstock joints and root necks are the weakest parts of the cold resistance. The white reflection of lime is used to reduce the temperature difference between day and night of the tree, avoid frostbite of the trunk, and at the same time eliminate the overwintering pests hidden on the trunk. The whitening height should be below the first main branch.

4. Cover film or grass

After covering, it can reduce the freezing damage caused by advection cooling and intense radiation cooling, especially suitable for sunny freezing and frost damage after snow. In addition, wrapping the trunk with straw before freezing can also prevent freezing and cold. It is an ideal way to change the local microclimate.

Fighting mulching, direct mulching and tree trunk wrapping

Comparative analysis

1. Scaffolding film: high cost, suitable for areas that often need to be antifreeze

2. Direct film mulching: Long film mulching will cause poor ventilation of fruit trees, weaken leaf respiration, hinder photosynthesis, affect the quality of flower bud differentiation, and cause leaf yellowing in severe cases

3. Trunks for grass: Trunks for grass have a certain effect on the middle and lower parts of the trunk, but it has a good effect on the crown part, especially when there are fruits.

5. Smoke and cold protection: Before cooling down, pile up branches and leaves, weeds, sawdust, chaff, etc. in the citrus orchard, and press the soil to form a smoke pile, leave the ignition and smoke outlets, and ignite and smoke before the low temperature. It produces a lot of smoke, which can reduce the radiation and increase the temperature of the orange orchard and prevent frost.

Analysis: The effect is good in a short time, and it can cope with rapid temperature drop.

2. Chemical methods

1. Apply amino acid fertilizer

Spraying amino acid fertilizer before and after freezing damage can absorb faster in low temperature environment. And timely replenishment of trace elements is conducive to increase the resistance of fruit trees and quickly restore tree vigor.

Analysis: An ideal anti-freezing method is effective for general cold damage and freezing damage, but it must be sprayed some time before the cold wave arrives so that the tree can fully absorb it. Amino acid fertilizers enhance tree vigor and improve the stress resistance of citrus.

2. Spray plant antifreeze