What is the freezing injury of fruit trees and what preventive measures are there?

Freezing injury is an agricultural meteorological disaster. That is, the low temperature below 0℃ causes crops to freeze and causes damage to crops.

Choose a suitable garden: for newly developed orchards, try to choose a place with the lee and the sun, and avoid building gardens in low-lying areas or shady slopes. Because this place cools down early in autumn, warms up slowly in spring, and stops accumulating cold air in winter night, the temperature is very low.

Selection of Cold-tolerant Tree Species and Varieties: Gardens should be built in cold areas according to local climatic conditions, and trees should be planted in suitable places.

Selection of cold-resistant rootstock: select rootstock seedlings with strong cold resistance, or use rootstock seedlings with strong cold resistance to build gardens and graft new, excellent, rare and special varieties to improve their cold resistance. For example, the mountain stator in apple rootstock has stronger cold resistance than begonia.

Strengthen cultivation management: pay attention to timely drainage in years with more autumn rain and orchards with high water content; Fertilization should be based on organic fertilizer, increase the application of phosphorus and potassium fertilizer, control the amount of nitrogen fertilizer (especially in the middle and late stages of fruit tree growth, with little or no application), and urge fruit trees to end their growth ahead of schedule and enter the dormancy period in due course; Strengthen pest control, protect the integrity of leaves including autumn leaves, improve the photosynthetic efficiency of leaves, increase the accumulation of nutrients in trees, promote the maturity of branches and improve the self-freezing ability of trees.

Irrigation in winter and spring: Before the soil freezes in winter, the frozen water should be irrigated once, and this irrigation should be thoroughly poured. The heat capacity of water is higher than that of soil. Irrigation before winter can achieve the function of heat preservation and warming, and prevent freezing injury. Watering fruit trees before germination in early spring can not only prevent soil drought, but also reduce the ground temperature, delay the germination and flowering of fruit trees, and achieve the purpose of preventing freezing injury at flowering stage.

Reasonable pruning: pay attention to control the flourishing length of fruit trees in summer pruning, and stop the growth of branches in time to make them fully developed; When pruning in winter, we should pay attention to cutting off immature branches; When thinning large branches, protective agent can be applied to the cutting mouth to prevent the cutting mouth from freezing injury due to low temperature. Scientific pruning can not only improve the yield of fruit trees, but also effectively control pests and diseases, enhance the nutrient accumulation of trees, which is conducive to cold resistance and overwintering.

Cold protection of young trees: in cold areas, it is best to bury the newly planted young trees in the winter of that year to prevent cold; If you can't bend down, you should pile a conical mound around the root, which is about 30 cm high and tamped to prevent ventilation, and then cover it with a layer of dry fine soil to prevent water evaporation. For those who can't bend over to bury the soil, a semi-crescent ridge with a height of 60-70 cm and a width equivalent to that of the trunk can be planted in the northwest direction about 50 cm away from the trunk as a barrier, so as to change the microclimate conditions around the tree, raise the soil temperature, shorten the soil freezing period, and make the fruit tree roots absorb the water in the soil in time to reduce or prevent peeling.

Bundle straw: before winter, wrap straw or straw rope around the trunk or main branch, which can not only prevent the cold wind from attacking, but also reduce the water loss of the trunk. After germination in spring, the unbound matter should be burned or buried deeply to eliminate overwintering pests and diseases.

Whitening the trunk: after the leaves of the fruit tree are fallen, the trunk and main branches of the fruit tree are evenly whitened with whitening agent, so that the temperature of the tree body changes smoothly and there will be no freezing and thawing phenomenon, which not only prevents freezing injury and sunburn, but also kills germs, eggs and adults hidden in the trunk. The coating liquid should be dry and thin, and it is advisable not to flow when brushing. The proportion of white coating liquid is: quicklime 100, sulfur powder 10, salt 10, vegetable oil 1 0, and water 200 (parts by weight), and the mixture is evenly mixed.

Orchard smoking: Generally, smoking can increase the temperature by 3-4℃, reduce the radiant heat on the ground, and at the same time, smoke particles can absorb the moisture in the air. This method is particularly effective in low-lying orchards where cold air tends to gather in winter. Its practice is to use chopped firewood, chopped weeds, sawdust, chaff shells and waste kerosene as fuel in the evening before the cold wave comes, and ignite when the temperature drops to the critical temperature of frozen fruit trees to control the smoke to cover the space in the orchard. Generally, 4-5 ignition points can be set for each acre of fruit trees, and each pile is 15-20k g, and set in the windward.

Spraying saline before flowering: spray 1% physiological saline evenly on the tree before flower bud germination to improve the frost resistance of the tree itself and prevent frost during flowering.

Snow removal: shake off the snow on the tree in time after heavy snow and pile it at the root of the fruit tree to help the soil store water and moisturize.