The apricot tree is native to my country and has a long history of cultivation in my country. Apricot trees are resistant to barrenness, drought and cold, and are often used as excellent tree species to improve the ecological environment and increase farmers’ income. In recent years, the apricot (kernel, fresh food) industry has become a pillar industry for poverty alleviation in poor mountainous areas and the construction of beautiful villages. However, apricot trees bloom early and are vulnerable to severe weather such as low temperature in early spring and late frost, which in turn causes freezing damage and severely affects and restricts the development of the apricot industry. The temperature during the flowering period of apricot trees varies greatly, especially in the northern apricot producing areas. Cold currents and strong winds are often encountered from March to April. When the temperature is lower than the critical temperature that apricot flowers and young fruits can tolerate, the apricot The flower buds, flowers, and young fruits of the tree caused freezing damage, resulting in reduced or no harvest of apricots.
In mid-to-late April 2020, northern apricot producing areas such as Gansu, Hebei, Ningxia, and Xinjiang, especially Zhangjiakou, Hebei, Guyuan, Ningxia, etc., suffered severe cold in spring, which caused a decline in apricot production and no harvest, and farmers’ income was affected. Great loss. Take the freezing injury of apricot flowers in Yuanzhou District, Yinchuan City, Ningxia in 2020 as an example:April 11-12, the lowest temperature was -10℃ and lasted for 2 days, fresh apricots and mountain apricot flowers were seriously damaged (more than 50%); April 24 On the day, the temperature is -20~-10℃, and the young fruit stage suffers from late frost damage. As a result, the local apricot production area in 2020 suffered severe frost damage to mountain apricots, kernel apricots, and fresh apricots, and most of them were not harvested. This article discusses and summarizes the causes of freezing damage of apricot trees, the prevention measures of freezing damage and the post-disaster remedial measures, in order to provide valuable reference suggestions for the management of apricot orchards and industrial development.
Causes of low-temperature freezing damage and its effects on apricot trees
Causes of freezing damage to apricot trees
The influence of climate factors
Apricot trees are more resistant to cold, but apricot trees are the earliest deciduous fruit trees that bloom. The temperature changes in early spring and the occurrence of late spring cold is more common. The main causes of frost damage are:frost is formed by lowering temperature and frost in early spring; the temperature rises rapidly during the day and the temperature is low at night in early spring, and the temperature changes greatly. Apricot trees are most susceptible to late frost and low temperature damage during the spring blooming and young fruit stages. During the temperature rise, the apricots are released from dormancy and begin to bloom and germinate. However, the sudden arrival of drastic temperature changes, especially low temperatures, freezes the active cell tissues. It can cause freezing damage or low-temperature sun burns on branches and trunks, frozen flowers, and frozen fruits, resulting in reduced or unstable yields of apricot trees. According to investigations, the temperature in the bud stage is lower than -3.9°C, the flowering period is lower than -2.2°C, the young fruit stage is lower than -0.6°C, and the low temperature lasts for more than 30 minutes, which is likely to cause freezing damage to flowers and fruits. Apricot trees have different tolerance to low temperature in different growth stages:the bud germination period is stronger, followed by the full bloom period, and the ovary expansion period and the young fruit period are the weakest.
The direct cause of the freezing damage of apricot trees in 2020 is that the temperature rises rapidly before the arrival of the cold wave, and then the cold air hits, the temperature drops sharply, and the low temperature weather lasts for a long time. Taking Guyuan City in Ningxia as an example, according to meteorological data, the highest temperature reached 19℃ on April 8-10. The high temperature for 3 days broke the dormancy of the tree body, the sap began to flow, and the apricot tree entered the flowering growth period from the dormant period; From April 11 to 12, the temperature dropped sharply to -2.0~-1.0℃ for nearly 8 hours. At this stage, the flower buds began to swell, the bud scales became loose, and the internal physiological activities of the buds were relatively vigorous. It was more sensitive to low-temperature weather, caused by low temperatures below 0°C. The internal cell structure of the flower buds was destroyed by freezing, leading to necrosis of the tissues in the flower buds, and then browning and drying up, resulting in severe freezing damage in most areas of the spring apricot production area in 2020, and almost no harvest. The occurrence of freezing damage in different apricot producing areas is shown in Table 1.
The influence of terrain conditions
In Xinghua Mountain, Zhenping County, Henan Province, three representative plots, namely the top of the hilly slope, the flat land in front of the Nangang slope, and the bottom of the ditch, were selected for frost damage investigation. Because of their different environmental conditions, they will form very different microclimates, and the degree of freezing damage of apricot trees is obviously different.
It can be seen from Table 2 that at the bottom of the ditch in the middle and lower part of the hillside, the underlying surface is a bare hillside. Due to direct sunlight, the ground temperature and air temperature will rise rapidly. The phenological period of apricot trees will be 2~3 days earlier than that of the hillside. Moreover, the terrain here is relatively closed. When the cold wave comes, the cold air is easy to gather and sink, and the freezing damage of the trees is the most serious. The freezing damage rate is 100%, and the freezing damage index is as high as 85%. On the flat land in front of the Nangang slope, the ground is farmland, and the degree of frost damage is less than that of the downslope and the bottom of the ditch; on the top of the hilly slope, the terrain is open, the altitude is high, the vegetation coverage of the underlying surface is large, the phenology period is delayed, the frost damage is relatively light, and the freezing damage The rate is 65%, and the freezing damage index is only 35%.
Impact of freezing damage on apricot tree and apricot fruit yield
Frost during flowering is one of the main factors affecting the yield of apricot trees. The weather gradually warms up in spring, but the reciprocating changes are extremely unstable. If cold air strikes and the temperature drops sharply, it will cause greater harm to the almond trees. The cold spring will cause different degrees of freezing damage to the branches, flowers, young leaves, main branches and even the whole tree of apricots (Figure 1~Figure 5). When the frost damage is severe, the flowers wither, and the main branches and trunks are frostbitten. When the flowers are blooming, the late spring cold comes, which is not conducive to normal pollination and fruit setting; when the fruit is set, the late spring cold comes, causing frostbite damage, growth arrest and shedding of the young fruit, resulting in a reduction in production, and no harvest in severe cases.
frost damage prevention measures
adapt to the site and adapt to the tree, scientifically build a garden
(1) Choose a reasonable address to build the garden. Building gardens on slopes in mountainous areas requires leeward wind and sunny, and gardens on flat grounds require a gentle terrain and good water and fertilizer conditions. Try to avoid low-lying land, shady slopes, and ditch bottoms and vents where cold air is trapped. In Xinjiang, Inner Mongolia and other northwestern regions with heavy sandstorms in spring, shelterbelts have been built around the park.
(2) Select low-temperature and cold-resistant varieties. When planting apricot trees in areas with frequent low temperature and late frost, apricot varieties with late flowering and strong cold resistance should be selected to avoid the frost period, adapt to the low temperature environment, and reduce the harm of late frost. This is the most direct and effective defense measure.
Prevent coldness in spring
When the apricot tree buds and is about to bloom, always pay attention to the weather forecast, and take timely and active measures to avoid or reduce the frost and cold damage to the apricot tree body, flowers and fruits The harm. Firstly, strengthen tree management; secondly, take measures such as irrigation, smoking, installation of fans, spraying and other measures to defend against local conditions according to different situations.
Strengthen soil and tree management in orchard,
Enhance tree resistance
After being frozen, the orchard should be lightly hoeed to loosen the soil in time to promote the growth of the root system, thereby ensuring the normal growth of the tree body and providing nutrients for the sitting fruit. Strengthen tree body and soil management, enhance tree vigor, increase the fullness of flower buds and the resistance to low temperature weather. Do a good job of plastic pruning, control the occurrence of pests and diseases, rationally apply organic fertilizers, and add phosphorus and potassium fertilizers to ensure the health of the tree, promote the maturity of the branches, and improve the cold resistance and frost resistance of the fruit tree.
winter tree body painted white
Whitening the tree body after leaf fall can not only protect the tree body and reduce the occurrence of diseases and insect pests, but also delay the flowering period and prevent the early spring temperature from being too low and the branches and flowers from being damaged by freezing. The whitening agent is sold as a special finished product, or it can be prepared by yourself.
When low temperature comes, smoke in the whole garden can increase the temperature in the orchard by more than 2℃, disperse or reduce the sinking of cold air, and play a role in preventing and avoiding low temperature. The smoke pile should be placed in the upper air vent of the orchard, and each pile uses 20-25kg of firewood and 6-8 piles per mu is suitable. First, install low-temperature early warning devices in the field, and according to weather information or low-temperature pre-alarm information, put the prepared smoke piles in time to achieve the purpose of preventing frost damage.
Use irrigation or spraying method to postpone the flowering period
Spraying antifreeze agents such as bugibberellin on the tree body before falling leaves in autumn can improve the frost resistance and delay the flowering period for 3~5 days; spray cyanoxin, naphthalene acetate potassium salt, 0.5%chlorine in the early spring flower bud expansion period and early germination period Calcium can delay the flowering period by 5~7d. Due to the large differences in climatic conditions from place to year, the time of freezing damage and late frost is uncertain, and the time and amount of spraying are not easy to grasp. Delayed flowering can only slow down to a certain extent, and it cannot be avoided fundamentally when a large drop in temperature occurs. Solve the night frost hazards of apricot trees.
Irrigate the whole garden before the low temperature, which can not only supplement the moisture of the tree, but also increase the air humidity, reduce the ground radiation, increase the dew point temperature, especially before the germination, the flowering period can generally be delayed by 2~3d to avoid Open the cold current to minimize the risk of frost.
Take remedial measures to reduce
frost damage loss
artificial pollination or bee pollination
When an apricot tree encounters a slight low temperature frost during the flowering period, the pollen activity will be reduced, the pollination effect will be poor, and the fruit setting will be poor. Therefore, artificially assisted pollination is adopted for the apricot orchard with less frost damage, and 0.2%~0.3%borax+0.3 is sprayed.%~0.5%urea mixture can increase the fruit setting rate.
Putting bees in the orchard can effectively increase the fruit-setting rate of apricot trees, but when the temperature is lower than 15℃, the pollination activity of the bees in flight will decrease, which will greatly affect the pollination effect of the bee colony on the apricot flowers. In order to stimulate the enthusiasm of bees to collect apricot pollen, spray 0.3%~0.6%honey water or 0.6%~1.0%sugar water on the flowers during the flowering period, which can significantly improve the pollination effect of bees and increase the fruit setting rate.
Auxiliary pollination and preservation of flowers and fruits
After the frost, cut off the severely frozen flower branches in time, protect and use the unfrozen or lightly frozen branches and flowers, and artificially assist in pollination; when the young fruit is frozen, do not rush to thin the fruit, but wait After the effects of natural fruit falling and freezing damage, deal with it according to the actual situation.
Timely top dressing and foliar spraying of quick-acting fertilizer
After freezing damage occurs, the orchard can be combined with watering and timely fertilization, or foliar spraying of nitrogen fertilizer (containing zinc) and other quick-acting nutrients to promote the growth of apricot trees, and strive to keep the flowers and fruits free from freezing damage and obtain a certain yield; at the same time; Supplementing nutrient elements can increase the efficiency of photosynthesis and promote the production of sufficient nutrients on the leaf surface to facilitate the rapid recovery of the tree’s vigor and promote the normal growth of the tree.
Account:This article is an excerpt from”Chinese Fruit Tree” Issue 6,”Apricot Freezing Damage and Preventive Measures” (Chen Yuling, Song Wenqing, Xia Lehan, Chen Long) , Huang Zhenyu).