In the main production areas of fruit trees in northern China, especially in the Bohai Bay area and the Loess Plateau in the northwest, late frost damage is one of the major natural disasters that seriously threaten the safe production of apple, pear, peach, plum, apricot, cherry and other major fruit trees.

After the soil thawing in spring, the northern fruit tree production areas in our country warmed up faster. However, the temperature fluctuates frequently, and strong cold currents or radiation cooling often occur, resulting in rapid cooling. According to nearly 50 years of experience and records, from the beginning of March ("shocking") to the middle of April (before and after the "grain rain"), there will be a cold air in Siberia and Mongolia every 7-10 days. The air forward can drop 6-12°C over an air temperature, affecting 1-3 days. The time, number, frequency, and intensity of cold air in different regions and different geographical conditions are different, but it has always been an important natural disaster that threatens the safe production of fruit trees in the region. Therefore, it is an important task to strengthen the production management of orchards in the spring to take active and effective measures to prevent fruit trees from frost damage.

Since the end of winter and spring, the weather in some parts of China has been abnormal, and many provinces and regions have experienced extreme weather phenomena that have not been encountered for many years. In particular, in mid- and late January of 2008, continuous snowfall over a relatively large area in some parts of the country suffered from cold weather, causing major disasters to agricultural production. In order to prevent the occurrence of possible frost hazards in the spring and cause major disasters in fruit tree production, the technical management suggestions and recommendations for the prevention of late frost damage in fruit trees are listed below for reference by fruit producers in various regions.

(I) The regularity and characteristics of frost frost damage in fruit trees

Late spring frost is very harmful to fruit trees, especially flower buds, flowering and fruit setting. Since the severe winter has passed, the deciduous fruit trees have been released from dormancy, and the ability of various organs to withstand cold damage has been drastically reduced, especially when they encounter severe cold currents after 3-5 days of abnormal temperature rise, they are more vulnerable. The cold resistance of flower organs and young fruits of fruit trees is poor, and late frost damage occurs at the flowering and young fruit stages, often causing major economic losses. Flowering frost, if there is fashion, some late flowers may be frozen lightly or avoid freezing injury and fruit set, can still maintain a certain economic output, while young fruit frost often results in the death of the crop. The late frost damage of flower organs of fruit trees is often accompanied by the reduction and termination of pollinating insect activity, thereby reducing the fruit setting rate. In some cases, remediation measures can be taken when the loss of low-temperature freeze-inducing fruit set is dominant.

The degree of frost damage depends on the meteorological factors such as low temperature intensity, duration, and the speed of temperature rise. The speed of temperature drop is fast, the amplitude is large, and the duration of low temperature is long, the heavier the damage is.

(II) Technical Measures for Preventing Night Frost Damage

1, delayed budding, avoiding frost

(1) Orchard irrigation: The buds of fruit trees are sprayed 2-3 times before flowering, which can delay flowering for 2-3 days.

(2) The tree is painted white or sprayed white: the trunk of the early spring, the main branch of the tree is painted white, or the whole tree is sprayed white to reflect the sunlight and slow down the temperature of the tree, which can delay the sprouting and flowering of the flower buds.

2, orchard spray, prevent frost

Before or after the strong cold air arrives, the continuous water spray in the orchard can effectively ease the temperature drop in the orchard and prevent frost.

3, Orchard smoke smoke warming, prevent frost

Pay close attention to the weather forecast and the observation of local temperature. Before the frost comes, use sawdust, wheat bran, stalks, or weeds cleared in the winter garden to alternately stack and use as fuel. After stacking, press the thin soil layer; or use the hair. Smoke (2 parts of ammonium nitrate, 7 parts of sawdust, 1 part diesel fuel, mixed in a paper tube, plus a damp-proof film) ignited the smoke. The smoke stack is placed at the outlet of the orchard, usually 4-6 piles per acre orchard (the size and amount of the smoke stack depend on the frost intensity and duration); the time for smoking is generally from 10 pm to 3 am the next day ( When the temperature is close to the low temperature critical value tolerated by the flower organs or young fruit, the stack should be ignited in time. Dark smoke and thick smoke are appropriate, so that the smoke can permeate the entire orchard until the morning sunrise. This method can slow down the accumulation of cold air in the orchard near the ground and low air, slow down the process of cooling and cooling, and increase the heat in the near-ground air. It is an easy and effective measure to prevent frost and save time and labor.

4. Covered with orchards to prevent frost

The use of organic materials such as straw, branches, and weeds to cover the tree plate (or the entire orchard) and the orchard film can reduce the effective radiation on the ground and thus prevent frost. Fruit trees nursery frost-proof, can be directly covered in seedling plants. Orchard farming helps to prevent frost.

The occurrence and prevention of frost are closely related to the terrain and topography. Orchard with complex terrain and smoke prevention cream

The freezing effect is not good. Frost in the valleys, basins, and depressions is severe and radiation frosts often occur. Therefore, the cover method is more appropriate.

5, set up a suitable place to prevent frost

To build a new orchard, it is necessary to choose appropriate topography and topography in accordance with the principle of suitable land and trees, and to avoid the construction of a park where frost hazards are likely to occur; consider setting up windbreaks and windbreaks, and making full use of favorable microclimate areas to plant those that are prone to frequent frost damage during flowering. Tree species. And according to the local climate characteristics, select good varieties with strong cold resistance.

6, other measures

According to foreign sources, using a high-power air blower over the orchard to agitate the air can cool the agglutination of cold air and prevent frost.

(c) Remedial measures after frost

1 After the flowering period is frozen, spraying gibberellin under the condition of unsustained torus can promote parthenocarpy and make up for a certain loss of yield.

2 Artificially-assisted pollination is used to promote fruit setting; 0.3% borax and 1% sucrose are sprayed to increase overall fruit setting rate.

3 Strengthen the comprehensive management of soil, fertilizer and water, cultivate roots and trees, promote fruit development, increase single fruit weight, and save production.

(4) Strengthen comprehensive prevention and control of diseases and pests: After the fruit trees suffer frost damage, the trees will be weakened and their resistance will be poor, and they will be prone to pests and diseases. Therefore, we must pay attention to the comprehensive prevention and control of pests and diseases to minimize the production and economic losses caused by pests and diseases.

(4) Suggestions

The prevention and control of frost damage in fruit trees should be based on prevention. Therefore, it is necessary to establish an effective frost forecasting, observation, and early-warning mechanism so that timely response measures can be taken to prevent the occurrence of frost disasters. Specially put forward the following points:

1. Lose chances, increase awareness of prevention, and strengthen technical training. Based on decades of experience, the frequent, variable cold currents in the spring in northern China are the climatic phenomena that occur every year. Therefore, fruit tree producers, fruit production companies, and fruit tree promotion workers must fully understand the objectivity of the cold flow, the possibility and catastrophic occurrence of frost, and increase awareness of prevention. There must be no luck but nothing to do. Early prevention is absolute, rather prevent and not suffering. It is necessary to vigorously promote the scientific concept of predictable and controllable night frost damage of fruit trees, strengthen the cultivation of frost abatement awareness among fruit producers and technology extension workers, increase the popularization and promotion of fruit tree frost prevention and control technologies, and enable the majority of fruit farmers to truly grasp fruit trees. Frost hazard prevention techniques and emergency remedial measures.

2. According to the experience of Shandong Province for many years, the central and provincial TV stations generally issued forecasts and warning information 2-4 days in advance for the severe cold that may cause disasters. Therefore, as long as the ideological attention, pay attention to the cold weather forecast and early warning, prevention and control of frost countermeasures can be implemented in time. However, due to the fact that our country's fruit trees are mainly planted in mountainous areas and hills, with complex topography, topography, and geomorphology, a number of microclimate regions with unique features have been formed. Weather forecasts by meteorological agencies of the state, province, and city (county) are sometimes difficult to predict accurately. The weather conditions in townships (towns) and villages (teams) have changed. Therefore, in the main producing areas of fruit trees, all townships (towns), villages (teams), fruit production companies, fruit production cooperatives, and fruit farmers' associations, in addition to paying close attention to the weather forecasts of the central, provincial, and city (county) television stations, must Establish local weather observing stations (points) to monitor local weather conditions in real time. According to the weather forecast of the national, provincial, and city (county) meteorological departments and the actual local observations, predict the time and intensity of the local occurrence of severe frost, provide real-time warning information for the fruit producers in the jurisdiction, and take timely measures to prevent frost. .

3, to do a good job in advance of fruit trees frost hazard prevention and control of emergency technical measures required for the preparation.

4. Develop new and more effective fruit tree frost prevention and control technology.

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