The main apple producing areas in Shaanxi Province are prone to freezing damage during the flowering period. Especially in recent years, the warm climate in winter has intensified, the temperature rise in spring has accelerated, and the budding and flowering period of apples has advanced. , The probability of frost damage during flowering increases. Since mid-February this year, the temperature in most parts of northern my country, including the main apple producing areas in Shaanxi, has been generally high. According to the weather forecast, although there was a cooling process in late February, the average daytime temperature after early March is still higher than last year. The higher the temperature, the increase in soil moisture evaporation, and the drought in the main apple-producing areas of our province has been more serious since last winter, and the soil moisture is poor. If the temperature continues to be higher, the bud and flowering period of apple trees will be earlier, and the more early the flowering period will be. The greater the probability of frost damage in flowering period caused by the cold of late spring. Therefore, the majority of apple growers must deeply learn the lessons of the large-scale frost damage during the flowering period in 2018 and the frost damage during the flowering period in some areas in 2020, raise the awareness of prevention, formulate relevant measures as soon as possible, and take preventive measures against the cold in this spring.
The main measures to prevent frost during apple flowering are as follows:
1. Build a garden reasonably
The experience and lessons of previous years show that the location of the garden has a crucial influence on the probability and degree of frost during flowering. From a long-term consideration, when choosing a garden site, you should resolutely avoid low-lying lands, basins, canyons, valley mouths and other areas where cold air is easy to gather and radiation frost is easy to occur. Mountainous land construction should choose the middle and upper part of the slope, and it is strictly forbidden to build a garden in the middle and lower part of the slope. In addition, frost-prone areas should choose varieties with late flowering and strong cold resistance, such as honey crisp, as the main plant varieties.
2. Delay germination and flowering
The practice in recent years has proved that delaying flowering is the most effective measure to avoid freezing damage during flowering. The later the flowering, the lower the probability and degree of freezing damage during flowering. The methods to delay the time of budding and flowering are:(1) Irrigation. Where conditions permit, irrigate 2-3 times in spring to delay soil temperature rise and delay budding and flowering; areas with snowfall in winter should pile up snow in the orchard to cool down as soon as possible; (2) Whitening. Before the Spring Festival, the trunk and main branches should be whitened as soon as possible. Whitening can not only prevent diseases and insects, but also reflect light, delay the temperature rise of the tree body and delay the flowering period. Whitening agent formula:0.25 kg of lime-sulfur mixture stock solution, 0.25 kg of table salt, 1.5 kg of quicklime, a little animal and vegetable oil, and 5 kg of water. Preparation method:slake quicklime with water, add grease and stir, add water to make lime milk, then pour the lime sulfur mixture and brine, stir well and serve; (3) spray chemical substances. For example, spraying 250-500 mg/kg of potassium naphthaleneacetate on the whole tree before germination can delay germination; spraying 150-400 mg/kg of abscisic acid solution or 0.5%calcium chloride at the early stage of germination can delay flowering; cover. Covering the tree with grass 20-30 cm can slow down the temperature of the soil and delay flowering. If it can be combined with irrigation, the effect will be better.
3. Spray antifreeze
2 to 3 days before the frost, spray antifreeze on the tree, such as 0.3%potassium dihydrogen phosphate + 0.3%urea, or use canola The lactones and amino acid solutions can lower the freezing point and enhance resistance.
4. Orchard smoke
Pay close attention to disaster weather information. Before the frost, use sawdust, wheat bran, broken straw, or orchard weeds and leaves to pile up alternately as fuel, and then press it up after stacking. Thin soil layer or use smoke generator to ignite smoke; or build antifreeze cellar in orchard, 5-8 per mu; or use anti-frost aerosol (3 parts ammonium nitrate, 5 parts sawdust, 1 part waste diesel, 1 part fine Coal). According to the weather forecast, the smoke pile is placed in the upper air vent of the orchard. Generally, 4-6 piles are piled per mu (the size and number of the piles depend on the intensity and duration of the frost). Pay close attention to temperature changes at night, when the temperature in the garden drops to -2.5℃, flowering period -1.0℃, young fruit The smoke will be ignited at -0.5℃.
5. Blowing convection
In areas prone to radiant frost, install high-power blowers above the orchard to agitate the air, enhance air circulation, and disperse the condensed cold air, which can prevent frost effect.
(Ma Fengwang, College of Horticulture, Northwest A&F University)