Wheat frost falls below 0°C in the ground and falls below the minimum temperature that wheat can withstand in a certain developmental stage, causing wheat to suffer freezing injury. After the jointing of wheat, the cold-resistance ability gradually weakens, and it is vulnerable to frost damage. From the external shape of the plants, some of the wheat damaged by frost may be damaged by the stem, some may turn yellow and twisted, and the plants may wither. They may also cause the male and female of the panicle. The core is frozen and the floret is degraded. The seed setting rate is reduced and the yield is affected. Therefore, to strengthen forecasting and defense, common defense methods are as follows:
Irrigation-irrigation The role of frost protection: The first is the water temperature of the irrigation, which is higher than the soil temperature when the frost occurs, and sometimes higher than 10°C. Therefore, irrigation before frost can bring a lot of heat; Secondly, the water content of the soil after irrigation The increased capacity can make the heat in the lower layer of the soil come up. Third, because the volume of water is much larger than that of air and soil, the temperature of the ground can be reduced after the irrigation to avoid sudden heat and cold; Fourth, after the water is poured, the air in the near-surface layer Increased moisture, latent heat during condensation. In areas with sprinkling conditions, spraying water in the event of frost and adjusting the microclimate in the field are very effective in preventing frost. According to the investigation, after irrigating, the ground temperature can be increased by 1°C-3°C, the maximum is 4.1°C, and the temperature of the foliage is increased by 0.2°C-0.7°C. The frost damage is significantly reduced.
Smoke - There is a long history of application of firewood smoke protection cream. In areas with insufficient fuel, CHN chemical smokers can be used. The agent is a mixture of ammonium nitrate, residual oil and sawdust. The main principle of frost protection is that, first, the smoke forms a smoke curtain when it burns, and attracts radiant heat inside the smoke, which can reduce radiation cooling on the ground and prevent a large amount of heat loss from the soil and plants. Second, the smoke releases heat when it burns, and can make The temperature rises; thirdly, when the water vapor condenses on the smoke, the latent heat is released, which can also increase the temperature.
The time for smoking must be mastered. It should not be too early or too late. Generally, when the temperature of the leaf surface drops to 1°C higher than the frost index, it is necessary to publish the cigarette lightening time and ensure the quality, so as to obtain good results. The frost-tolerant varieties are often used in frost-prone areas. Therefore, it is necessary to select and match the cold-tolerant varieties that are planted late in the festival. Because the early jointing varieties are susceptible to freezing damage, the late jointing varieties come in the form of late frosts and show strong cold resistance and light freezing injury.
Strengthen cultivation and management, improve wheat antifreeze ability (1) timely sowing. The early planting began early jointing and was prone to frost damage. (2) Implementation of repression before jointing can inhibit the growth of roots, promote root development, and reduce the effects of frost. (3) Based on the situation of the seedlings, based on antifreeze and reasonable fertilization. Excessive application of nitrogen fertilizer plants prosperous, susceptible to frost damage, and more phosphorus and potassium fertilizers, can increase frost resistance, have a significant effect on defense frost. (4) Foliage sprayed with chlormequat and paclobutrazol at the jointing stage can inhibit plant growth and reduce plant height, and it can both prevent and freeze.
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