Spring freezing injury refers to the frost damage caused by the onset of cold wave during the period of returning to the jointing stage. According to the occurrence of frost damage, it can be divided into early and late winter frost damage and late spring and late frost frost damage. Early spring frost damage occurs more frequently and to a greater extent. It mostly occurs in late February to March; Late frost damage occurs in late spring and early April. Therefore, when the temperature has gradually warmed, and suddenly encountered a cold wave, so often frost frost damage is also known as "cold spring." In recent years, with the change of variety, the freezing injury of wheat in spring has become an important factor limiting the yield, and sometimes worse than the winter freezing injury. Therefore, it is one of the important measures for the management of spring wheat in the spring to do a good report of frost damage in spring and take corresponding measures to prevent or remedy it. Since the wheat panicle has already completed the development of the vernalization and illumination stages, the ability of the wheat to resist cold during the vernalization stage has been significantly reduced. After the light stage, jointing begins and the ability to withstand low temperatures below 0°C is completely lost. When the cold wave arrives, it is clear and windless at night. When the surface temperature suddenly drops below 0°C, spring frost damage will occur. Agro-ecological measures and chemical regulation can be used to prevent the occurrence of frost damage in spring.
1. Irrigation anti-frost
Since the heat capacity of water is larger than the heat capacity of air and soil, irrigation can increase the water vapor in the air near the ground. When condensation occurs, latent heat is released and the temperature of the ground can be buffered. At the same time, soil moisture increases after irrigation, the soil thermal conductivity increases, and the soil temperature increases. According to the survey, irrigation before frost can increase the temperature of the wheat field near the ground 2 ~ 4 °C, with the role of reducing frost damage. Therefore, to prevent frost damage, according to the weather forecast, the wheat field can be irrigated with small water 1 to 2 days before the beginning of frost and the arrival of late spring (where sprinkler irrigation is recommended). Generally, sand and highland should be poured late, and clay ground and low-lying land should be poured in early. The soil moisture can be poured well.
2. Antifreeze crackdown
Repression can effectively regulate soil moisture, air and temperature and is an important agronomic measure for wheat cultivation. It can crush clods, break down soil, enhance soil capillary effect, increase the moisture in the lower layer, adjust the pores of the plough layer, seal the soil cracks, prevent cold air from invading the soil, increase the soil heat capacity and thermal conductivity, stabilize the ground temperature, and increase the cold and resistance of the wheat field. Freeze and drought resistance, reduce winter dead seedlings. When repressing, it should be combined with soil quality, lyricism, seedling conditions and weather. Saline-alkali land resilience can easily cause back-salt, deteriorate soil permeability, affect the growth of wheat seedlings, and cannot repress. The soil with heavy clay and hard-topped wheat fields should not be repressed to avoid excessive damage to the wheat seedlings. Leakage winds run through the wind and can be heavy pressure; the soil and sandy loam soil is ploughed well and should be lightly pressed; wind and sand soil running and hanging roots should be properly weighed. The poor quality of the soil preparation and the pressure of the soil to be aerated should be heavy; the good quality of the soil preparation can be lightly pressed. Poor soil moisture should be heavy pressure, good moisture can be light pressure, the soil can not be too wet. Generally, 0 to 10 cm of soil with soil moisture content up to 17% cannot be repressed so as not to cause compaction. Wang Miao control on the promotion of continuous pressure, strong seedlings to prevent root prone to discretion, pressure, weak seedlings should be light pressure on drought and freezing. Under normal circumstances weak seedlings do not repress, small seedlings can not be pressed, seedlings should not be heavy pressure, and can not be pressed after jointing. Spring repression takes place after thawing.
3. Chemical control antifreeze
Before the wheat comes up to frost damage during the jointing stage, spraying 20% ​​Zanthoxyl emulsifiable concentrate 30-40 ml per mu 30-40 kg or 0.3%-0.5% chlorcholine solution can inhibit plant growth and jointing speed and resist Or reduce the occurrence of frost damage.
4. Smoke protection and antifreeze
Pay close attention to the changes in the weather, before the arrival of the cold, in the evening in the field piled wheat stubble, straw and other smoke.
5. Remedial measures adopted after frost damage
After the occurrence of cold injury, timely adoption of agro-remedial measures such as cultivating, top-dressing, and irrigation will enable the wheat to resume its growth, and will exert its own regulatory ability, significantly reducing the loss of frost damage due to early planting of spring varieties, especially in time. N fertilizer and watering, catching 10 kg of urea per mu, effective guarantee of high spring tiller, reducing the deterioration of spikelets and small flowers, also has a significant effect on increasing grain number and grain weight.
In addition, the use of plant growth regulators can quickly restore wheat growth. Plant growth regulators such as sodium nitropruslate and diethylaminoalkanoate (DA-6) have a significant effect on the recovery of wheat after frostbite, which is manifested by the rapid growth of medium and small tillers and the rapid growth of latent shoots. , Significantly increase the spike number and 1000-grain weight of wheat, which can significantly increase wheat yield.
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