Prevention of Freezing Injury of Rape by "Spraying from Lower to Upper"

Rape is an overwintering crop, and freezing injury is easy to occur if varieties are not selected properly, sowing and planting are too late, improper fertilization and so on. In order to prevent the freezing injury of rape, in addition to selecting cold-resistant and cold-resistant varieties, sowing in time, cultivating strong seedlings and transplanting, the following technical measures should be taken: increasing the application of phosphorus, potassium fertilizer and phosphorus can promote the root development of rape and enhance the resistance of rape. Potassium can improve the ability of cold resistance, disease resistance and lodging resistance of rape. Therefore, in the process of topdressing fertilizer, the amount of nitrogen fertilizer should be properly controlled or reduced to avoid tender and succulent plants and poor cold resistance. Heavy application of wax fertilizer farmer proverb said: "thousands of watering, better than wax fertilizer watering." This fully shows the role of rape application of wax fertilizer. The application time of wax fertilizer is suitable for the first 10-15 days of "the Winter Solstice". Generally, the application of pig and cow manure 1200-1500 kg per mu or soil and miscellaneous fertilizer 2500-3000 kg per mu can increase the soil temperature by 2-3 ℃, effectively reduce the damage caused by soil freezing in the plough layer, and have the effect of winter application and spring application. Adding mulch to cover rape seedlings with soil fertilizer, plant ash and crop straw before winter can keep the ground temperature relatively stable, reduce leaf transpiration, avoid direct damage to leaves by cold air, close soil seams and prevent air leakage from hanging seedlings. If covered with straw, 200 kilograms per mu, it not only preserves soil moisture and frost, but also increases soil organic matter. The straw covered on the border can be carried out naturally in the event of rainfall, and generally does not affect the photosynthesis of rape. Spraying paclobutrazol on rape plots with early sowing, vigorous growth and overgrowth trend, spraying paclobutrazol solution around December 20 can make the plant firm, the leaf color turn green, and prevent or reduce freezing injury. Spraying method: use 15% paclobutrazol wettable powder 50 grams per mu, spray leaves evenly to 60 kilograms of water, pay attention to no leakage spray, do not re-spray. Spraying foliar fertilizer on rape before winter, the key is to spray phosphorus and potassium fertilizer, which can increase the concentration of cell sap, reduce the freezing point and enhance the ability of cold resistance. During the overwintering period, potassium dihydrogen phosphate, activating element and Huimanfeng solution were sprayed, and 0.2% borax solution was sprayed on boron-deficient rape, which was beneficial to anti-freezing and seedling protection. The control of early bolting of rapeseed not only consumes more nutrients, but also has weak cold resistance. For the plots with signs of early bolting and early flowering, deep ploughing and damaging part of the roots can delay the occurrence of early bolting and early flowering; rape with early bolting and early flowering can choose to pick bolts in sunny days and high temperatures after the Spring Festival, and apply available nitrogen fertilizer in time to promote plant recovery and reduce the loss of freezing injury.