Measures to prevent freezing and protect seedlings of overwintering rape

Rape is an autumn sowing crop, which has a certain ability to resist severe cold, but it often causes freezing injury of rape due to the invasion of cold air during overwintering, unscientific selection of varieties, late sowing date, improper application of fertilization management measures and so on. resulting in varying degrees of yield reduction, or even no harvest. Therefore, measures should be taken to prevent freezing and protect seedlings in time.

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 suitable application time of wax fertilizer is the first 10-15 days of "the Winter Solstice". Generally, the application of pig and cow manure 1200-1500 kg per mu or soil fertilizer 2500-3000 kg per mu can increase the soil temperature by 2 ℃ ~ 3 ℃, which has the effect of applying in winter and spring.

Ploughing and cultivating soil, clearing trenches and draining water, ploughing and loosening soil, and cultivating soil choking roots can improve the soil environment of rape field, regulate soil moisture, increase soil temperature, prevent lodging and reduce the harm of grass damage and Sclerotinia sclerotiorum. The depth of mid-tillage should vary according to the growth of rape, generally shallow first and then deep, deep hoe for prosperous land and shallow hoe for weak land, and combine ploughing to cultivate soil before overwintering.

Before applying thin dung water before freezing, 600 kg of clear manure water per mu can increase the concentration of soil solution and make the soil not easy to freeze, so as to reduce the freezing of roots.

Foliar fertilizer was sprayed with potassium dihydrogen phosphate, activating element and Huimanfeng solution during overwintering, and 0.2% borax solution was sprayed on boron-deficient rape, which was beneficial to anti-freezing and seedling protection.

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.

Irrigation of the anti-freezing rape field once before the cold current can stabilize the ground temperature, supply water to the seedlings during the overwintering period, and effectively prevent dry freezing; post-freezing irrigation should be carried out at noon on a sunny day with a cold tail and a warm head, so as to make the frozen protruding surface layer sink, and ensure that the rape roots are in close contact with the soil, which is conducive to keeping the seedlings stable.

Timely control of rape aphids, cabbage green beetles and jumping beetles is conducive to the robust growth of rape seedlings. 10% imidacloprid is generally used to spray 15 grams of water; 40% omethoate 100 ml and 2.5% enemy can be used to kill 20 ml and spray 150 kg of water. Note that the spray must be carried out after thawing to prevent damage to the leaves and cause drug damage. Carbendazim or methyl topiramate can be used to control rape fields with severe quenching and rust.

Controlling the occurrence of early bolting of early bolting rape not only consumes more nutrients, but also has weak cold resistance and is vulnerable to freezing injury. 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.

After the cold current is remedied after freezing, the seedlings should be checked in time. For rape with root uprooting, it is necessary to break the soil and cultivate 8cm in time to prevent root loss and death; to eliminate stagnant water in the field as early as possible in rainy and snowy weather to avoid waterlogging hindering root growth; to spread plant ash or fire soil ash during thawing, and to spray clear water on the leaves in time, so as to alleviate water imbalance and prevent water loss and death of seedlings. After thawing, quick-acting fertilizer should be applied in time to promote branching and increase the position of fruit, and the broken bolting buds of the main stem and severely frozen leaves should be removed in time.