What are the measures for overwintering rapeseed to prevent freezing and protect seedlings
Measures for preventing freezing and protecting seedlings in overwintering rapeseed
Rapeseed is an autumn-sown crop and has a certain ability to withstand severe cold, but due to cold air invasions during the overwintering period, unscientific selection of varieties, late sowing or transplanting dates, improper application of fertilizer management measures, and other reasons, rapeseed frost damage is often caused, resulting in yield reductions of varying degrees, or even total crop failure. Therefore, measures to prevent freezing and protect seedlings should be taken promptly.
Apply heavy la fertilizer As the agricultural proverb says: "A thousand irrigations, ten thousand irrigations, are not as good as one application of la fertilizer." This fully demonstrates the role of applying la fertilizer to rapeseed. The appropriate time for applying la fertilizer is 10~15 days before the "Winter Solstice." Generally, apply 1200~1500 kg of pig and cattle manure per mu, or 2500~3000 kg of farmyard manure, which can raise the soil temperature by 2°C~3°C and produce the effect of winter application and spring growth.
Intertillage and earthing up, clearing ditches and draining water Intertillage and loosening the soil, and earthing up around the roots, can improve the soil environment of the rapeseed field, regulate soil moisture, raise soil temperature, and also prevent lodging and reduce the harm of weeds and sclerotinia. The depth of intertillage should vary according to the different growth conditions of rapeseed. Generally, it should be shallow first and then deep. For plots with vigorous growth, deep hoeing is suitable; for plots with weak growth, shallow hoeing is suitable. Before overwintering, combine intertillage with earthing up around the roots.
Topdress with dilute manure water Before the soil freezes, splash-apply 600~800 kg of clear manure water per mu, which can increase the concentration of the soil solution and make the soil less likely to freeze, thereby reducing root frost damage.
Foliar fertilizer spraying During the overwintering period, spray potassium dihydrogen phosphate, vitality essence, and Huimanfeng solution. For boron-deficient rapeseed, spray a 0.2% borax solution, which is beneficial for preventing freezing and protecting seedlings.
Increase mulch cover Before winter, cover rapeseed seedlings with farmyard manure, plant ash, crop straw, and other materials. This can keep soil temperature relatively stable, reduce leaf transpiration, avoid direct damage to leaves from cold air, and also fill soil cracks to prevent wind leakage and seedling suspension. For example, covering with rice straw at 200~300 kg per mu both preserves moisture and prevents freezing, while also increasing soil organic matter. The rice straw spread on the bed surface can naturally settle when rain falls, and generally does not affect the photosynthesis of rapeseed.
Spray paclobutrazol For rapeseed plots that were sown or transplanted early, have vigorous growth, and tend to grow excessively, spraying paclobutrazol solution around December 20 can make the plants stocky, turn the leaf color green, and prevent or reduce frost damage. Spraying method: use 50~60 g of 15% paclobutrazol wettable powder per mu, dilute with 60 kg of water, and spray evenly on the leaves, taking care not to miss any area or spray twice.
Irrigation to prevent freezing Irrigating the rapeseed field once before a cold wave arrives can stabilize soil temperature, supply water to the seedlings during the overwintering period, and effectively prevent dry freezing; irrigation after freezing should be carried out at noon on a clear day at the end of a cold spell and the beginning of warmth, so that the frozen and raised surface layer settles down, ensuring close contact between the rapeseed roots and the soil, which is beneficial for preserving seedlings and stabilizing roots.
Disease and pest control Timely control of rapeseed aphids, cabbage caterpillars, and flea beetles is beneficial for vigorous seedling growth. Generally, use 10~15 g of 10% imidacloprid diluted with water for spraying; alternatively, use 100 mL of 40% omethoate and 20 mL of 2.5% deltamethrin, diluted with 150 kg of water for spraying. Note that spraying must be done after thawing to prevent leaf damage and phytotoxicity. For rapeseed fields with severe damping-off and rust, carbendazim or thiophanate-methyl can be used for control.
Control early bolting When rapeseed bolts early, not only is more nutrients consumed, but its cold resistance is also weak, making it susceptible to frost damage. For plots showing signs of early bolting and early flowering, carry out deep intertillage to damage part of the root system, which can delay the occurrence of early bolting and early flowering; for rapeseed that has already bolted and flowered early, after the Spring Festival choose a clear day with relatively high temperatures to remove the bolts, and promptly topdress with quick-acting nitrogen fertilizer to promote plant recovery and reduce frost damage losses.
Post-freezing remediation After the cold wave passes, promptly inspect the seedlings. For rapeseed that has been lifted out of the soil, promptly break up the soil and earth up around the base by 8~10 cm to prevent root breakage and seedling death; in rainy and snowy weather, drain field water early to avoid waterlogging hindering root growth; when thawing, spread plant ash or burned soil ash, and promptly spray the leaves with clear water to alleviate water imbalance and prevent dehydration and seedling death; after thawing, promptly topdress with quick-acting fertilizer to promote branching and increase fruit-bearing positions; for bolting buds with split main stems and severely frozen leaves, remove them promptly.
Apply heavy la fertilizer As the agricultural proverb says: "A thousand irrigations, ten thousand irrigations, are not as good as one application of la fertilizer." This fully demonstrates the role of applying la fertilizer to rapeseed. The appropriate time for applying la fertilizer is 10~15 days before the "Winter Solstice." Generally, apply 1200~1500 kg of pig and cattle manure per mu, or 2500~3000 kg of farmyard manure, which can raise the soil temperature by 2°C~3°C and produce the effect of winter application and spring growth.
Intertillage and earthing up, clearing ditches and draining water Intertillage and loosening the soil, and earthing up around the roots, can improve the soil environment of the rapeseed field, regulate soil moisture, raise soil temperature, and also prevent lodging and reduce the harm of weeds and sclerotinia. The depth of intertillage should vary according to the different growth conditions of rapeseed. Generally, it should be shallow first and then deep. For plots with vigorous growth, deep hoeing is suitable; for plots with weak growth, shallow hoeing is suitable. Before overwintering, combine intertillage with earthing up around the roots.
Topdress with dilute manure water Before the soil freezes, splash-apply 600~800 kg of clear manure water per mu, which can increase the concentration of the soil solution and make the soil less likely to freeze, thereby reducing root frost damage.
Foliar fertilizer spraying During the overwintering period, spray potassium dihydrogen phosphate, vitality essence, and Huimanfeng solution. For boron-deficient rapeseed, spray a 0.2% borax solution, which is beneficial for preventing freezing and protecting seedlings.
Increase mulch cover Before winter, cover rapeseed seedlings with farmyard manure, plant ash, crop straw, and other materials. This can keep soil temperature relatively stable, reduce leaf transpiration, avoid direct damage to leaves from cold air, and also fill soil cracks to prevent wind leakage and seedling suspension. For example, covering with rice straw at 200~300 kg per mu both preserves moisture and prevents freezing, while also increasing soil organic matter. The rice straw spread on the bed surface can naturally settle when rain falls, and generally does not affect the photosynthesis of rapeseed.
Spray paclobutrazol For rapeseed plots that were sown or transplanted early, have vigorous growth, and tend to grow excessively, spraying paclobutrazol solution around December 20 can make the plants stocky, turn the leaf color green, and prevent or reduce frost damage. Spraying method: use 50~60 g of 15% paclobutrazol wettable powder per mu, dilute with 60 kg of water, and spray evenly on the leaves, taking care not to miss any area or spray twice.
Irrigation to prevent freezing Irrigating the rapeseed field once before a cold wave arrives can stabilize soil temperature, supply water to the seedlings during the overwintering period, and effectively prevent dry freezing; irrigation after freezing should be carried out at noon on a clear day at the end of a cold spell and the beginning of warmth, so that the frozen and raised surface layer settles down, ensuring close contact between the rapeseed roots and the soil, which is beneficial for preserving seedlings and stabilizing roots.
Disease and pest control Timely control of rapeseed aphids, cabbage caterpillars, and flea beetles is beneficial for vigorous seedling growth. Generally, use 10~15 g of 10% imidacloprid diluted with water for spraying; alternatively, use 100 mL of 40% omethoate and 20 mL of 2.5% deltamethrin, diluted with 150 kg of water for spraying. Note that spraying must be done after thawing to prevent leaf damage and phytotoxicity. For rapeseed fields with severe damping-off and rust, carbendazim or thiophanate-methyl can be used for control.
Control early bolting When rapeseed bolts early, not only is more nutrients consumed, but its cold resistance is also weak, making it susceptible to frost damage. For plots showing signs of early bolting and early flowering, carry out deep intertillage to damage part of the root system, which can delay the occurrence of early bolting and early flowering; for rapeseed that has already bolted and flowered early, after the Spring Festival choose a clear day with relatively high temperatures to remove the bolts, and promptly topdress with quick-acting nitrogen fertilizer to promote plant recovery and reduce frost damage losses.
Post-freezing remediation After the cold wave passes, promptly inspect the seedlings. For rapeseed that has been lifted out of the soil, promptly break up the soil and earth up around the base by 8~10 cm to prevent root breakage and seedling death; in rainy and snowy weather, drain field water early to avoid waterlogging hindering root growth; when thawing, spread plant ash or burned soil ash, and promptly spray the leaves with clear water to alleviate water imbalance and prevent dehydration and seedling death; after thawing, promptly topdress with quick-acting fertilizer to promote branching and increase fruit-bearing positions; for bolting buds with split main stems and severely frozen leaves, remove them promptly.