Ensuring Oilseed Rape Overwinters Safely: Strong Seedlings and Frost Protection Are Key

As oilseed rape now enters the overwintering period, the following field management measures should be carried out around strong seedlings and frost protection.

Fertilizing According to Seedling Condition:Seedling fertilizer is very important for oilseed rape to improve seedling quality and enhance frost resistance. For fields with sufficient basal fertilizer and vigorous growth at transplanting, fertilizer may be omitted; for fields with steady growth, apply less. However, for late-sown and late-transplanted fields without sufficient basal fertilizer, and for fields with currently poor growth of weak small seedlings or stiff seedlings (with only about 3 leaves and thin stems with red leaves) or uneven growth, fertilizer should be applied early as a supplemental dressing. Fertilization should be based mainly on organic fertilizer; for fields with thin, weak plants, an additional 5-10 kg of urea per mu may be applied to promote seedling recovery and strive for strong seedlings through the winter.

Clearing Ditches and Improving Drainage:Waterlogging damage is an important obstacle to high oilseed rape yields. For fields without ditches, seize favorable opportunities to promptly open ditches both inside and outside the field to improve drainage and reduce waterlogging, avoiding alternating freeze-thaw cycles that worsen frost damage. For fields with ditches that are not fully connected, deepen and clear them, especially adding horizontal and vertical ditches, connecting ditch heads, and keeping the ditch system unobstructed to ensure smooth drainage, so that fields dry after rain stops and severe waterlogging caused by continuous rainy weather in winter and spring is prevented. When opening and clearing ditches, the ditch soil should be evenly placed over the roots of the oilseed rape, especially burying the root crown of "tall-legged seedlings" into the soil, avoiding burying seedlings and causing missing plants.

Seizing Warm Weather for Weed Control:For fields where weed infestation reaches the threshold, seize the favorable opportunity of clear, warm weather with high temperatures, select the right herbicide and carry out chemical control as early as possible. Generally, when grass weeds exceed 50 plants per square chi and broadleaf weeds exceed 10 plants per square chi, chemical control must be carried out; apply on sunny days when the daily average temperature is above 5°C to improve herbicidal efficacy and avoid phytotoxicity. For grass weeds in oilseed rape fields, herbicides such as haloxyfop-R-methyl or quizalofop-p-ethyl may be selected; for broadleaf weeds such as cleavers (Galium aparine) and aquatic malachium (Malachium aquaticum), benazolin may be selected; for fields with mixed monocotyledonous and dicotyledonous weeds, the above herbicides may be mixed or their mixed formulations selected, or manual pulling may be combined with intertillage in winter and spring.

Mulching for Frost Protection:For no-till transplanted oilseed rape, carry out loosening of the soil and ridging around the roots in winter and spring to protect the roots, preserve warmth and prevent freezing. Use straw mulching to combine straw return with winter mulching of oilseed rape fields; generally, 150-200 kg of rice straw per mu is evenly spread to enhance the cold tolerance of oilseed rape. For vigorous growing seedlings of early-sown and early-transplanted oilseed rape that were not treated with paclobutrazol at the 3-leaf stage, before overwintering, on a clear warm day, spray 60-70 g of 15% paclobutrazol wettable powder per mu diluted with 30-50 kg of water to achieve dwarfing, greening and frost protection. Zuo Hailin