Apply seedling fertilizer early and frequently, supply the nutrients needed by rape seedlings in time, promote rape growth by using short-term high temperature before winter, realize strong seedlings overwintering, and lay the foundation for high and stable yield of rape. Seedling fertilizer can be divided into pre-seedling and post-seedling topdressing twice. Fertilizer before seedling should be applied when seedlings are fixed or 5 leaves are planted. Generally, 5-6 kilograms of urea is applied per mu. Phosphorus and potassium deficiency soil, base fertilizer without phosphorus and potassium fertilizer, phosphorus and potassium fertilizer should be supplemented. Topdressing at the later stage of seedling stage depends on seedling condition and climate. Generally, 8- 10 kg of high nitrogen compound fertilizer is applied per mu. Varieties with strong spring or areas with warm winter should be applied early, and areas with low winter temperature or triple cropping rape can be applied late.

2. Stable fertilization

The flowering period of rape is the stage of vegetative growth and reproductive growth at the same time. The plants are bolting quickly, branching grows, the leaf area increases, and a large number of flower buds differentiate. This is a period when more fertilizer is needed, and it is also a key period to increase branches and pods. Therefore, it is necessary to stabilize fertilization according to the application and growth of base fertilizer and seedling fertilizer. Base fertilizer and seedling fertilizer are sufficient, plants grow healthily, and chemical fertilizer can be applied less or not; If the base fertilizer and seedling fertilizer are insufficient, fertilizer should be applied as soon as possible if there is a trend of fertilizer removal. Generally, high-nitrogen compound fertilizer 15-20kg is applied per mu. Fertilization time is generally in the middle bolting stage, and the bolting height is 15-30 cm. However, the weak growth can be fertilized at the initial stage of bolting to avoid premature aging; Those with strong growth can be topdressing at the late bolting stage when the bolting height is 30-50 cm, so as to avoid flowering and canopy closure.

Step 3 Apply flower fertilizer skillfully

After bolting, rapeseed bears pods at the edge of flowering, and the number and weight of seeds are closely related to the nutritional conditions after flowering. For those who grow vigorously and have a large amount of fertilizer in the medium term, they can not apply or apply less; Not suitable for early-maturing varieties, or less application at the beginning of flowering; Topdressing can be sprayed on leaves at flowering stage, and 0. 1-0.2% urea or 0.2% potassium dihydrogen phosphate can be sprayed at flowering and pod setting stage. In addition, 0.2% borax aqueous solution can be sprayed once in the late seedling stage and bolting stage to prevent the phenomenon of "flowers without fruit" and improve the yield.