Detailed Explanation of Rapeseed Cultivation Techniques: Key Cultivation Points and Field Management Methods
Raising Strong Seedlings
1. Select good varieties: According to the local cultivation system and climatic conditions, combined with the local soil fertility level and production situation, choose varieties with strong stress resistance and good yield performance.
2. Prepare the seedbed well: The seedbed should be selected in a ventilated and sunny location, with fertile and loose soil, close to a water source, and finely prepared. Seedbed preparation should achieve "level", "fine", and "firm".
3. Sow at the right time: Rapeseed is very sensitive to sowing date. Therefore, determining the sowing date is an important issue in rapeseed cultivation. Rapeseed germination, emergence, rooting, and leaf growth all require certain temperature conditions. The optimum temperature for germination requires a daily average temperature of 16-22°C, and seedling leaf development also requires above 10-15°C to proceed smoothly. In addition, it is necessary to ensure at least 40-50 days of effective growth period after transplanting before entering overwintering.
4. Seedbed management: The day before transplanting, water thoroughly with "lifting water" to facilitate pulling seedlings and reduce root damage. In fertilizer management, grasp the principle of "promote early, control midway, stabilize late". On the basis of applying sufficient base fertilizer before sowing, at the three-leaf stage combined with thinning, topdress seedling fertilizer well. Generally, apply 20-30 loads of clear water manure or 2-3 kg of urea per mu to promote leaf opening and seedling development. 5-6 days before transplanting, apply 7.5 kg of urea per mu as lifting fertilizer, which is beneficial for early seedling growth after planting. Timely control pests and diseases. Aphids and cabbage caterpillars are the main pests in rapeseed seedling fields. Use pesticides in a timely manner for control. At the same time, clear weeds around the seedbed to reduce pest sources. 3-4 days before transplanting, apply a comprehensive "lifting pesticide" once to prevent pests from being brought into the field.
Timely Transplanting
1. Apply sufficient base fertilizer: Rapeseed plants are tall and require a large amount of fertilizer, so attention should be paid to the application of base fertilizer. Insufficient base fertilizer leads to weak seedlings, which further affects plant growth and even the economic yield of rapeseed. Base fertilizer should be mainly organic fertilizer, supplemented by chemical fertilizer, to lay a good foundation for the fertilizer needs of rapeseed throughout its life. Generally, apply 2000 kg of organic fertilizer per mu, 25-30 kg of 45% general-purpose compound fertilizer or 30-40 kg of 36% compound fertilizer (15-10-11), and 0.5-1 kg of boron fertilizer. Application method: Combine with plowing and land preparation to deeply apply organic fertilizer, compound fertilizer, and boron fertilizer. Avoid applying fertilizer too shallow to prevent fertilizer deficiency in the middle and late stages of rapeseed.
2. Transplant at the right time: Reasonable close planting. When the seedling age is 30-35 days, with 5-6 green leaves and root diameter of 5-6 mm, transplant large strong seedlings with soil, fertilizer, and pesticide. Do not transplant tall seedlings, curved-foot seedlings, or thin and diseased seedlings. Transplanting specification is 50 cm × 20 cm, with about 7000 plants per mu. Transplant while covering soil, and water thoroughly with root-setting water promptly after transplanting. 3 days after transplanting rapeseed, check for gaps and fill missing seedlings.
Reasonable Topdressing
1. Seedling fertilizer: Apply seedling fertilizer early and frequently to timely supply the nutrients needed during the rapeseed seedling stage, utilize the brief higher temperatures before winter to promote rapeseed growth, achieve strong seedlings for overwintering, and lay the foundation for high and stable rapeseed yield. Seedling fertilizer can be divided into two topdressings: early seedling stage and late seedling stage. Early seedling fertilizer is applied at thinning or at the 5 true-leaf stage, generally 5-6 kg of urea per mu. In soils deficient in phosphorus and potassium, if base fertilizer did not include phosphorus and potassium fertilizer, supplement with phosphorus and potassium fertilizer. Late seedling topdressing should depend on seedling condition and climate. Generally, apply 8-10 kg of high-nitrogen compound fertilizer per mu. Varieties with strong springness or areas with warmer winters should apply early; areas with low winter temperatures or triple-cropping rapeseed areas may apply appropriately later.
2. Bolting fertilizer: The bolting stage of rapeseed is a period when vegetative growth and reproductive growth proceed together. Plants rapidly bolt, grow branches, leaf area increases, and flower buds differentiate in large numbers. This is the period of greatest fertilizer demand and the key period for increasing branches and pods. Therefore, stably apply bolting fertilizer as appropriate according to the application of base fertilizer and seedling fertilizer and the growth condition. If base and seedling fertilizers are sufficient and plants grow robustly, apply less or none; if base and seedling fertilizers are insufficient and there is a trend of fertilizer deficiency, apply bolting fertilizer early. Generally, apply 15-20 kg of high-nitrogen compound fertilizer per mu. The fertilization time is generally at the middle bolting stage, with a bolting height of 15-30 cm. However, weak-growing plants can be fertilized at the early bolting stage to avoid premature senescence; strong-growing plants can be topdressed at the late bolting stage when the bolting height is 30-50 cm, to avoid excessive growth at flowering causing closure.
3. Flower fertilizer: After rapeseed bolts, it flowers while forming pods. The number and weight of seeds are closely related to the nutritional conditions after flowering. For vigorous growth with a large amount of fertilizer applied at the bolting stage, it may not be applied or applied less; for early-maturing varieties, do not apply, or apply less at the initial flowering stage. Flowering topdressing can be applied by foliar spraying. During the flowering and pod-setting period, spray 0.1-0.2% urea or 0.2% potassium dihydrogen phosphate. In addition, spray 0.2% borax aqueous solution once each at the late seedling stage and bolting stage to prevent the phenomenon of "flowers but no seeds" and increase yield.
Irrigation and Drainage
Reasonable irrigation and drainage are important measures to ensure high and stable rapeseed yield. Rapeseed has a long growth period, large vegetative mass, luxuriant plant leaves, and many fruiting organs, requiring a relatively large amount of water throughout its life. Rapeseed production areas generally have less rainfall in autumn, winter, and spring, and soil drought, which is not conducive to sowing, emergence, and raising strong seedlings. In northern regions, winter drought often aggravates freeze damage and causes seedling death. In southern regions, excessive rainfall in the later period causes waterlogging or flooding damage. Therefore, it is necessary to irrigate and drain promptly according to local conditions based on the water requirements of rapeseed.