Detailed Explanation of Key Techniques for High-Yield Rapeseed Cultivation
Rapeseed (Brassica napus) is an annual herbaceous plant with a taproot system, an upright stem, relatively few branches, and a plant height of 30-2250px. Rapeseed is an edible crop with strong cold resistance. The minimum temperature for rapeseed seed germination is between 4-6°C. It prefers cool conditions; rapeseed grown in areas with large day-night temperature differences is more likely to flower and produce mature siliques, and to accumulate more dry matter and oil. Before flowering, rapeseed is green, with only a few green leaves, thick stems and thin leaves; during the vigorous flowering period, the flowers are small, golden-yellow and tender, with great ornamental value. For this reason, some scenic rural areas specifically plant rapeseed flowers so that during the blooming season they can serve as scenic spots for tourists to admire. After the flowers fade, purple-brown long siliques are produced that are 3-200px long, 2-3mm wide, with a 9-24mm beak at the tip. They can be planted and can be pressed for oil. According to measurements, for every 100 kg of rapeseed produced, the required ratio of nitrogen, phosphorus and potassium is 1:0.35:0.95, which is more than 3 times the requirement of general cereal crops. In addition, rapeseed is relatively sensitive to the trace element boron, and deficiency can easily cause flowers but no seed set.
1. Selection of improved varieties
The rapeseed varieties currently grown in China mainly include three types: pak choi-type rapeseed, mustard-type rapeseed, and cabbage-type rapeseed. When the soil conditions, meteorological conditions and other factors of the planting area are clearly understood, a rapeseed variety suitable for cultivation in that area should be selected; otherwise, varieties with high quality, disease resistance, high yield and bolting tolerance should be given priority, such as Huaguan and Jinglv No. 2.
2. Planting methods
Rapeseed cultivation includes two methods: direct sowing and seedling raising followed by transplanting. In China, when the rapeseed planting area is relatively large, direct sowing is generally used; when the planting area is relatively small, seedling raising followed by transplanting is generally used. In addition, because rapeseed seeds are small, with 1000 seeds weighing only 2.5g-4g, in order to maximize the success rate of planting, different row spacings should be selected for planting according to the intended use of the rapeseed being grown. For example, for green fodder use, a row spacing of 2.5-1000px and a sowing rate of 0.3-0.4kg per mu are used; if used for oil pressing, the row spacing should be increased and the sowing rate reduced to improve rapeseed yield. For rapeseed grown by seedling raising, a seedbed should first be prepared and the land planned properly. On the premise that fertilizer and irrigation measures are ready, rapeseed seeds are broadcast on the seedbed; when the seedlings grow 1-2 true leaves, they are removed to cultivated land for secondary planting.
It is very important to sow at the appropriate time, because sowing too late will lead to delayed market availability and problems such as poor product quality caused by missing the optimal sowing time, ultimately adversely affecting the economic income of the growing unit.
3. Cultivation stage
During the growth period of rapeseed, protective work such as fertilization, irrigation and pest control must be carried out to promote the vigorous growth of rapeseed seeds or transplanted seedlings. For example, in the Chongqing area, during the cultivation stage of rapeseed, it is necessary to ensure sufficient and appropriate moisture. On the day of transplanting, root-setting fertilizer water should be applied; 20 days after transplanting, the first topdressing should be applied; in early December, a heavy application of the opening fertilizer should be made. In the field, 2000kg of farmyard manure, 10kg of urea, 40kg of superphosphate, 10kg of potassium chloride and 1kg of borax should be applied per mu (in arid areas or dry years, boron fertilizer should be applied to the leaves at the early flowering stage). When growing rapeseed in the north, in addition to the above-mentioned fertilization and irrigation, cold and freeze protection measures for rapeseed in winter must also be taken. In addition to insulating with plastic greenhouses, fertilizers containing multiple elements such as nitrogen, phosphorus, potassium and boron required for rapeseed growth should also be applied.
Second, for some rapeseed flower fields mainly used for ornamental purposes, attention should be paid to maintaining the flower fields in the early flowering period to avoid incidents such as some tourists trampling the flower fields and picking the rapeseed flowers. Once this happens, it will seriously affect the growth of rapeseed flowers and prevent them from reaching their most vigorous flowering period.
Moreover, the cultivation period of rapeseed, that is, the growth period of rapeseed, is the most critical period for increasing oil yield. The effectiveness of technical maintenance work carried out at this stage will directly affect the final yield of the entire year.
4. Harvest
Mastering the optimal harvest time for rapeseed is also one of the important technical methods for high rapeseed yield. During the silique maturation period, attention should be paid to controlling aphids and preventing bird damage to prevent rapeseed growth from being affected.
Generally, rapeseed can be harvested when a small portion of the siliques turn yellow. If harvesting is delayed until half or more of the siliques turn yellow, that is, when the silique hulls of the rapeseed seeds turn yellow, the best harvest time has already been missed, because the rapeseed seeds harvested at this time are already mature; if harvesting is delayed until the rapeseed is completely mature, even greater economic losses will be caused. Therefore, constant attention should be paid to the growth changes of rapeseed, preparations for harvest should be made in advance, and harvesting should be carried out when the effective yield of rapeseed is at its highest.
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