Detailed Explanation of Key Points on Rapeseed Seed Selection and Cultivation Techniques
Rapeseed, also called oil bok choy or bitter greens, is a plant of the Brassicaceae family and Brassica genus, native to our country. Its stem is dark green, and its stalks resemble those of bok choy. It is a variety of Brassicaceae bok choy, and its flowers are yellow. In agronomy, multiple species of plants whose seeds contain oil are collectively called rapeseed. At present, the main cultivated (varietal) types of rapeseed are: bok choy-type rapeseed, mustard-type rapeseed, and cabbage-type rapeseed.
Seed Selection for Rapeseed
For rapeseed seed selection, consideration should be given to whether the variety has characteristics such as cold resistance, drought resistance, and resistance to sclerotinia. The selection of rapeseed seeds can be divided into pure conventional rapeseed and hybrid rapeseed. The requirements for conventional rapeseed are: purity should not be lower than 98%, and germination rate should be higher than 92%; the requirements for hybrid rapeseed are: purity should be higher than 97%, and germination rate should also be higher than 85%. To establish an efficient rapeseed operation model, the corresponding rapeseed variety must first be selected according to the local specific soil and climate. In some areas with relatively harsh environments, more consideration should be given to environmental and climatic factors when selecting rapeseed seeds, and emphasis should be placed on selecting varieties that are more drought-resistant and cold-resistant. For example, when planting rapeseed in areas such as Inner Mongolia, Qinghai, and Gansu, this factor must be given more consideration. A specifically selectable variety is Qingza No. 5. This variety has an oil content as high as 45% and a yield per mu of up to 300 kg. It is a high-yield, high-quality spring rapeseed hybrid successfully developed in recent years, and it is very suitable for planting in high-altitude areas above 2000 m in our country, with relatively good drought resistance and cold resistance.
Specific Cultivation Techniques
For rapeseed planting, different regions adopt different planting techniques. Some regions, in order to achieve high land utilization, adopt multiple cropping techniques after wheat; other places plant only one season, using single-crop direct seeding with two rounds of planting techniques. However, these two planting techniques mainly differ in the early land preparation stage, and the rest is basically the same in terms of sowing, field management, and so on, so it will not be repeated here. Below, we will give detailed introductions to these two different planting techniques respectively.
Land Preparation Work
Land preparation work in single-crop direct seeding
Rapeseed planting is mainly carried out on irrigated land. In spring planting, special attention should be paid to the soil moisture condition of the field. If drought occurs, water should be applied first. Then the field should be finely prepared, specifically by loosening the soil, maintaining the air content in the soil, and achieving firm below and loose above. Only in this way can rapeseed seeds germinate and grow better. In fertilizer application, it is necessary to ensure that 1500-2000 kg of organic fertilizer per mu is applied as base fertilizer.
Land preparation work for multiple cropping after wheat
After wheat harvest, the land is relatively dry, and there are a large number of wheat stubble, and wheat straw also remains in the field. Before sowing rapeseed, the residual wheat straw in the field must first be cleared. Through manual plowing or machine plowing, the wheat stubble should be dealt with. Fields with poor soil moisture should be watered. Likewise, under the premise of ensuring high yield, base fertilizer should be added to the land, usually about 1000 kg of organic fertilizer is appropriate.
Sowing Work
After the land is prepared and ready, sowing should be carried out in a timely manner. The main sowing methods are machine sowing and manual broadcasting. When using machine sowing, the requirements for the land are not very strict. The soil can be left unloosened first and sown using a wheat layered seeder. The most suitable sowing depth is 2-3 cm. The amount of rapeseed used is generally about 1.5 kg per mu, and about 150,000 plants per mu can be preset. During sowing, diammonium phosphate should be added in layers as seed fertilizer, with the specific rate being 5 kg per mu.
When broadcasting by hand, the land conditions are first required to be relatively good, needing manual tending and good soil moisture. The soil should be loose. After manual broadcasting, diammonium phosphate should also be spread once, with the same rate as above.
Fertilization Work
In addition to adding base fertilizer to the land when preparing the field, scientific and reasonable fertilization work should also be continuously carried out during the rapeseed growth cycle. First, when the rapeseed in the field grows to 3-4 leaves and final thinning is done, urea should be added once in a single application, with the specific amount being 2.5 kg per mu. In addition, during the flowering period of rapeseed, fertilizer should also be added to prevent phenomena such as leaf yellowing and flower bud shedding. Specifically, 0.1 kg of monopotassium phosphate, 0.05 kg of boron fertilizer, and 15 kg of water should be evenly mixed and sprayed on the rapeseed leaves.
Specific Field Management Work
First, after sowing, if the rapeseed seeds have not germinated and there is relatively heavy rainfall, causing surface crusting on the planted ground, the crust should be broken in a timely manner to avoid affecting the normal germination and growth of rapeseed. After rapeseed emerges, attention should be paid to clearing weeds on the ground, because rapeseed seedlings are difficult to distinguish from weeds, so weed removal work must be patient and very careful. When the rapeseed grows to about 20 cm, watering and irrigation should be carried out in real time according to the land conditions. During irrigation, fertilizer should be applied in combination, generally using 5 kg of urea as topdressing.
Pest and Disease Control Work
Pest and disease control work is mainly divided into insect pests and diseases. Below we introduce them separately in detail:
Diseases:
The main disease of rapeseed is sclerotinia. This disease can occur from the seedling stage to the mature stage of rapeseed and mostly occurs at the stem base, forming elongated sunken lesions. This pathogen not only affects rapeseed yield, but also has a relatively large impact on rapeseed quality and oil yield. Specific control measures should focus mainly on agricultural control, with chemical control as a supplement. The specific content is: in agricultural crop rotation, prevention and control of the sclerotinia pathogen should be done well, high-quality rapeseed varieties with relatively strong resistance to the sclerotinia pathogen should be selected, and reasonable fertilization as well as soil and water irrigation should be done well. In terms of chemical control, mainly before sowing, a suspension seed coating agent should be used for coating. The specific specification is 1000 ml of a suspension seed coating agent with a concentration of 2.5% used to coat 100 kg of seeds. In addition, at the bud stage or early flowering stage, a 700-fold solution of 20% dimethachlon should be used for leaf spraying. The number of sprayings should be greater than or equal to three, with the specific situation determined according to local planting conditions.
Insect pests:
The main insect pests of rapeseed include diamondback moth, aphids, cabbage caterpillar, flea beetle, and so on. Individual regions have different insect pests, and control work can be carried out according to local actual conditions. First, in order to prevent and control insect pests, seed dressing should be carried out before rapeseed sowing. A 70% acetamiprid dispersible powder at 500 grams can be used to dress 100 kg of seeds. During the growth process after rapeseed germination, pesticide spraying should be carried out. Specifically, 500 ml of fenvalerate and 500 ml of acephate can be used, added to water to make a 1000-fold solution for spraying. According to the pest situation, the dosage can be appropriately increased.
Rapeseed “two preventions and one spraying”
The budding and flowering stage of rapeseed is a critical period for rapeseed grain formation and pest and disease control. Therefore, the favorable opportunity should be seized to carry out “two preventions and one spraying”, control the harm of rapeseed sclerotinia and aphids, spray boron fertilizer, and increase rapeseed yield.
1. Spraying time
Spray all day on cloudy days; on sunny days, spraying before 11 a.m. and after 15:00 in the afternoon gives good results. On breezy days, spray along the wind direction; on windy days, spraying is not suitable.
2. Control methods
1. Control of sclerotinia: at the bolting stage, use 100 grams of monopotassium phosphate per mu plus 100 grams of 50% carbendazim wettable powder or 40% dimethachlon wettable powder, mixed with 50 kg of water and sprayed once, spraying the whole field including plants and field ridges, then spray once each at the early flowering stage, full flowering stage, and pod-setting stage. At the same time, remove old, yellow, and diseased leaves from the middle and lower parts of the plants and take them out of the field.
2. Control of aphids: use 25-40 grams of 1.8% abamectin-imidacloprid per mu, or 10 grams of imidacloprid per mu, or 15-20 ml of deltamethrin. Additionally add 100 grams of 25% carbendazim wettable powder or 100-150 grams of 40% dimethachlon wettable powder, mix with 30-40 kg of water and spray to control both pests and diseases.
3. Spraying boron fertilizer: spray 100 grams of ordinary boron fertilizer per mu; for nutrient-deficient field plots, 200 grams of monopotassium phosphate can also be added, or 0.5-1 kg of urea can be added, mixed with 75 kg of water and sprayed evenly.
4. At the same time, clear ditches and manage soil moisture, dredge the “three ditches”, drain surface waterlogging and remove hidden waterlogging, and promote the normal growth of the rapeseed root system.