When to Plant Rapeseed? A Detailed Guide to Timing and Methods
Rapeseed has very strong vitality. It is a relatively cold-tolerant crop, so it is distributed in many parts of our country. Rapeseed tastes good and has high nutritional value, so it is very popular every year when it reaches the market. As the price of rapeseed keeps rising, many people want to grow it.
Rapeseed Planting Time and Methods
Planting time:
The suitable sowing period for rapeseed should take into account climate, cropping system, variety characteristics, pest and disease conditions, previous crop, and other factors. However, appropriately early sowing of winter-type and semi-winter-type varieties can make full use of the season and extend the vegetative growth period. This helps to bring out the variety's potential and strive for high yield. The sowing temperature is generally best at an average temperature of 20°C. The direct sowing time for rapeseed is roughly from late September to early-to-mid October, while the suitable time for raising seedlings and transplanting is from early-to-mid September to late September.
Planting methods:
1. Planting density: suitable planting density. The suitable planting density varies greatly under different conditions in different regions. In our county, the suitable density for cabbage-type rapeseed is 7000-8000 plants for large-plant types and 8000-12000 plants for small-plant types.
2. Planting pattern: the same planting density can be arranged using different planting patterns.
(1) Wide and narrow rows: planting alternating wide rows and narrow rows can solve the ventilation and light penetration problems of relatively high planting density, raise ground temperature and soil temperature, better coordinate individual and population growth, and facilitate topdressing and field management. Generally, wide rows are 1.4 chi and narrow rows are 1 chi.
(2) Narrow rows and narrow plant spacing: widening the row spacing and reducing the plant spacing (such as row spacing 1 chi, plant spacing 4-5 cun) can delay row closure. It reduces shading, helps ventilation and light penetration, and facilitates field management.
(3) Equal row and plant spacing: adopting a planting pattern with equal row spacing and plant spacing, used at low density, gives relatively uniform branch distribution and more branches and pods.
Growing Conditions for Rapeseed
1. Temperature. Rapeseed is a crop that prefers cool conditions and has relatively strong cold resistance. The minimum temperature for seed germination is 3-5°C. At 20-25°C, seedlings emerge in 3 days. The flowering stage is 14-18°C, and the pod development stage is 12-15°C, and a large day-night temperature difference is beneficial for flowering and pod development, increasing the accumulation of dry matter and oil.
2. Water. Rapeseed has a long growth period, a large vegetative body, and many pod-bearing organs, so it needs more water. The water requirements at each growth stage are: during the emergence stage, soil moisture should generally be maintained at about 65% of field capacity; from the bud and stem stage to the flowering stage, it is 75-85% of field capacity; during the pod development stage, it is 70-80% of field capacity.
3. Fertilizer. Rapeseed is a fertilizer-tolerant crop with strong fertilizer uptake capacity. Throughout the entire growth process, it needs to continuously absorb large amounts of nutrients such as nitrogen, phosphorus, and potassium from the soil. According to measurements, for every 100 kg of rapeseed produced, the ratio of nitrogen, phosphorus, and potassium is 1:0.35:0.95, and the demand for these three elements is more than 3 times that of cereal crops. Secondly, boron fertilizer is an indispensable trace element for the growth and development of rapeseed. After boron deficiency, flowers appear but no seeds set, that is, after rapeseed flowering, the young pods do not expand or do not set seed. Generally, yield is reduced by 20-30%, and in severe cases there is no harvest at all.
4. Soil. Rapeseed is a taproot crop with a relatively developed root system, a deep-reaching main root, and many lateral and fine roots. It requires deep soil layers, good structure, rich organic matter, and loam or sandy loam that both retains fertilizer and water and is loose and well aerated. In weakly acidic or neutral soil, it is more conducive to increasing yield and raising the oil content of the seeds.
Fertilization Methods for Rapeseed Planting
1. Apply sufficient base fertilizer. Generally, use 1000-1500 kg of compost and 20-25 kg of phosphate fertilizer per mu, mix evenly during land preparation and plow and harrow them into the topsoil. At the same time, use 1500-2000 kg of pig manure water, mixed with an appropriate amount of chemical nitrogen fertilizer, and apply it together into the seedbed soil to enrich the seedbed soil.
2. Apply thinning fertilizer appropriately. Before and after thinning, use about 500-750 kg of dilute human and livestock manure water per mu and sprinkle it 2-3 times. If the soil is dry and the seedlings are thin, more can be applied appropriately; if the soil is wet and the seedlings are strong, less can be applied. At the 4-5 leaf stage, focus on control, stop fertilizing and watering, and carry out seedling hardening to prevent excessive growth during the seedbed stage.
Control Methods for Rapeseed Aphids
1. Chemical control: 40% dimethoate emulsifiable concentrate or 40% omethoate 1000-2000 times solution, 50% dichlorvos emulsifiable concentrate 1000 times solution, 20% menazon 1000-1400 times solution, 50% malathion 1000-2000 times solution, 25% yamanqing emulsifiable concentrate 2000 times solution, 10% diazinon emulsifiable concentrate 1000 times solution, 50% pirimicarb wettable powder 3000 times solution, 50% monocrotophos emulsion 2000-3000 times solution, 40% phosfolan emulsion 1500 times solution, or 2.5% deltamethrin emulsion 3000 times solution
2. Seed treatment. Mix 1 kg of 20% menazon wettable powder with 100 kg of seed, or treat seeds with mephosfolan, phosfolan, or carbofuran to prevent aphids at the seedling stage.
3. Cultivation control. Cover about 50% of the ground with silver-gray, milky white, or black plastic film. It has the effect of repelling aphids and preventing viral disease.
4. Biological control. Rearing and releasing aphidius wasps, green lacewings, ladybugs, hoverflies, and entomophthoralean fungi can reduce aphid damage.
Rapeseed is generally planted in early autumn and can be eaten by winter. During the planting period, rapeseed needs relatively more water, so watering work must be done well. The management work in the later planting stage must be done properly, and timely fertilization and pest and disease control must be carried out in time, so as to ensure its yield.