The duration of the growing season for winter rape is 90-120 days: 60-80 in the fall and 90-110 days in the spring, after getting out of winter sleep. To increase yield, rapeseeds need sufficient doses of nutrients and a pH in the range of 6.2 - 7.0. At a pH of more than 6.5, the damage to rapeseed by cabbage tip is reduced, but the plants grow worse due to the lack of trace elements. Rapeseed forms a strong root system, but does not respond well to an overly compacted soil.
| To grow one ton of seeds would takes from the soil | % return to the soil with crop residues | |
| Nitrogen | 56-60 kg | 60% |
| Phosphorus | 20-25 kg | 36% |
| Potassium | 40-50 kg | 71% |
That is, rapeseed takes more nutrients from the soil than cereals, especially phosphorus. It responds well to the aftereffect of organic fertilizers that have been applied under the predecessor. A full dose of phosphate and potash fertilizers for rapeseed should be applied after harvesting the predecessor for the main treatment.
Three critical periods of rapeseed growth
Canola reacts best to nitrogen fertilizers. Usually, nitrogen is introduced during pre-sowing cultivation at a dose of 100-120 kg/ha. On soils of light particle size distribution and with enough moisture for a more rational use of fertilizers, the dose is divided into two methods of application: before the start of sowing 50-60 kg/ha and the rest in the form of top dressing in the phase of 4-6 leaves.
The autumn period for winter rape is an important step in preparing for wintering. During the autumn growth period, 25% of the total nitrogen is absorbed. Another 35% will be absorbed during the vegetation recovery period, 30% at the beginning of the flowering phase and the remaining 10% at the end of flowering. The nitrogen consumption from the soil in the fall is 60-80 kg/ha. For optimal development of rapeseed, the dose of autumn fertilizer is determined as the difference between the need of a plant and residues in the soil.
If the average value of nitrogen residues in the soil is 30-40 kg/ha, in the autumn it is necessary to apply at least 40 kg/ha of nitrogen fertilizers so the rapeseed to could prepare for wintering. Signs of readiness for winter rapeseed:
There is an approximate formula for calculating the expected yield from the results of plant inspection in the fall (before wintering begins):
Expected yield (c / ha) = 0.1 * (number of leaves per plant +1) * number of plants per 1 m².
It is not recommended to feed rapeseed later the 4-5 leaf phase in the fall, as in this case the water content in plant tissues increases and resistance to low temperatures decreases. If there was no presowing application of nitrogen fertilizers and signs of nitrogen deficiency appeared, you should add 20-30 kg/ha of these fertilizers by October. You can suspect a lack of nitrogen by the following signs: after germination, the leaves are light green in color, the growth rate is lower than usual, some leaves turn red or turn yellow. In this case it is necessary to make the top dressing, as variant - as a foliar application of 8-10% urea solution.
It is believed that the upcoming harvest by 70% depends on the nutrition and development of plants in the autumn period until the moment of hibernation. The plant goes into wintering mode after 5 days in a row the temperature does not exceed 2°.
This culture is more demanding on the presence of phosphorus in the soil than grain crops. Intensely, it absorbs phosphorus in the period between stem formation and flowering (2-3 kg/ha per day). This mineral is important for:
Rape can mobilize soil phosphorus from poorly soluble compounds, under it you can use all forms of phosphate fertilizers. The recommended dose of 60-90 kg/ha.
In the fall, rapeseed absorbs up to 30% of the total potassium it will need for growth. Moreover, most of it goes precisely for the formation of a stock, and not for the formation of dry mass. This element is important for the synthesis of a sufficient amount of carbohydrates, which increase the resistance of plants to cold and therefore are necessary for wintering. A higher content of carbohydrates in the tissues of the plant enhances the absorption capacity of the root system.
The effect of potassium on rapeseed growth:
Since magnesium is an essential component of chlorophyll and a number of enzymes, its deficiency reduces the yield. In autumn, this metal is very important for the transportation of sugars from the leaves to the roots, without which the formation of the root system is impossible. With a sufficient amount of magnesium, the oil content in grains increases.
A sign of a lack of magnesium is the marbling of the leaves (venous chlorosis). Old leaves turn yellow between the veins, in some varieties - red. Brown or purple spots appear at the edges of the leaves. More often expect magnesium deficiency on sandy and acidic soils.
The rapeseed plants damaged by hibernation are quickly restored after feeding with a 5% solution of magnesium sulfate. Even at low temperatures, it quickly penetrates the plant's cells, does not damage tissue, improves the absorption of sulfur.
The canolas need in sulfur is higher than that of cereals and amounts to 10-15 kg/ha. With a lack of sulfur:
The highest demand for sulfur is noted in rapeseed from the beginning of stem formation to the setting of the pods. Signs of sulfur deficiency are similar to those of nitrogen deficiency. In plants, chlorosis begins (the color of the leaves may become light green, light yellow, red), the veins begins to stain, the leaves becomes deformed, taking the form of a spoon. Further, there is a delay in the growth of the plant as a whole and the deformation of the pods. Productivity is also reduced. Most often this can be expected on soils light grain size distribution or low humus content.
Depending on the current amount in the soil, sulfuric fertilizers can be applied under the main treatment in a dose of 30-80 kg/ha. It should be borne in mind that an excess of sulfur can lead to an increased content of glucosinates in the seeds. Therefore, it is recommended to use a dose of sulfur, which is 25% of the applied nitrogen. If organic fertilizers are used, then 20 kg/ha of sulfur will suffice. For rapeseed and cabbage crops, ammonium sulfate can be used as a source of sulfur.
The foliar way of sulfur top-dressing is used only for acute deficiency and before flowering.
With a yield of 3 t/ha, rape takes from the soil:
In areas where soil liming was carried out, molybdenum is not used.
It is very important to provide a sufficient amount of boron at the stages of active growth of the stem and shoots, as well as, at the beginning of flowering, in order to reduce the fall of the flowers. Feeding boron can be carried out simultaneously with the use of insecticides. The recommended dose of application is 200-400 g/ha. It is not recommended to applicate more than 3 kg/ha, as this may reduce the growth of the next plant culture on this field.
If there is boron deficite after the formation of the outlet, could be delay in flowering, the leaves would be twisted and wrinkled along the edges. On the old leaves appears spots of red and red-purple. If there are flowers, the plant is as if struck by a color beetle. The pods will be formed unevenly, the seeds quantity is smaller than usual, the weight of each seed is reduced.
The foliar method of boron top-dressing is used if the symptoms of acute insufficiency detected, usually in the rosette growth, budding and autumn phases, before going to winter rest. Good results are obtained by foliar feeding with boric acid in the phase of green pods.
Manganese is needed for rapeseed to carry out the process of nitrate reduction, as well as in photosynthesis and protein synthesis. Signs of deficiency:
You can expect a shortage of manganese:
Good results are obtained by foliar application of manganese in the phase of a large burgeon.
Growing canola, the farmer can expect a shortage of molybdenum on acidic soils (pH less than 5.5), especially after the introduction of high doses of nitrate fertilizers. Symptoms of molybdenum deficiency are necrotic spots on the leaves and further along the edges of the leaf plates. Further leaves wither, become spoon-shaped. Flowers quantity in this case is less.
For the prevention of deficiency, seeds are treated with ammonium molybdate, with an acute shortage of this element during growth, foliar feeding is carried out with a 0.1% solution (100 g/ha).
You can expect a lack of copper on the soils of light particle size distribution after liming.
Zinc deficiency can occur during drought and on neutral soils. Zinc is better to use in the form of chelates along with pesticides.
