Sunflower has a strong root system, with penetrating debth into the soil for about of 4 m. The horizontal coverage of a single plant is 1-1.2 m. Sunflowers has a big requirements to potassium level, but thanks to a powerful root system they can independently extract the quantities of this trace element they need in the soil and therefore the agrarian can not always see the positive effect of potassium application on the crop.
For the formation of 1 ton of grain sunflower takes from the soil:
It is believed that the sunflower greatly depletes the soil. However, its plant residues can significantly improve the situation after harvest. The table below allows you to compare the effect of different crops on the removal of nutrients from the soil.
The process of assimilation of nutrients takes place unevenly in time. The beginning of growth is characterized by low consumption of nutrients. Their absorption exceeds the growth rate of dry mass. The initial stage (2-3 pairs of sheets) is important because at this time the basket is formed. Absorbed 10% of nitrogen, phosphorus and potassium of total need.
Over the next 1.5 months, during which the baskets are formed, right up to the end of the flowering phase, sunflower consumes 80% of all nitrogen, 70% of total phosphorus and 50% of potassium.
The remaining part of potassium - 40%, will be absorbed from the seed creating stage before the start of ripening. A powerful root system allows the sunflower to extract potassium even from deep layers, but if the soil is poor throughout the depth, then you should think about feeding with potassium. On poor soils, the introduction of one kilogram of potassium can give a gain of 2-3 kg of seeds.
Assimilated after the seed pouring phase, nitrogen promotes the formation of tissues that store oil. The increased level of nutrition with phosphorus at this time contributes to the accumulation of oil in the seeds.
Nitrogen entering plants in the seed loading phase accelerates the formation of proteins instead of fats. Phosphorus at this time contributes to a more intensive synthesis of nucleic acids and phospholipids, increases the content of linoleic acid and water-soluble proteins in oil.
As already written above, sunflower is a potassium culture and its root system very actively extracts potassium from the soil. But if there is not enough potassium in the soil, the harvest directly depends on the timely introduction of potash fertilizers.
Signs of lack of potassium: leaves shriveled, dome-shaped, lower leaves turn yellow first, then turn brown, the stem of the plant is thin, weak, bends in the upper part.
Conventionally, in the life of sunflower there are three stages in the assimilation speed of the nutrients.
Nitrogen enhances plant growth, contributes to the formation of larger baskets. But an excess of nitrogen causes an excessive formation of the vegetative mass, the irrational use of fluid, which leads to its lack during critical periods (flowering and seed forming). Sensitivity to causative agents of diseases, wilting increases. In the seeds, an increase in the amount of protein is observed with a decrease in the oil content (normally it should be the other way round).
The best option would be moderate nitrogen nutrition before the appearance of baskets and increased between the phases of budding and flowering.
With a lack of nitrogen, there is a decrease in the number of seeds in the basket.
Phosphorus contributes to the development of the root system (as with other cereals), is responsible for laying the reproductive organs, the number of flowers in the basket. With the optimal amount of phosphorus, the growth and development of the plant is accelerated, moisture is used more rationally, and more oil accumulates in the seeds.
In general, nitrogen and phosphate fertilizers complement each other in terms of their influence on the growth, development and ripening of seeds.
Sunflower is a very active consumer of potassium - in order to create 1 ton of seeds it takes 100-150 kg/ha of this mineral. A sufficient amount of it has a positive effect on photosynthesis and carbohydrate metabolism. Usually, thanks to a powerful root system, the sunflower independently extracts all the necessary potassium from the soil. Therefore, to make this mineral is necessary only if its content in the soil is reduced.Sulfur
A sufficient amount of sulfur improves nitrogen metabolism, increases the yield and the amount of oil in the seeds. With a lack of sulfur, the leaves become a pale green (yellow) color, spotted chlorosis is noted, the growth of the plant as a whole slows down. You can expect a lack of sulfur on the ground:
The fertilizer system for sunflower is divided into three methods: basic, row and fertilizer. Sunflower responds well to aftereffects of organic fertilizers, therefore it is well suited as a follower crop for wheat and others under which manure was applied.
When applying to the field of 20-30 t/ha of manure, we can expect an increase in yield of 0.2-0.5 t/ha. Fertilization using the technology No-Till gives good results in the first years of use. From 1 kg of fertilizer can be expected 1.2-1.5 kg of sunflower seed.
Manure, phosphate and potash fertilizers are recommended to be applied under the autumn tillage. Nitrogen - under pre-sowing cultivation. As an option, it is possible to add full fertilizer in the spring to a depth of 12-14 cm. Or, apply a superphosphate (or complex fertilizers) by the row-method during sowing.
If there is enough moisture, then in the fields without basic application it is possible to dispense with the feeding of phosphorus and potassium in the phase of 2-3 pairs of leaves.
Foliar feeding is rarely used - to make nitrogen, phosphorus or trace elements. In the case of slower growth of plants in the cold using nitrogen fertilizers. At the beginning of the growing season, phosphorus is used to accelerate the development of the root system.
When growing sunflower on the same field for more than 2 years in a row, it is necessary to make mineral fertilizers. It is important that their distribution on the field was uniform, without strips of overdose and lack.
The phase of 2-3 pairs of leaflets and the phase of budding (8-10 leaves) have a critical value on the content of microelements. The lack of boron, zinc, manganese and molybdenum at these stages significantly reduces the yield.
For the formation of 1 ton of grain, sunflower takes from the soil: iron - 210 g., Copper - 17 g., Zinc - 100 g., Manganese - 118 g., Boron - 113 g.
|Taken from the soil (grams)
|How much % will go with the seeds
First you need to consider boron - sunflower is very sensitive to the lack of this element. Boron is responsible for the development of pollen, pollination, increases the number of seeds in the basket, increases the overall yield of the crop.
With a lack of boron, the leaves are severely deformed due to the death of the tissues near their base, the plants are lagging behind in growth rate, the heads of flowers are deformed. With a strong boron deficiency, some inflorescences do not appear at all and the growing points die. Most often, the disadvantage of this element can be expected:
The critical value of the content in the soil is 0.5-3 mg/kg. The usual dose of 1-2 kg/ha (active ingredient). It is better if boron is delivered to the plant by the foliar method, dividing the full dose into several applications. Getting into the soil, boron gradually turns into inaccessible compounds for plants. It is better to carry out foliar top dressings in such phases of growth:
Possible pre-treatment of seeds.
Manganese is needed for the normal uptake of nitrogen by the plant, phosphorus, also, it is important for protein metabolism. With its deficiency, the leaves turn yellow first on the tops and along the edges, then the yellowness passes between the veins and the leaf fades. First, the old leaves are damaged. A lack of manganese should be expected on acidic and sandy soils, with a high content of potassium and at low temperatures. The recommended dose of 50-80 kg/ha in the soil or sheet feeding, where the dose is slightly lower.
Manganese is responsible for the following processes:
Its lack manifests with a chlorotic spots on young leaves. At the same time old and very young leaves are not affected. It is best to add manganese together with molybdenum and other trace elements using the foliar method - on the leaves in the form of chelates along with herbicide treatment.
The best periods for foliar feeding with micronutrients of phases 3-4 and 5-6 pairs of leaves, when the plant grows actively and baskets are laid.