Foliar Feeding of Sunflower

Sunflower is a crop of intensive mineral nutrition, demanding in soil nutrient reserves, so applying the full dose of mineral fertilizers from autumn is a necessary requirement. On fields where the full dose of mineral fertilizers is not applied in autumn, the effectiveness of their localized spring application grows. The total amount of nutrients that sunflower uses to form yield reaches considerable values, especially when sown with intensive hybrids whose yield reaches 35–45 c/ha. Nutrient removal is determined by the hybrid's productivity and by specific soil and climate, agronomic and organizational conditions. Compared with other field crops, sunflower removes large amounts of nitrogen and phosphorus, and in potassium removal it has no equal at all. To form 20 c/ha of seed, the following are removed: nitrogen 56–58 kg/ha, phosphorus 22 kg/ha, potassium 30 kg/ha. All by-products, containing 50 kg/ha of nitrogen, 25 kg/ha of phosphorus and 180–200 kg/ha of potassium, remain in the field. During the growing season sunflower takes up nutrients unevenly. A large amount of nitrogen and phosphorus is taken up before flowering, when leaves, stem and roots form. After heads appear, phosphorus uptake falls sharply. Potassium is taken up by sunflower plants almost throughout the whole growing season, but especially intensively before flowering. For sunflower there are several development stages critical for yield: seed germination, head laying down and the start of flowering. During germination plants are sensitive to temperature swings, moisture shortage, soil herbicides and diseases, so besides treating seed with fungicides and insecticides, microelements and stimulators should be added. A reserve of microelements and stimulators on the seed surface raises germination energy, relieves stress from external environmental factors and crop protection products, stimulates root system development, and increases disease resistance. Ecoorganic offers to use for this purpose the special fertilizer Ecoline Universal Seed at 1.5–1.8 l/t of seed with the addition of Ecoline Phosphite K at 1.3–1.5 l/t of seed. Nutrients act differently. For example, nitrogen strengthens plant growth and promotes the formation of larger plants and heads. However, excess nitrogen nutrition lengthens the growing season and adversely affects oil accumulation in seed (protein content in seed rises while oil content falls sharply). With excess nitrogen nutrition the likelihood of plant lodging and infection with diseases (phomopsis, white rot) increases.

Photo 1. Signs of nitrogen shortage in sunflower

Phosphorus promotes more powerful root system development and the laying down of reproductive organs with a large number of embryonic flowers in the head, so it is important in the early stages of development, up to 3–4 pairs of true leaves. With sufficient phosphorus nutrition plant development speeds up and moisture is used more rationally, so plants endure hot dry winds and soil moisture shortage more steadily. With increased phosphorus nutrition the water consumption coefficient of sunflower plants falls sharply.
It must be remembered that when growing sunflower on soils with an alkaline soil solution reaction, uptake of the important nutrient phosphorus worsens. There is still a practice of fertilizing sunflower crops only with nitrogen and applying no phosphorus and potassium. Phosphorus is needed not only to ensure energy and growth processes in the plant but also as an element for growing a strong root. It is known that sunflower is a drought-resistant crop. But this requires a powerful root, which under favorable conditions can reach 3 m deep. A powerful root system improves uptake not only of moisture but also of nutrients from the deeper soil layer. In the dry zone, applying phosphorus under cultivation is not very effective, because the layer where the fertilizers sit dries out quickly (phosphorus becomes unavailable). It is better to apply phosphorus and potassium in autumn under basic tillage, when the fertilizers get to depths where they can work. When potassium deficiency arises, sunflower plant stems become brittle and thin. Insufficient potassium nutrition leads to the formation of seed with little oil content, sunflower yield falls, and the content of saturated and unsaturated fatty acids also changes. On soils poor in potassium, plant growth is difficult. Young leaves develop in dense rosettes and eventually turn into brown dead «patches». Applying appropriate amounts of potassium fertilizers can prevent this problem.

Photo 2. Signs of phosphorus shortage

In practice, situations quite often arise when, for lack of funds or other reasons, phosphorus and potassium were not applied under basic tillage, cultivation or in the row at sowing. In this case applying these nutrients by foliar application becomes a technological necessity, but other problems arise here. Phosphorus in the most usual, phosphate form is absorbed through the leaf surface very slowly and in small amounts (about 20% of the applied amount within 5 days).
The solution to these problems is using the special fertilizer Ecoline Phosphite K from Ecoorganic at 1.0–2.0 l/ha. The phosphorus in this product is in phosphite form, whose uptake rate is about 60–70% of the applied amount within 24 hours. Besides 530 g/l of phosphorus in the form of phosphite, the product contains 350 g/l of potassium and 14 g/l of boron. This is the highest concentration among all products of this class on the market. Besides additional phosphorus and potassium nutrition, the foliar nutrition fertilizer Ecoline Phosphite K promotes active root system growth and shows a fungicidal action on fungal disease agents. On different soil types a shortage of microelements may be felt. Particular attention should be paid to feeding sunflower with boron.A soil boron content of 5.0 mg/1 kg of soil is the limit beyond which the first symptoms of boron shortage begin to appear, and at a content below 3.0 mg these symptoms can be very strong.

Photo 3. Signs of potassium shortage

Symptoms of boron shortage show differently on different parts of plants (on leaves, on the head) depending on weather conditions and hybrids. Upper leaves age quickly, dry up, turn dark and become brittle. On the head these symptoms can also show differently depending on the degree of boron shortage: with severe shortage, for example, the head falls off completely, as with insect damage.
Boron plays an important role from seed germination and further in regulating carbohydrate metabolism, the synthesis of amino acids, proteins and chlorophyll, and fertilization processes at flowering. Boron is also important for sunflower root system development. It improves the outflow of carbohydrates to the root system and activates its growth. Because of the absence of reutilization (the possibility of moving from old tissues to new), sunflower's need for boron remains high throughout the whole growing season, especially rising at flowering. To supply boron, it is better to use fertilizers in which it is in organic form, boroethanolamine. In this form it is taken up much faster, is non-toxic to plants and is taken up by plants including through the root when it gets into the soil.

Photo 4. Signs of boron shortage

For feeding sunflower plants with boron we recommend using one of the most concentrated and high-quality products on the market, the microfertilizer Ecoline Boron Organic at 1.0–2.0 l/ha. A better effect is achieved with two applications at half doses. If plants are under stress when boron fertilizers are applied, Ecoorganic recommends applying the innovative microfertilizer Ecoline Boron Premium at 1.0–2.0 l/ha. Besides 140 g/l of boroethanolamine, the microfertilizer contains 10 g/l of L-α-amino acids, which help the plant come out of the stress situation quickly. On limed, alkaline and sandy soils uptake of phosphorus, boron, manganese, iron and zinc is disrupted, which is a limiting factor in sunflower nutrition. Uptake of manganese worsens especially on alkaline and sandy soils. Manganese plays an important role in the nitrogen uptake cycle. With its shortage the nitrate nitrogen content in the plant rises, while growth of aboveground mass predominates over the root, plants stretch and become brittle and susceptible to disease. To overcome these problems we recommend the microfertilizer Ecoline Manganese Chelate at 1.0–1.5 l/ha. This product contains 60 g/l of manganese in the form of 100% EDTA chelate. A very important stage for correcting sunflower mineral nutrition is the formation of 5–8 pairs of true leaves. In this period the future head is laid down. With unbalanced nutrition or stress, the head is laid down with fewer flowers, limiting the possibilities of the future yield. In addition, plants not sufficiently supplied with boron, manganese and zinc cannot form seed of greater mass. For this it is important to repeat feeding before the start of flowering. Effective in this period is foliar feeding of plants with the microfertilizer Ecoline Oilseed Chelates at 1.0–2.0 l/ha. This microfertilizer contains a composition of microelements balanced from the point of view of sunflower plants. It should be noted that Mg, Fe, Mn, Zn, Cu in the microfertilizer Ecoline Oilseed Chelates, are 100% chelated with EDTA. Practical experience shows that the system of foliar feedings on sunflower is highly effective. With this agronomic measure seed yield can be raised by 1.3–3.0 c/ha and its oil content by 0.2–0.5%.
Stress situations caused by adverse weather or the action of crop protection products have a very great influence on sunflower yield formation. In the early stages of development the phytotoxic effect of soil herbicides leached close to the seed level is often observed, often intensified by low temperatures. In this period we recommend using the unique special fertilizer Ecoline Phosphite K-Amino at 1.0–2.0 l/ha. Besides 250 g/l of phosphorus in phosphite form and 170 g/l of potassium, the product contains 70 g/l of L-α-amino acids. This combination of nutrients not only gives additional phosphorus and potassium feeding but also helps the plant come out of the stress situation with minimal losses.
Stress situations also appear in later periods of sunflower development, 3–8 pairs of true leaves. At this time stress situations are possible from graminicide herbicides or from weather conditions (drought, hail, etc.). At this time Ecoorganic recommends using the microfertilizer Ecoline Universal Growth Amino at 1.0–2.0 l/ha to overcome stress situations. This foliar nutrition fertilizer contains a balanced composition of macro- and microelements needed to support plant nutrition, in which Mg, Fe, Mn, Zn, Cu are 100% chelated with EDTA. In addition, the microfertilizer includes 75 g/l of L-α-amino acids needed to overcome stress situations and for active plant growth. Recently more and more sunflower hybrids resistant to Eurolightning are being sown. When using the Clearfield system, sunflower can often be suppressed, showing as yellowing of leaves. Stress from Eurolightning can reduce growth rates and yield potential, since plants can remain in this state for 10–12 days. Using anti-stress microfertilizers containing amino acids and quickly absorbed forms of phosphorus and potassium can shorten the stress period to 3–4 days. Experience has shown that anti-stress products must be added to tank mixes with Eurolightning. Ecoorganic offers to bring plants out of stress using Ecoline Phosphite K-Amino at 1.5–2.5 l/ha, or Ecoline Universal Growth Amino at the same dose. The same sunflower foliar feeding scheme is quite suitable on crops of hybrids resistant to tribenuron-methyl (so-called «Granstar-tolerant» hybrids). In this case it is better to carry out feeding not at the same time as applying the herbicide Granstar (or its analogues), but 1–3 days after its use. When using microfertilizers in the same tank mix with a herbicide a compatibility test MUST be done!