Mineral Nutrition of Sunflower

Sunflower, the main oilseed crop in Ukraine, occupies large sowing areas in the Steppe and Forest-Steppe and in recent years is grown even in Polissia. The crop is demanding in mineral nutrition, so maximum supply of mineral fertilizer needs from autumn is desirable.

On fields where the full dose of mineral fertilizers was not applied in autumn, the effectiveness of their localized spring application grows. For at-sowing application ECOORGANIC offers the novelty of the 2019 season, the liquid starter fertilizer Fitostart Jet. It contains amide nitrogen at 100 g/l and phosphorus at 300 g/l in the form of phosphate and phosphite.

To form yield, sunflower needs a large amount of nutrients, especially when growing 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 requires a lot of nitrogen and phosphorus, and in potassium removal it has no equal at all. To form 20 c/ha of seed, sunflower removes: nitrogen 80–100 kg/ha, phosphorus 30–50 kg/ha, potassium 150–250 kg/ha. All by-products, containing on average 50 kg/ha of nitrogen, 25 kg/ha of phosphorus and 180–200 kg/ha of potassium, stay in the field.

During the growing season sunflower takes up nutrients unevenly: a significant amount of nitrogen and phosphorus before flowering, when leaves, stem and roots form, and potassium almost throughout the growing season, but especially intensively before flowering.

Mineral nutrients affect plants differently. For example, nitrogen strengthens 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 (because protein content in seed rises while oil content falls sharply). In such conditions the likelihood of plant lodging and infection with diseases (phomopsis, white rot) increases.

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 withstand hot dry winds and soil moisture shortage better. Increased phosphorus nutrition sharply reduces the water consumption coefficient of sunflower plants.

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 powerful root, which under favorable conditions can reach 3 m deep, which 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, since the layer where the fertilizers sit dries out quickly and phosphorus becomes unavailable, so in this period liquid starter fertilizers with a high phosphorus content are preferable.

Potassium deficiency also adversely affects sunflower plants: stems become brittle and thin, the oil content of seed falls, sunflower yield drops, and the content of saturated and unsaturated fatty acids 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 these problems.

To supply plants with phosphorus with a high uptake coefficient, ECOORGANIC offers the special fertilizer Ecoline Phosphite (K). The phosphorus in this product is in phosphite form, whose uptake within 24 hours is about 60–70% of the applied amount. Besides 530 g/l of phosphorus as phosphite, the product contains potassium at 350 g/l and boron at 14 g/l (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 has a fungicidal action on fungal pathogens. If acute potassium deficiency appears, foliar feeding can be done with the fertilizer Fitostart Potassium with a potassium content of 300 g/l at 3–4 l/ha.

Microelements, which regulate physiological processes in the plant, are of great importance in the mineral nutrition of this crop. Telling were the results of assessing photosynthetic productivity of sunflower plants after applying microelement-enriched superphosphates under pre-sowing cultivation (Tab. 1). With foliar feeding with microelements this tendency persists.

Tab. 1. Photosynthetic productivity, g/(cm2·day) (Anspok P.I. 1990)

Several development stages of sunflower are singled out as 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 biologically active substances should be added. A reserve of microelements and biologically active substances on the seed surface raises germination energy, relieves stress from external environmental factors and crop protection products, stimulates development of the root system and of the plant as a whole, and raises disease resistance.

For pre-sowing seed treatment ECOORGANIC suggests using the special fertilizer Gros Rootgrowth at 1.5–1.8 l/t of seed, separately or combined with Ecoline Phosphite (K) at 1.3–1.5 l/t of seed.

Effectiveness of pre-sowing treatment with the fertilizer Gros Rootgrowth

Demo plot of ECOORGANIC LLC, Kyiv region, 2016. Assessment 4 weeks after sowing

Particular attention should be paid to feeding sunflower with boron. A soil boron content of 5.0 mg/kg of soil is the limit below which the first symptoms of boron shortage begin to appear. These symptoms show differently on different parts of the 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 level of boron shortage: with severe shortage, for example, the head falls off completely, as with insect damage.

Boron plays an important role from the moment of seed germination and further throughout ontogeny in regulating carbohydrate metabolism, the synthesis of amino acids, proteins and chlorophyll, and pollination at flowering. This element 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 and is non-toxic to plants.

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 special fertilizer Ecoline Boron (Premium) at 1.0–2.0 l/ha. Besides 140 g/l of boroethanolamine, this product 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 factor limiting 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, as a result of which growth of aboveground mass predominates over the root, plants stretch and become brittle and susceptible to disease. To overcome such problems we recommend the microfertilizer Ecoline Manganese (Chelate), which 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, thereby limiting the future yield. In addition, plants not sufficiently supplied with boron, manganese and zinc cannot form seed of higher mass, so it is important to feed them again before flowering. Effective in this period is foliar feeding with the microfertilizer Ecoline Oilseed (Chelates) at 1.0–2.0 l/ha.

Practical experience shows that the system of foliar feedings on sunflower is highly effective. With this agronomic measure, seed yield can be increased and its oil content raised 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 Ecoline Phosphite (K-Amino), which besides 250 g/l of phosphorus as phosphite and 170 g/l of potassium contains 70 g/l of L-α-amino acids. This combination of nutrients and amino acids not only provides additional phosphorus and potassium feeding but also helps the plant come out of the stress situation with minimal losses. Also, to overcome stress situations and supply sunflower with a microelement complex, we recommend the microfertilizer Ecoline Universal Growth (Amino) at 1.0–2.0 l/ha. This foliar fertilizer contains a balanced composition of microelements needed for full plant nutrition (Mg, Fe, Mn, Zn, Cu – 100% EDTA chelates) and 75 g/l of L-α-amino acids.

Thus, with the help of ECOORGANIC LLC fertilizers the problem of nutrient shortage can be solved at all stages of sunflower development: Gros Rootgrowth, Ecoline Phosphite (K) - for pre-sowing seed treatment, Fitostart Jet or Fitostart Potassium – application at sowing, Ecoline Universal Growth (Amino), Ecoline Phosphite (K-Amino), Ecoline Boron (Premium) - for application at stages from 2 to 8 leaf pairs to reduce the aftereffect of crop protection products, Ecoline Boron (Organic), Gros Quicelium, Ecoline Oilseed (Chelates) – to supply the necessary nutrients during the period from head formation to ripening.