Sunflower has several critical development stages, one of them is the 3–5 leaf pair stage. On different soil types plants may lack certain mineral nutrients. 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 more pronounced.
Symptoms of boron shortage
Symptoms of boron shortage show differently depending on weather conditions and hybrids. Upper leaves age quickly, dry up, turn dark and become brittle. Boron plays an important role from seed germination and later, in the course of growth, 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 at flowering. To supply sunflower plants at the 3–5 leaf pair stage we recommend using ECOLINE Boron (Premium) at 1.0 l/ha.
Using boron in combination with L-α amino acids
Using boron in combination with L-α amino acids promotes better and faster boron uptake and softens the negative effect of stress factors of various kinds. On soils with a low fertility level and a high spread of disease agents in the soil, to strengthen vegetative plant growth and hold back disease development it is advisable to feed with the tank mix ECOLINE Boron (Premium) at 1.0 l/ha + 1.0–1.5 l/ha of GROS Phosphito-NP. If deficiency of individual nutrients appears visually, or based on laboratory testing, other special fertilizers produced by ECOORGANIC can also be used for foliar feeding of sunflower plants.