Principles of application
Sunflower is the main oil crop in Ukraine with high profitability. To get 1 t of grainwith the corresponding amount of byproducts, sunflower consumes 45-55 kg of N, 15-25 kg of P2O5, 100-120 kg of K2O. About 26 kg of N, 12 kg of P2O5 and 10 kg of K2O are to be applied directly with the seeds. The rest of nutrients at about 70-75% of N, 50-55% of phosphorous and up to 93% of potassium which are needed to form yieldincluding non-market production return to the soil for the next crop rotation. It is inappropriate to speak about soil depletion by sunflowers, because sunflowers have well-developed root system and in the process of their development are able to adsorb nutrients from deep soil and move them to topsoil with byproducts from which nutrients are released under biological and chemical factors. Intensively moisture absorption by sunflower runs soil dry. Transpiration coefficientis one of the highest among crops.Sunflower fertilization program is based on basal, at sowing application and feeding. Basal and at sowing application are the most effective.N10-15 or N10-15P15-30 should be used during at sowing application. Complete at sowing application requires N10-15P10-15K10-15. Feeding is efficient in case of insufficient basal fertilization,adverse weather condition or visiblesigns ofstarvation in the early growth stage. Feeding is practically non-effective in the later stages.
At the stage of the growth and before the beginning of the basket formation sunflowers moderately consume nitrogen and potassium and intensively consume phosphorous. From the beginning of the basket formationand before the beginning of flowering, nitrogen, phosphorous and potassium are taken upwith maximum intensity.In flowering and until the seeds are ripe, sunflowers moderately consume nitrogen and phosphorous and intensively consume potassium.
Excessive nitrogen nutrition at the initial growth stages decreases yield, that is why it is better to use amid and ammonia forms of nitrogen fertilizers with prolonged effect. Nitrate formsfacilitaterapid vegetative mass growth, but push back the formation of basket that in the end leads to yield decreasing.Up to 80%of nitrogen is consumed by the end of the flowering.
Sufficient phosphorous nutrition is important at the beginning of growth for root system development, during the seeds formation and oil accumulation.
Potassium is adsorbed by sunflower throughout the vegetation, maximum intensity is observed from the beginning of basket formation and until the end of flowering. At the time of seeds developmentinsufficient potassium nutrition decreases yield, oil contentin seeds, unbalances the level ofsaturated and unsaturated fatty acids. In case of poor content of exchangeable potassium in the soil, potassium fertilizerdefines the yield.
Sulphur nutrition influences oil content.