EFFECT OF BORON FOLIAR APPLICATION AT CRITICAL GROWTH STAGES ON SUNFLOWER (HELIANTHUS ANNUUS L.) YIELD AND QUALITY

The objective of the reported vegetation experiment, established in 2008-2011, was to explore the effect of the date of foliar boron application on the yield and quality of sunflower. Four treatments were established in the experiment: 1) control - not fertilised with boron; 2) application of 300 g B ha(-1) in the growing stage of 4 developed leaves (V-4); 3) application of 300 g B ha(-1) at the beginning of elongation growth (R-1); and 4) split rate of boron application of 150 g B ha(-1) at stage V-4 (4 developed leaves) and 150 g B ha(-1) at stage R-1 (terminal bud forms). Foliar nutrition with boron increased the content of this element in leaves and stems, and raised the biomass production of sunflower plants. The increased uptake of nutrients by plants was essential for achene production. Application of boron fertilizer at stage V-4 increased the N content in the plant. Boron had a considerable effect on achene production. The highest increase in yields was related to the foliar boron application at stage V-4 (by 8.3% relatively). The relative increase in the oil content in response to boron application, which ranged within 1-2%, was not significant. The higher yields and a constant oil content increased oil production, most markedly after the boron foliar application at stage V-4 (by 10.2%). It was only the content of stearic acid that was increased significantly by foliar application of B at stage V-4 and split application (by 8.8% and 9.4%, respectively).