Effect of foliar products on the inflorescence yield of lavender and essential oil

The topic of the effect of foliar fertilization on the productivity and oil content of lavender is relevant, but not sufficiently studied. The present study aims to establish the effect of foliar products on the growth, development and productivity of lavender. The field experiment was carried out at the Agricultural University - Plovdiv with lavender of ‘Jubileina’ variety during 2019–2020. The following variants were included in the study: 1. Untreated control; 2. Treatment with Fertileader Gold (FG) - 3 L ha-1; 3. Treatment with Fertiactyl Trium + Fertileader Vital (FT + FVital) - 1.5 + 1.5 L ha-1; 4. Treatment with Fertileader Viti (FViti) - 3 L ha-1; 5. Treatment with Fertileader Vital (FV) - 3 L ha-1; 6. Treatment with Fertileader Alpha (FA) - 3 L ha-1. Those preparations are bio stimulants for foliar application. The treatments were made in two consecutive lavender vegetation seasons. The first application was carried out in the second growing season (2019) and the second in the next, third growing season (2020). The foliar application of all tested products increased the photosynthetic activity, but it was better expressed when using the plant nutrition products FV, FViti and FT + FVital. A positive effect was also observed in the height and diameter of the bush, but during the third vegetation period. The number of flowering stems increased by 62.9%; 59.4%; 53.3% and 8.4%, respectively, when applying the fertilizers FG, FT + FVital, FViti and FV. The application of FG and FT + FVital increased the yield of fresh inflorescences by 6.1% and 3.7%. The application of the different products affected the oil yield in different ways; the application of FG, FT + FVital and FViti increased it, while FV and FA decreased it by 27 kg ha-1 and 16 kg ha-1, respectively, for the first vegetation and by 43.4 kg ha-1and 33.1 kg ha-1 for the second vegetation. The boron containing products FG, FT + FVital and FViti led to a significant increase in the essential oil yield, while the application of the foliar fertilizers FV and FA reduced it. Based on those results, the first three products are recommended.