Growth, Yielding and Healthiness of Grapevine Cultivars ‘Solaris’ and ‘Regent’ in Response to Fertilizers and Biostimulants

In the years 2008–2015, field experiments were conducted on the vines of cultivars ‘Solaris’ and ‘Regent’ grafted on SO4 rootstock. The following treatments: 1. control (untreated), 2. NPK (mineral fertilization 70 kg N·ha⁻¹; 40 kg P·ha⁻¹; 120 kg K·ha⁻¹), 3. mycorrhizal substrate (AMF – Arbuscular Mycorrhizal Fungi), 4. NPK + AMF, 5. manure (before planting), 6. NPK + manure (before planting), 7. Bioilsa, 8. NPK + Bioilsa, 9. BF-Ecomix, 10. NPK + BF-Ecomix, 11. Ausma and 12. NPK + Ausma were applied to evaluate the usefulness of biostimulants and mineral and organic fertilizers in organic grapevine production in “cool climate” conditions of Poland. The tests did not show a definite positive effect of the biostimulants and organic fertilizers on growth, yielding and healthiness of the cultivars ‘Solaris’ and ‘Regent’. There were no substantial differences in total marketable yield in the years 2009 to 2015 between control and other treatments. Grapevines planted in soil rich in minerals grew and yielded well despite no mineral fertilization for a number of years. In 2014, when the air humidity was high during vegetation, intensive rotting of the berries of cultivar ‘Solaris’, caused by Botrytis cinerea, was observed on plants fertilized with NPK.