Macronutrient Status in Grapevine Leaves and Soil in Response to Fertilizers and Biostimulants

A field study was conducted on the plants of two grapevine cultivars, ‘Solaris’ and ‘Regent’, grafted onto an SO 4 rootstock (V. berlandieri × V. riparia) and characterized by strong growth and yield. The effect of twelve treatments on the concentration of macroelements in leaf blades in the véraison phase, as well as selected soil parameters, was assessed in the sixth, seventh and eighth year of their application. The following treatments were tested: control (no fertilization), NPK (mineral fertilization 70 kg N/ha; 40 kg P/ha; 120 kg K/ha), mycorrhizal substrate (AMF—arbuscular mycorrhizal fungi), NPK + AMF, manure before planting, NPK + manure before planting, BioIlsa, NPK + BioIlsa, BF-Ecomix, NPK + BF-Ecomix, Ausma, NPK + Ausma. The aim of the study was to assess the nutritional status of the two cultivars after long-term use of mineral fertilizers, organic fertilizers, biofertilizers and biostimulants under Polish conditions in soil with a low organic matter (SOM) content prone to acidification. AMF, organic fertilizers and biostimulants were not a sufficient alternative to mineral fertilizers, especially with regard to N supply. BF-Ecomix treatment increased the content of Mg in the soil and the soil pH value. Regular use of NPK fertilization increased the concentration of leaf N and K, but did not improve the nutritional status of plants with P, despite doubling its content in the soil compared to control. NPK fertilizers worsened the availability and accumulation of Mg and caused soil acidification, but resulted in a slight increase in total soil N and SOM. No significant differences were noted in the mineral status of both cultivars under the same fertilization treatments but liming improved the leaf Ca status in ‘Solaris’. Fertilization of grapevines, which have started to be cultivated in Poland due to the warming climate, requires further study. Mineral fertilization should not be routine, but rather constantly readjusted, taking into account the soil fertility and mineral status of plants, in order to use the nutrients more effectively and avoid their unfavorable effects on plants and soil.