Abstract
<jats:p>The use of organic soil improvers in agriculture is directly related to limiting the application of mineral fertilizers and combating abiotic stress factors in a constantly changing climate. Viticulture is a significant industry that generates substantial profits worldwide, but it is not immune to the negative impacts of climate change. The search for solutions increasingly relies on studying the influence of natural products on plant growth and development. In the present study, the effect of the organic product Humat Rost on the photosynthesis, yields, and quality of the Merlot grapes in the village of Brestnik, Plovdiv region, was investigated. The product was applied either foliarly or in the soil at different doses and phenophases. The foliar treatment variants include V0 – control (without Humate Rost), V1 – 200 ml/ha, V2 – 300 ml/ha, V3 – dose 400 ml/ha, and V4 – 500 ml/ha Humate Rost, applied at the phenophases of appearance of the first tassel, before flowering, after mass flowering, grain growth and grain graying. The soil treatment has two variants, in which the product "Humate Rost" is applied as a solid residue, in two doses at the beginning of the vegetation: V5 – 15 kg/ha and V6 – 25 kg/ha. The indicators of leaf gas exchange and chlorophyll content were monitored dynamically. The yields and quality indicators of the grain, including sugars, acidity, etc., were recorded. Based on the results obtained, it can be concluded that Humate Rost enhances photosynthesis and increases chlorophyll content. A positive effect is also observed on the quality indicators of the grain. Keywords: climate change, Humat Rost, Merlot, photosynthesis, quality of grape</jats:p>