# Evaluation of the Effect of Biostimulation on the Yielding of Golden Delicious Apple Trees
## 3 Results and Discussion
In 8 of the 10 years of the study, the total yield of trees treated with biostimulant technology was higher than that in the control. Regardless of the combination used, the total yield during the entire study cycle was more than 60 t \(\times\) ha\({}^{-1}\) (Figure 1). The beneficial effect of preparations based on seaweed extracts on the yield quantity and quality was demonstrated by [39; 40; 41; 42; 43; 44]. The above-mentioned correlations were confirmed in the present study. During the research, a favorable effect of fertilization technology based on seaweed extracts on total yield was demonstrated compared to standard fertilization technology. Figure 1: Yield (kg-ha\({}^{-1}\)) evaluation of apple trees of Golden Delicious cultivar depending on fertilization technology (C—control; B—biostymulation). The technology based on biostimulant preparations had a favorable effect on the size of the marketable yield throughout the study cycle, but a different relationship was shown only in 2015 (Figure 2). Commercial yield in Control ranged from 4.2 to 93.7 t \(\times\) ha\({}^{-1}\) while in trees treated with biostimulants from 27.9 to 104.7 t \(\times\) ha\({}^{-1}\). The difference in commercial yield between the combinations used ranged from 2 to 42 tons. The largest yield differences were shown in 2009 (42.5 t); 2010 (30.4 t) and 2017 (23.7 t). It is worth noting that 2010 was the coldest and wettest year in the entire research cycle, similarly, in 2009, April recorded the lowest air temperatures of all the analyzed research years, while in 2017, the month of March was the coldest compared to the other research years, this had a direct impact on fruiting, It was shown that in 2009, 2010 and 2017, the biostimulant program, despite the inconvenient weather conditions, had a significantly favorable effect on the proportion of fruit above 7.5 cm and thus on the hand-lot yield. According to [PERSON] et al. [45], 2020 plant-derived biostimulants improve target plant growth and yield due to the presence of various phytohormones and other secondary metabolites, vitamins, antioxidants and inorganic nutrients in the extract, which can directly affect plant growth and production by improving plant tolerance against abiotic stresses (Figure 2). Figure 3 shows a cluster analysis of the percentage of fruit >7.5 cm of Golden Delicious apple trees for the entire study cycle depending on the fertilization technology (Figure 3a for the control combination. ; Figure 3b for the biostimulant technology). It was shown that in the case of the control, the years 2010 and 2017 strongly differed from the other clusters (study years), while in the case of the biostimulant technology, only 2017 differed from the other study years. It can be concluded that the application of seaweed-based preparations made it possible to achieve the percentage of large fruit in 2010 at the same level as in the rest of the study period and thus offset the impact of adverse weather conditions on the commercial yield. Similar observations were observed in 2017. According to [PERSON] et al. [46], 2011, the CBF3 (C-repeat-binding factor) gene from the brown macroalgae species A. nodosum is activated in response to low temperatures and dehydration and is independent of ABA. Similarly, the COR15A gene regulates cold tolerance by stabilizing chloroplast membranes [47]. The above relationships and influences can be confirmed in the present field observations. Figure 2: Influence of fertilization technology on the commercial yield (kg\(\cdot\)ha\({}^{-1}\)) of apple trees of the Golden Delicious variety (C—control; B—biostymulation). Table 4 shows the correlation analysis carried out between yield quantity and quality parameters and the type of production technology, i.e., control (lower part of the table) and biostimulation (upper part of the table). It was shown that regardless of the method of fertilization, fruit weight did not correlate with the number of apples per tree.