## 4 Discussion  
Research indicates that digestate holds significant potential for use in vegetable cultivation. Digestate can produce tomato yields comparable to, or even exceeding, those achieved with mineral fertilizers [21,22,37]. However, our research showed that digestate did not significantly affect tomato yield (Table 5). Furthermore, a higher amount of digestate increases nonmarketable yield, which goes to waste (Table 5). While yield is certainly an important factor, it is not the only consideration regarding the use of digestate. In this study, we did not focus on yield; instead, we examined how different proportions of digestate mixed with peat influence the antioxidant system in tomatoes. In this experiment, a digestate additive was incorporated into the substrate to promote seedling growth. Following transplantation into the greenhouse, uniform fertilization and care were provided for all variants. This sequential treatment helps to highlight the relationship between seedling quality and harvest quality under the same growing conditions after transplanting. Our findings reveal that antioxidant activity is affected by the ratio of digestate in the peat mixture (Tables 1-4). Also, our findings correlate with results from a study conducted by [PERSON] et al. [25] where antioxidant activity was increased by using digestate as fertilizer, and it also suggests the activity rise to be present because of vitamin C content changes. [PERSON] et al. [29] stated the same antioxidant activity and ascorbic acid increase when digestate was used as tomato fertilizer. In the studies referenced above, digestate was used as a substitute for conventional fertilizers. The use of digestate for the cultivation of leafy vegetables was not very successful, but in the case of salinity stress, the results obtained when growing with digestates showed a decrease in stress and an increase in yield [37]. Thus, the benefits of digestate also depend on the composition of the main substrate. The results of our study show that the increasing ratio of digestate in the peat substrate had different effects on different indicators of antioxidant stress (Table 5) [25,39]. However, the exact effect on the phenolic content of plants may vary depending on several factors such as the composition of the digestate, application rates, and plant species. However, according to research data, adding digestate to the soil tends to increase the content of phenolic compounds and antioxidants in plants [29,36]. In our study, significant increases in total phenolic compounds begin to be seen when 15 percent or more of digestate is added to the peat substrate for seedling growth (Table 1). Research by [PERSON] et al. also shows Fattoria (poultry, cow, and sheep manure) and Uliva (olive waste and citrus pulp, with some addition of livestock manure and maize silage) digestates to increase TPC contents and suggests that these two digestates stimulated plant-resource reallocation to secondary metabolite production because of carbon and phenols in the constitution [25]. As the literature states, the accumulation of compounds exhibiting antioxidant activity increases as the fruit ripening proceeds [45]. This means that the overall ability of the fruit to neutralize free radicals may increase. This increase in antioxidant capacity is often associated with changes in the levels of specific antioxidants such as vitamin C, vitamin E, carotenoids, and phenolic compounds. Research shows that each antioxidant compound has a unique pattern of accumulation and degradation during the ripening process [36,46]. This tendency is present and visible in the results of this study (Tables 1-4). Also, the correlation test shows changing relationships between different antioxidant assays during fruit ripening (Table 6). FRAP, ABTS, and DPPH assays showed increased antioxidant activity from unripe to fully ripe fruit. Researchers, such as [PERSON] et al. [47], confirm the findings that show FRAP activity increases in later maturation stages of fruit.