## 4 Discussion  
Overall, the GI assay results reveal intricate interactions among utilized bio-based fertilizing products, dilution rates, and plant types. The lower GI observed in concentrated digested sludge mixture's water-extracts suggests the presence of phytotoxic factors, with their impact diminishing as dilution ratio increases. Notably, lettuce seeds exhibit a higher sensitivity compared to wheat seeds when exposed to concentrated extracts of digested sludge mixture. This finding aligns with existing literature indicating a general lower sensitivity to toxicity in seeds from root crops, cereals, and legumes when compared to seeds of leafy plants, which is attributed to the higher food reserve content in the former [52; 53]. In contrast, biochar and digestate water-extracts show an opposite trend, with higher GI in concentrated extracts gradually decreasing with increasing dilution rates, reaching values comparable to the control. This pattern suggests the presence of phyto-stimulatory factors in more concentrated water-extracts, positively influencing germination process and subsequent plant growth. Manure water-extracts also show phyto-stimulant effects on lettuce and wheat seeds, although a distinct sensitivity of these two plants is evident. Generally, phytotoxicity results from a combination of factors, including phytotoxins, salinity, high ammonium concentration, and heavy metals, which can delay seed germination and inhibit plant growth [6; 54]. In addition, cytotoxic effects can also occur. In a study by [PERSON] et al. [55] the same biochar sample's organic extracts show cytotoxic effect at concentration of 1%, while biochar and digestates water-extracts do not show toxic effects. Therefore, it is crucial to consider not only nutrient concentrations but also potential risks of metal accumulation, soil salinization, and cyto- and phyto-toxic effects, when applying EOMs to soil, comprehending their specific impacts on different types of crops. In our mesocosm experiment, a higher biochar rate (10%) significantly increases soil salinity, C and N contents, potentially posing risks of phytotoxicity effects for more sensitive crops. On the positive side, the observed phyto-stimulatory effects of biochar and digestate water extracts highlight their potential benefits attributed to the presence of plant nutrients, growth stimulants, or even phytochrome-like substances [20; 36]. Furthermore, downstream processing technologies could reduce the risks for phytotoxicity effects of EOMs. Our results clearly indicate the effectiveness of AD and pyrolysis in reducing inhibitory factors, making the digestate and biochar suitable for use as fertilizer and/or soil amendment. The stability of organic matter is crucial in preventing phyto-toxicity, with AD significantly contributing to the stabilization of organic material by partially degrading organic matter [37] and organic pollutants derived from feedstocks and reducing salinity [56]. The sewage sludge in this study's mixture is digested, but evidently it does not reach the same stability as cattle manure-based digestate likely due to its origin and presence, for example, of organic contaminants [55]. However, a critical consideration in utilizing digestate is ensuring that it does not harbor harmful microorganisms, particularly pathogens, which could pose a risk of infection spread [16; 31]. We observe a significant increase in the relative abundance of Clostrtidiaceae in digestate-amended soil, which underscores the impact of AD by-products on the soil microbial community. This finding reflects the resilience and functional importance of the Clostrtidiaceae microbial group in AD systems, as indicated by various studies [57; 58; 59; 60]. However, it also raises concerns about potential contamination risks. _Clostridium_ bacteria are common in animal manure and naturally occur in soils at relatively high number.