## 3 Results and Discussion
BAs react much more quickly in soil than lime, leading to a more substantial increase in pH, although this effect tends to be relatively short-lived [13]. As demonstrated by [PERSON] et al. (2017), pH changes in the topsoil exhibit the greatest dynamics within the first 50 days following BA application. It has also been noted that the application of BAs can cause extreme fluctuations in pH, particularly in the top layer of the soil (pH = 11.0-4.4); therefore, this should be considered in realistic assessments of their impact on pH changes and the associated soil properties [40]. The content of various salts in the soil can be determined indirectly by measuring their concentration in the soil solution through electrolytic conductivity (EC). Soils for the cultivation of most crops should not exhibit signs of salinity, as salinity leads to soil degradation and reduced plant productivity [41; 42]. Soil EC is influenced by several factors, including soil moisture, ion content, clay particle content, and bulk density [43]. Based on EC values, the following salinity classification is adopted: 0-2 dS m\({}^{-1}\) for non-saline soils, 2-4 dS m\({}^{-1}\) for slightly saline soils, 4-8 dS m\({}^{-1}\) for saline soils, 8-16 dS m\({}^{-1}\) for strongly saline soils, and >16 dS m\({}^{-1}\) for very strongly saline soils [44]. According to this classification, the analyzed soil in the 0-30 cm layer was characterized by low salinity (EC = 68 \(\mu\)s cm\({}^{-1}\)) before the experiment (Table 1). The use of BAs in the present study did not affect the soil salinity class. The data indicate that the average EC values, depending on the experimental variant, showed considerable variability, ranging from 43.5 to 141.0 \(\mu\)s cm\({}^{-1}\) (Figure 3). The changes in soil EC during the study period significantly depended on the species of the cultivated plants only (\(p\) < 0.001) (Table 2). In general, the soil under winter rape cultivation exhibited higher average EC values than the original soil, and this pattern was consistent across all the experimental treatments. The comparison of the individual experimental treatments revealed that, regardless of the fertilization applied, the average EC value was lower in the soil where potatoes were grown (Figure 3). Despite the increase in EC, the use of BAs did not result in a change in the soil salinity class. After three years of using BAs, salinity remained low regardless of the species of the cultivated plant. This indicates that the concentration of salts present in the soil was at a level tolerated by all the species grown. The results obtained in this study differ from those reported by [PERSON] and [PERSON] (1999), who found a significant increase in EC values, which peaked at 2.5 mS  
Figure 2: Effect of ashes from biomass combustion on soil HAC under the cultivation of various crop species (mean \(\pm\) SE). Mean \(\pm\) standard error; identical superscripts (a, b, c, d) denote non-significant differences between means according to the post hoc [PERSON]’s HSD test. cm\({}^{-1}\), indicating a high degree of soil salinization due to the use of BAs. Such salinization can be harmful to various plant species, particularly woody plants. Simultaneously, these studies show that the increase in soil salinity caused by BA application follows a similar trend to that of pH [45]. In a study conducted by [PERSON] et al. (2018), it was also found that the application of BAs led to a fourfold increase in EC values in the surface layer of the soil, compared to the control. This increase in salinity was attributed to the high sodium content in the applied ash [46]. Similarly, [PERSON] et al. (2021) and [PERSON] et al. (2018) reported increased soil salinity as a result of using wood biomass ash [37; 47]. Due to their high content of alkaline components, BAs are characterized by elevated electrolytic conductivity, which can be detrimental to many plant species. The BAs used in our research were characterized by high salinity, with an EC value of 8.81 mS cm\({}^{-1}\).