## 3 Results and Discussion
Despite these elevated EC values in BAs, their application over the three years did not result in a change in the soil salinity class. As mentioned earlier, BAs contain a substantial amount of alkaline components, which can positively influence changes in soil pH and acidity but may also lead to excessive salinization [20; 21]. Therefore, the impact of BAs on the content of Ca, Mg, K, and Na was analyzed. These elements are not only important plant nutrients but also directly affect changes in soil properties, including pH and EC [48]. Among the analyzed elements, K and Ca were the most abundant in the BAs used in the experiment, reflecting the original composition of the type of biomass burned, as noted in the literature [49]. The content of Mg and Na was also consistent with the information presented in the literature regarding certain types of BAs [50]. The relatively high concentrations of Ca, Mg, K, and Na in the BAs utilized in the experiment generally led to an increase in the levels of these elements in the soil surface layer, with the extent of this effect varying according to the species of the cultivated plant (Tables 1 and 3). As shown in Table 3, the content of Ca, Mg, K, and Na in the soil after the application of BAs varied, depending on the experimental variant and the cultivated plant species. Overall, during the three years of the experiment, the average content of Ca, Mg, and K was lower in the soil under spring barley and winter rapeseed cultivation, compared to the control. However, these changes were statistically insignificant, especially after applying the highest doses of BAs. In the case of potatoes, a reverse relationship was  
Figure 3: Effect of ashes from biomass combustion on soil EC under the cultivation of various crop species (mean \(\pm\) SE). Mean \(\pm\) standard error; identical superscripts (a, b, c) denote non-significant differences between means according to the post hoc [PERSON]’s HSD test. observed; in this experimental variant, the average contents of Ca, Mg, and generally K were higher following the application of BAs. Conversely, compared to the control, the average Na content was higher in the soil in all the experimental variants under barley and potato cultivation, while it was generally lower in the soil under rapeseed cultivation. As mentioned earlier, K was the most abundant element in the BAs; however, the soil application of BAs did not result in a significant increase in K levels in the soil, as in the case of the other elements, particularly Ca and Mg. This may be due to several reasons. Firstly, K is an element that easily dissolves and migrates to groundwater. In a study on the solubility of major elements in ashes from biomass combustion, [PERSON] et al. (1994) found that K dissolves very quickly (over 50% of the total content), while Ca and Mg dissolve relatively quickly as the ash/water ratio increases and P remains practically insoluble [51]. In field conditions during the experiment, meteorological conditions were found to be an important factor influencing the K content in the soil, its release from BAs, and the growth and development of cultivated plant species. According to the data presented in Table S2, the individual years of the experiment varied in this regard. The highest rainfall amounts (792.4 mm) were noted in the second year of the study. In contrast, the third year recorded the lowest rainfall total of 610.3 mm. As a result, the distribution of nutrients introduced into the soil with BAs may have differed from year to year. In the years with lower rainfall, the solubility of the constituents in BAs might have been lower than in the second year of the experiment characterized by higher precipitation. With more rainfall, the greatest solubility of the components in BAs, particularly in the case of K, can be assumed. For this reason, no significant increase in the K content in the soil after the application of BAs was generally observed.