## 3 Results and Discussion
### Mycotoxins Occurrence
These toxins are primarily produced during and after the flowering stage (anthesis) to early grain-filling stages of cereals such as wheat, barley, and maize. Infection risk is highest when warm, wet, and humid conditions occur during flowering, as the fungi infect \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**N-Dose** & **Barley Variety** & **FB2** & **FB1 + FB2** & **T-2** & **HT-2** & **T-2 + HT-2** & **DON** & **15-AcDON** \\ \hline \multicolumn{2}{c}{Maximum levels for} & & & & & & & \\ mycotoxins in cereal grains 2 & - 3 & - 3 & - 4 & - 4 & 150 5 & 1000 6 & - 3 \\ \hline \multirow{4}{*}{60 kg N/ha} & Zoom & 17.80 & 17.80 & - & - & - & 121.42 & - \\  & Hobbit & - & - & - & - & - & 173.82 & - \\  & Galation & - & - & - & - & - & 224.51 & - \\  & Sandra & - & - & - & - & - & - & - \\ \hline \multirow{4}{*}{90 kg N/ha} & Zoom & - & - & - & - & - & 97.58 & - \\  & Hobbit & - & - & - & - & - & 289.62 & 16.56 \\  & Galation & - & - & \(<\)1 & \(<\)1 & 1.53 & 244.25 & 22.13 \\  & Sandra & - & - & - & - & - & - & - \\ \hline \multirow{4}{*}{120 kg N/ha} & Zoom & - & - & - & - & - & 201.38 & - \\  & Hobbit & - & - & - & - & - & 209.95 & 13.53 \\ \cline{1-1}  & Galation & - & - & - & - & - & 228.79 & 21.47 \\ \cline{1-1}  & Sandra & - & - & - & - & - & - & - \\ \hline \multirow{4}{*}{150 kg N/ha} & Zoom & - & - & - & - & - & 202.04 & - \\  & Hobbit & - & - & - & - & - & - & - \\ \cline{1-1}  & Galation & - & - & - & - & - & 273.20 & 20.58 \\ \cline{1-1}  & Sandra & - & - & - & - & - & 84.32 & - \\ \hline \hline \end{tabular}  
* Acc. to the Commission Regulation (EU) 2024/1022 of 8 April 2024 amending Regulation (EU) 2023/915 as regards maximum levels of deoxynivalenol in food [62].  
\end{table} 
Table 6: Mycotoxins occurrence (ug/kg) in grains of four barley varieties grown in different conditions of nitrogen fertilization (N-dose) in the controlled field trial in Poland 1.  
colonizing developing kernels. The fungi can continue to produce DON and 15-AcDON as the grain matures, especially if moist conditions persist up to harvest [67; 68]. In our study, during the experiment in May, when barley was earing, high rainfall was recorded, almost twice as high as the long-term average (Table 1). In this case, this could have been the reason for the presence of these mycotoxins in the grain. DON and 15-AcDON are commonly found in food and feed samples due to a combination of biological and stability factors. There is a notable prevalence of 15-AcDON-producing _Fusarium_ strains, with certain species, such as _F. graminearum_, primarily biosynthesizing 15-AcDON as an intermediate metabolite during the production of DON [69; 70]. This results in a higher natural occurrence of 15-AcDON compared to 3-AcDON in contaminated cereal grains [70]. Additionally, 15-AcDON often coexists with DON in grains, further increasing its detection frequency [71]. Stability during storage and processing also plays a crucial role; studies indicate that both DON and 15-AcDON demonstrate greater stability during grain storage than 3-AcDON, enhancing their durability and likelihood of detection [71]. Some authors point to the impact of nitrogen fertilization on the risk of mycotoxin contamination of cereal grains. In some cases, a higher risk of mycotoxin contamination has been associated with higher nitrogen fertilization rates during cultivation [29]. However, another study found that nitrogen fertilization reduced the _Fusarium_ mycotoxin content in barley grains, suggesting that well-supplied plants may be more resistant [30]. The studies investigating the impact of agricultural factors and practices on mycotoxin contamination indicate that high organic matter content in the soil and diverse crop rotations are linked to a lower risk of _Fusarium_ mycotoxin contamination, while high doses of mineral nitrogen fertilizers, overuse of certain fungicides and herbicides, and lack of crop rotation may increase the risk of contamination [31].