## 3 Results and Discussion
### Impact of Agricultural Droughts on Grain Yield  
According to the identification of dry years in each region and for wheat and barley crops, the yield reduction for these years was calculated by averaging the 4 years identified in each region for each of the three approaches used (Tables 2 and 3). In drought years, the Spanish regions of CL and CM (Table 2) suffered a significant decrease in crop yields, which was evident in all cases. The average yield reduction in both \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Month Period**} & \multicolumn{2}{c}{**CL**} & \multicolumn{2}{c}{**CM**} \\ \cline{2-5}  & **Wheat** & **Barley** & **Wheat** & **Barley** \\ \hline M & 32.8 & 28.8 & 28.5 & 33.7 \\
2M & 34.9 & 32.2 & 31.5 & 33.9 \\
3M & 34.9 & 32.2 & 8.4 & 34.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average percentage of yield reduction in drought years in Castilla y León (CL) and Castilla-La Mancha (CM) for wheat and barley and for the three criteria (M, 2M and 3M). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Month Period**} & \multicolumn{2}{c}{**BY**} & \multicolumn{2}{c}{**NS**} & \multicolumn{2}{c}{**NW**} \\ \cline{2-5}  & **Wheat** & **Barley** & **Wheat** & **Barley** & **Wheat** & **Barley** \\ \hline M & \(-11.57\) & \(-11.38\) & \(1.31\) & \(3.69\) & \(2.85\) & \(-0.33\) \\
2M & \(-0.09\) & \(4.78\) & \(2.90\) & \(-0.79\) & \(1.88\) & \(4.41\) \\
3M & \(0.82\) & \(-2.49\) & \(11.80\) & \(16.18\) & \(-4.62\) & \(1.35\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Average percentage of yield reduction in drought years in Bayern (BY), Nordrhein-Westfalen (NW) and Niedersachsen (NS) for wheat and barley and for the three criteria (M, 2M and 3M). crops was greater than 30%, which demonstrates the importance of soil water in the root zone for wheat and barley yields [39]. These results are in agreement with the evidence obtained by the authors of [123], confirming that in semiarid agricultural areas, the most important limiting factor for crop productivity is water stress caused by reduced soil water availability and, therefore, agricultural drought. Comparing the two regions, a greater reduction is observed for wheat in CL and for barley in CM. However, the difference in crop reduction in both regions is small, usually less than 5%. There is an interesting debate as to whether wheat or barley is better adapted to drought. Some authors [124; 125] found better adaptation of barley to drought conditions, displaying a better yield potential than wheat in the Mediterranean basin. In contrast, several studies [126; 127] did not find consistent differences between the yields of the two crops. In general, in the present work, in both regions and crops, a similar yield reduction of between 29% and 35% predominates. These reductions are larger than those obtained in the projection of [128] for winter wheat in Spain, with a predicted average yield decrease of 21% by the end of the 21 st century. These results highlight the susceptibility of rainfed crops to the increasing intensity of soil drought and warn of the severe impacts on crop yields that are already occurring. It is well known that the Mediterranean area is among the most vulnerable regions to climate change, and this is likely to worsen in the future [129]. Indeed, climate models project a decrease in SM and an increase in the duration and intensity of droughts in the Mediterranean region [3; 17]. Therefore, this observed reduction in crop yields could be exacerbated in the future, and in the face of growing global food needs, this finding is of great concern and may aggravate the global food crisis [130; 131]. In the case of Germany, there is notable variability in cereal yield variations in all three regions (Table 3). In BY, an increase in yield was observed, reaching 11% when the critical month approach was applied for both crops. In contrast, the NS and NW regions showed mostly yield reductions.