## 4 Conclusions  
The impact of agricultural drought on wheat and barley crops in the main cereal-growing regions of Spain and Germany during the 2001-2020 period was analyzed. In general, the results of all the analyses carried out in this study show the importance of SM in cereals, especially in the months of the reproductive and ripening phases of the crops. Moreover, with respect to the three approaches studied, the results obtained showed similar patterns. Therefore, it can be stated that the three criteria were useful for the identification of drought years and for the calculation of yield loss. \begin{table}
\begin{tabular}{c 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{2-7}  & **Wheat** & **Barley** & **Wheat** & **Barley** & **Wheat** & **Barley** \\ \hline M & ND & ND & 4.67 & 12.02 & 6.16 & 11.87 \\
2M & 3.26 & 12.30 & 5.60 & 10.36 & 2.70 & 12.78 \\
3M & 5.75 & 12.10 & 10.63 & 21.57 & 0.96 & 11.59 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average percentage of yield reduction in the drought year 2011 in Bayern (BY), Nordrhein-Westfalen (NW) and Niedersachsen (NS) for wheat and barley and for the three criteria used (M, 2M and 3M). ND means not a drought year. The analysis of the GPP and LAI variables revealed similar behaviors in water-limited environments and the inverse in energy-limited environments, showing the influence of soil water content on the development of these variables. The use of SM anomalies evidenced their suitability for the identification of years with agricultural drought, in agreement with previous findings. Furthermore, a cluster of drought years was observed in the second decade of study in Germany, which is a clear indicator of warning in terms of SM deficit in areas where this variable is not the main constraint. As expected, in water-constrained areas, a considerable reduction in crop yields has been observed, exceeding 30% yield reduction, because of agricultural drought. Unexpectedly, in regions located in energy-constrained areas, where water is not the main limiting factor, a singular yield reduction of around 5% has been observed for both crops. Thus, the results suggest that, in the face of increased droughts, the worsening of cereal yield losses is likely, which will increase notably in southern regions, as is happening in Spain. Similarly, Germany, where the SM was not considered a constraint until now, is starting to show increasing water stress that may lead to unprecedented reductions in cereal yields. This finding has important implications for agriculture, as it was proven that in recent years, in areas where water was not the main limiting factor, it is now having detrimental effects on crop yields. Although the yield decrease detected in the German regions shows moderate values, it is an indicator of change in environmental conditions and will have negative consequences on agricultural production. Indeed, in view of climate change impacts, the results obtained warn against a new uncertain scenario for crop yields. This likely transformation suggests that in areas where SM has not yet been a limiting factor, the situation can reverse and lead to a significant decrease in cereal yields. This possible scenario could be similar to that currently being observed in Spanish regions, where yields have declined by more than 30% in drought years over the last two decades due to soil water deficits. The results of this study are of interest for adaptation and/or mitigation strategies to cope with these detrimental impacts on crop yields due to agricultural drought. The initial idea for this research was conceived by [PERSON]. The different datasets were prepared by [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON], who also collected all the results. All authors have equally contributed to the analysis and the interpretation of the results. The first manuscript was prepared by [PERSON], in collaboration with the other authors.