# Monitoring Rainfed Alfafa Growth in Semiarid Agrosystems Using Sentinel-2 Imagery
## 4 Conclusions  
In this work, we explored the suitability of Sentinel-2 imagery for the monitoring of rainfed alfalfa crop establishment in the semiarid Bardenas Reales area. For this purpose, 172 in situ FVC samples were compared with different VI values derived from Sentinel-2 imagery. In situ images of an area of one square meter were processed using a maximum likelihood supervised algorithm in order to calculate the FVC of each sample. The non-destructive methodology of this study represents an advantage compared to other studies that used a destructive methodology, where estimations were only possible during the harvesting period [14; 57]. Furthermore, FVC estimation using multitemporal Sentinel-2 images makes it possible to monitor crop growth, assisting farmers in making well-informed management decisions [13].  
Sentinel-2 imagery is useful for assessing the rainfed alfalfa establishment in Bardenas Reales. The NDVI showed the best correlation (\(R^{2}\) = 0.727) between FVC and VI at the parcel level.  
We detected that the parcels in zone III, located to the south at a higher altitude (540 m), exhibited the best altitude for the optimum development of alfalfa crop compared to the plots in the north and middle zone of Bardenas Reales. Therefore, we conclude that NDVI values derived from Sentinel-2 images are suitable for monitoring rainfed alfalfa plots in a semiarid area, such as Bardenas Reales, and allows for good decisions to be made in traditional practices such as crop and cattle feeding management.  
The improvements in Sentinel-2 imagery in terms of accessibility (i.e., free), spectral range, and spatial and temporal resolution make it a very interesting option for crop monitoring, especially over high-extension areas. Sentinel-2 effectivity estimated alfalfa FVC in Bardenas Reales at the parcel level, reporting a good accuracy, and may help farmersmonitor rainfed alfalfa growth in semiarid areas. Accurate observation of alfalfa crop yields will enhance decision making on agricultural management and ecosystem services for transhumant cattle feeding management in the semiarid agrosystem of Bardenas Reales.  
The following are available online at [[https://www.mdpi.com/article/10.3390/rs13224719/s1](https://www.mdpi.com/article/10.3390/rs13224719/s1)]([https://www.mdpi.com/article/10.3390/rs13224719/s1](https://www.mdpi.com/article/10.3390/rs13224719/s1)).  
Conceptualization, E.M.G., A.U. and A.E.; methodology, E.M.G., M.G.-A. and A.E.; software, M.G.-A. and A.E.; validation, E.M.G., M.G.-A. and A.E.; formal analysis, A.E.; investigation, E.M.G., M.G.-A., A.U. and A.E.; resources, A.U.; data curation, A.E.; writing--original draft preparation, A.E.; writing--review and editing, E.M.G. and M.G.-A.; visualization, E.M.G., M.G.-A., A.U. and A.E.; supervision, E.M.G. and M.G.-A.; project administration, E.M.G.; funding acquisition, E.M.G. and M.G.-A. All authors have read and agreed to the published version of the manuscript.  
[PERSON] was supported by a predoctoral fellowship from the Government of Navarra. This work was supported by the knowledge transfer contract 2018020023 UPNA-Bardenas Reales Committee with partial collaboration of the project PID2019-107386 RB-I00/AEI/10.13039/501100011033 (MINECO/FEDER-UE).  
Data Availability Statement: Data is contained within the article or Supplementary Material.  
We would like to thank the technicians at the Bardenas Reales Interpretation Centre for their technical assistance, [PERSON] for his expert advice regarding the in situ samplings of vegetation cover in the Bardenas Reales area and and [PERSON] for critical reading and helpful suggestions during the writing of the manuscript.  
The authors declare that they have no known competing financial interests or personal relationship that could have influenced the work reported in this paper.  
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