A case of study of land surface phenology for CAP management: Using Sentinel-2 data to obtain phenometrics for winter cereals in Andalusia, Spain

Abstract

The launch of the Copernicus Sentinel-2 mission offered new insights for the management of the European Common Agrarian Policy (CAP). Sentinel-2 provides information at a spatial and temporal resolution of 10 m and 5 days, respectively. However, this unprecedented time series of high resolution satellite imagery requires from approaches to extract meaningful agronomical information and reduce dimensionality. This could be the case of land surface phenology, which consists in estimating key phenometrics related to agronomical events from time series of vegetation indices (VIs). Knowing the dynamics of crop phenology is essential for the correct monitoring of CAP. We used EVI2 (Enhanced Vegetation Index 2) time series of Sentinel-2 data for the period 2018-2020. EVI2 is a VI widely used as an indicator of plant vigour, that avoids saturation in regions with high biomass. Double Logistic smoothing method was used to fill the gaps caused by the lack of images due to cloud presence or sensor failures. We selected plots of durum and common wheat, sorghum, barley and triticale according to the Geographical Information System for the CAP (GISCAP-CAP) declarations in Andalusia, Spain. The phenometrics extracted were start of the season (SOS), middle of the season (MOS), end of the season (EOS), their respective values of EVI2, and length of the season (LOS) (EOS-SOS). The aim of this study is to characterise the phenology of different winter cereals, through the extraction of phenometrics, and to evaluate whether these latter measures can serve to distinguish them. Results show that the response is quite similar between all of them, except sorghum. Common wheat shows the earliest SOS, followed by barley, durum wheat, triticale and sorghum. Common wheat shows the earliest EOS, followed by durum wheat, barley, triticale and sorghum.