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Copernicus Sentinel-2 data to estimate soil organic carbon in croplands

03 May 2019

One of the main threats for soil degradation is the decline of soil organic carbon—the Copernicus Sentinel-2 satellites are currently being exploited to monitor soil conditions in croplands, in turn supporting the Common Agricultural Policy of the European Union.

Soil Organic Carbon (SOC) is a key property for soil quality and food production, as  recognised by the European Union, who considers its decline in European soils as one of the main threats for soil degradation.

The Sentinel-2 mission of the European Union's Copernicus programme is based on a constellation of two identical satellites that together cover all Earth's land surfaces, large islands, inland and coastal waters every five days at the equator.

The mission mainly provides information for agricultural and forestry practices and for helping manage food security.

The revisit time of just five days, along with the mission's range of spectral bands mean that changes in soil condition can be more easily monitored.

The span of 13 spectral bands, from the visible and the near infrared to the shortwave infrared at different spatial resolutions ranging from 10 to 60 m, takes land and soil monitoring to an unprecedented level.

Funded by BELSPO (the Belgian Federal Science Policy Office), the PROSOIL project team, led by the Earth and Life Institute of the UCLouvain, evaluated the capability of Copernicus Sentinel-2 data for SOC estimation and mapping, in three regions of Belgium, Germany and Luxembourg.

These areas were chosen because of presenting different soil characteristics and a considerable variability of SOC content.

The PROSOIL team investigated the capability of Copernicus Sentinel-2 bare soil images to map the organic carbon content of the topsoil in croplands. They compared the Copernicus Sentinel-2 results with those obtained using airborne hyperspectral data with higher spatial resolution.

The results highlighted that the spatial resolution of Copernicus Sentinel-2 is adequate to describe SOC variability both at field and regional scale and the prediction accuracy obtained by Copernicus Sentinel-2 data is very similar to that retrieved by airborne hyperspectral data.

The level of detail of the SOC maps obtained by Copernicus Sentinel-2 images can support both environmental monitoring related to global warming and precision agriculture strategies.

In this context, the  accuracy of the SOC maps is affected by the calibration dataset, which should be representative of the investigated area while at the same time including, as much as possible, the full range of SOC values.

The PROSOIL team successfully tested the capability of the Copernicus Sentinel-2 spectral data to select sampling location, providing soil samples with a large variability in terms of SOC content. This is possible using selection algorithms that exploited the good correlation between SOC content and most of the Copernicus Sentinel-2 bands.

PhD researcher at ILVO (Flanders Research Institute for Agriculture, Fisheries and Food), Fabio Castaldi, says, "The availability and the short revisit time of the Copernicus Sentinel-2 images entail a huge amount of satellite data that can increase the possibility to have more reliable images during the years. This is especially important in the context of soil imaging spectroscopy, for the narrow time window in which we can find bare soil in croplands."

About the Copernicus Sentinels

The Copernicus Sentinels are a fleet of dedicated EU-owned satellites, designed to deliver the wealth of data and imagery that are central to the European Union's Copernicus environmental programme.

The European Commission leads and coordinates this programme, to improve the management of the environment, safeguarding lives every day. ESA is in charge of the space component, responsible for developing the family of Copernicus Sentinel satellites on behalf of the European Union and ensuring the flow of data for the Copernicus services, while the operations of the Copernicus Sentinels have been entrusted to ESA and EUMETSAT.

Acknowledgements

Castaldi, F., Chabrillat, S., van Wesemael, B., Castaldi, F., Chabrillat, S., van Wesemael, B., 2019. Sampling Strategies for Soil Property Mapping Using Multispectral Sentinel-2 and Hyperspectral EnMAP Satellite Data. Remote Sens. 11, 309. https://doi.org/10.3390/rs11030309

Castaldi, F., Hueni, A., Chabrillat, S., Ward, K., Buttafuoco, G., Bomans, B., Vreys, K., Brell, M., van Wesemael, B., 2019. Evaluating the capability of the Sentinel 2 data for soil organic carbon prediction in croplands. ISPRS J. Photogramm. Remote Sens. 147, 267–282. https://doi.org/10.1016/J.ISPRSJPRS.2018.11.026