Sentinel-2 Recognition of Uncovered and Plastic Covered Agricultural Soil

Medium resolution satellite data, such as Sentinel-2 of the Copernicus programme, offer
great new opportunities for the agricultural sector, and provide insights on soil surface characteristics
and their management. Soil monitoring requires a high-quality dataset of uncovered and plastic
covered agricultural soil. We developed a methodology to identify uncovered soil pixels in agricultural
parcels during seedbed preparation and considered the impacts of clouds and shadows,
vegetation cover, and artificial covers, such as those of greenhouses and plastic mulch films. We
preserved the spatial and temporal integrity of parcels in the process and analysed spectral anomalies
and their sources. The approach is based on freely available tools, namely Google Earth Engine
and R Programming packages. We tested the methodology on the northern region of Belgium,
which is characterised by small, fragmented parcels. We selected a period between mid-April to
end-May, when active agricultural management practices leave the soil bare in preparation for the
main cropping season. The spectral angle mapper was used to identify soil covered by non-plastic
greenhouses or temporary soil covers, such as plastic mulch films. The effect of underlying soil on
temporary covers was considered. The retrogressive plastic greenhouse index was used for detecting
plastic greenhouses. The result was a high quality dataset of potential bare uncovered agricultural
soil that allows further soil surface characterisation. This offered an improved understanding of the
use of artificial covers, their spatial distribution, and their corresponding crops during the considered
period. Artificial covers occurred most frequently in maize parcels. The approach resulted in
precision values exceeding 0.9 for the detection of temporary covers and non-plastic greenhouses
and a sensitivity value exceeding 0.95 for non-plastic and plastic greenhouses.