Spectral monitoring of cattle slurry and digestate spreading on wheat crop at the field scale (Nouzilly, France)

International audience

English. A better knowledge of soil management, especially organic amendment practices, appears to be key, not only for modelling their soil C dynamics but also to characterize soil surface condition for the purpose of satellite-based mapping of topsoil soil organic carbon content (Vaudour et al., 2022). A previous study dealt with cattle manure and green waste compost spread on bare soil, and found several spectral indices (named EOMI1 to 4) enabling to characterize such spreading events (Dodin et al., 2021). However, little is known about the spectral characteristics of exogeneous organic matter (EOM) in liquid form, such as pig slurry and digestates, and this especially when EOM is spread over emerging crop (Dodin et al., 2022). This study aimed to spectrally monitor spreading events through a field experiment carried out on emerging wheat in March-April 2022 in the INRAE farm of Nouzilly (Touraine, France). Field reflectance spectra over the range 400—2500 nm were simulated into Sentinel-2 (S-2) spectra. Five S-2 satellite images were acquired close to spreading events. Vegetation coverage was assessed using photographs taken in the field and the CanEye® software of INRAE. Then, in order to discriminate between treatments, the time series of spectral indices (EOMI, NBR2, EVI, NDVI) either derived from field or from satellite were analysed through several multivariate approaches of Ascending Hierarchical Clustering (AHC). The AHC results obtained from the five EOM indices (EOMI1, 2, 3, 4 and NBR2) divided by EVI for all spectral samples in the field experiment lead to four classes, successfully discriminating between levels of EOM application. Our results suggest the capability of S-2 imagery to monitor spreading events over emerging vegetation.ReferencesVaudour E., Gholizadeh, A., Castaldi, F., Saberioon, M., Borůvka, L., Urbina-Salazar, D., Fouad, Y., Arrouays, D., Richer-de-Forges, A.C., Biney, J., Wetterlind, J., Van Wesemael, B., 2022. Satellite Imagery to Map Topsoil Organic Carbon Content over Cultivated Areas: An Overview. Remote Sensing 14, 2917. https://doi.org/10.3390/rs14122917Dodin, M., Smith, H.D., Levavasseur, F., Hadjar, D., Houot, S., Vaudour, E., 2021. Potential of Sentinel-2 Satellite Images for Monitoring Green Waste Compost and Manure Amendments in Temperate Cropland 13 1616. doi :10.3390/rs13091616Dodin, M., Levavasseur, F., Savoie, A., Martin, L., Staub, C., Foulon, J., Vaudour, E., 2022. Potential of Sentinel-2 Satellite Images for Monitoring Digestate and Slurry spreading in Temperate Cropland, SOM 2022 Seoul, South Korea, oral presentation.