Abstract
Soil organic carbon (SOC) loss is one of the main causes of soil degradation in croplands. Thus, spatial and temporal monitoring of SOC is extremely important, both from the environmental and economic perspective. In this regard, the high temporal, spatial, and spectral resolution of the Sentinel-2 data can be exploited for monitoring SOC contents in the topsoil of croplands. In this study, we aim to test the effect of the threshold for a spectral index linked to soil moisture and crop residues on the performance of SOC prediction models using the Multi-Spectral Instrument (MSI) Sentinel-2 and the European Land Use/cover Area frame Statistical survey (LUCAS) topsoil database. The LUCAS spectral data resampled according to MSI/Sentinel-2 bands, which were used to build SOC prediction models combining pairs of the bands. The SOC models were applied to a Sentinel-2 image acquired in North-Eastern Germany after removing the pixels characterized by clouds and green vegetation. Then, we tested different thresholds of the Normalized Burn Ratio 2 (NBR2) index in order to mask moist soil pixels and those with dry vegetation and crop residues. The model accuracy was tested on an independent validation database and the best ratio of performance to deviation (RPD) was obtained using the average between bands B6 and B5 (Red-Edge Carbon Index: RE-CI) (RPD: 4.4) and between B4 and B5 (Red-Red-Edge Carbon Index: RRE-CI) (RPD: 2.9) for a very low NBR2 threshold (0.05). Employing a higher NBR2 tolerance (higher NBR2 values), the mapped area increases to the detriment of the validation accuracy. The proposed approach allowed us to accurately map SOC over a large area exploiting the LUCAS spectral library and, thus, avoid a new ad hoc field campaign. Moreover, the threshold for selecting the bare soil pixels can be tuned, according to the goal of the survey. The quality of the SOC map for each tolerance level can be judged based on the figures of merit of the model.
Highlights
Since the onset of agriculture, soils have lost their organic carbon to such an extent that the soil functions of many croplands are threatened
We tested the effect of the threshold for a spectral index linked to soil moisture and crop residues on the performance of soil organic carbon (SOC) prediction models in croplands using the European Land Use/cover Area frame Statistical survey (LUCAS) database and Sentinel-2 data
The resampling procedure of the LUCAS spectra according the Multi-Spectral Instrument (MSI)/Sentintel-2 bands allowed pointing out the strong correlation between the reflectance in the short wave infrared (SWIR) region and SOC content
Summary
Since the onset of agriculture, soils have lost their organic carbon to such an extent that the soil functions of many croplands are threatened. The Voluntary Guidelines for Sustainable Soil Management published by Intergovernmental Technical Panel on Soils [2] clearly indicated the loss of SOC as one of the main causes of soil degradation and lay down a set of good practices to enhance the soil organic matter content. These practices will be used as guidelines for cross-compliance rules for common agricultural Policy (CAP) in the European Union related to the good agricultural and environmental condition (GAEC) of the land for the period post-2020 [3]. The continuous spatial and temporal monitoring of the organic carbon content in agricultural soils becomes extremely important, from the environmental perspective, and in economic terms to ensure that the beneficiaries of the CAP respect their cross-compliance obligations
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
