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Mapping of tank silt application using Sentinel-2 images over the Berambadi catchment (India)

Gomez, C and Dharumarajan, S and Lagacherie, P and Riotte, J and Ferrant, S and Sekhar, M and Ruiz, L (2021) Mapping of tank silt application using Sentinel-2 images over the Berambadi catchment (India). In: Geoderma Regional, 25 .

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Official URL: https://doi.org/10.1016/j.geodrs.2021.e00389


Mapping soil properties is becoming more and more challenging due to the increase in anthropogenic modification of the landscape, calling for new methods to identify these changes. A striking example of anthropogenic modifications of soil properties is the widespread practice in South India of applying large quantities of silt from dry river dams (or �tanks�) to agricultural fields. Whereas several studies have demonstrated the interest of tank silt for soil fertility, no assessment of the actual extent of this age-old traditional practice exists. Over South-Indian pedological context, this practice is characterized by an application of black-colored tank silt to red-colored soils such as Ferralsols. The objective of this work was to evaluate the usefulness of Sentinel-2 images for mapping tank silt applications, hypothesizing that observed changes in soil surface color can be a proxy for tank silt application. We used data collected in a cultivated watershed in South India including 217 soil surface samples characterized in terms of Munsell color. We used two Sentinel-2 images acquired on February and April 2017. The surface soil color over each Sentinel-2 image was classified into two soil types (�Black� and �Red� soils). A change of soil color from �Red� in February 2017 to �Black� in April 2017 was attributed to tank silt application. Soil color changes were analyzed accounting for possible surface soil moisture changes. The proposed methodology was based on a well-balanced Calibration data created from the initial imbalanced Calibration dataset thanks to the Synthetic Minority Over-sampling Technique (SMOTE) methodology, coupled to the Cost-Sensitive Classification And Regression Trees (Cost-Sensitive CART) algorithm. To estimate the uncertainties of i) the two-class classification at each date and ii) the change of soil color from �Red� to �Black�, a bootstrap procedure was used providing fifty two-class classifications for each Sentinel-2 image. The results showed that 1) the CART method allowed to classify the �Red� and �Black� soil with correct overall accuracy from both Sentinel-2 images, 2) the tank silt application was identified over 202 fields and 3) the soil color changes were not related to a surface soil moisture change between both dates. With the actual availability of the Sentinel-2 and the past availability of the LANDSAT satellite imageries, this study may open a way toward a simple and accurate method for delivering tank silt application mapping and so to study and possibly quantify retroactively this farmer practice. © 2021 Elsevier B.V.

Item Type: Journal Article
Publication: Geoderma Regional
Publisher: Elsevier B.V.
Additional Information: The copyright for this article belongs to Elsevier B.V.
Department/Centre: Division of Mechanical Sciences > Civil Engineering
Date Deposited: 14 Jul 2021 06:38
Last Modified: 14 Jul 2021 06:38
URI: http://eprints.iisc.ac.in/id/eprint/68786

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