Exploring the contribution of farmers to local digital soil mapping
Résumé
In spite of their fine resolution, the Digital Soil Mapping (DSM) products that are now available at global or national scale do not provide accurate representations of the local soil patterns as required by the end-users acting at local level (Lemercier et al, 2022). A local Digital Soil mapping approach that would model separately the local soil variations within smaller areas (watersheds, municipalities) should be preferable. However, this approach requires investments in quantitative spatial soil sampling that are most often inaccessible for a local user. As an alternative, we explored in this study the possibility of using the soil knowledge of the local farmers (Richelle et al, 2018) for applying local DSM approaches. The approach was applied in the Gopalapura village (Karnataka, India).
Elicitation of the soil knowledge of the farmers had two steps. First a local soil typology was co-built by a group of 27 farmers and the soil surveyors following the approach described in Lagacherie et al, (2021). Second the farmers were asked to locate each soil type within the area of interest. The output was a set of sites labelled with a soil type. This new farmer soil data was compared with a very detailed (1/12,500) soil map. This allowed to evaluate the ability of farmer soil data to discriminate and further map three qualitative soil properties (textural class, gravel class, and soil map). Finally, a DSM model was built to map the farmer soil types over the Gopalapura village territory
The results showed good to moderate agreements between soil survey and farmer soil information according to soil properties. Beyond the expected increase of performance of soil properties