DOI: 10.7910/dvn/phiqxv
title: Digital map of chemical fertility of soils of continental Ecuador

description: &lt;p&gt;Digital tools are transforming and accelerating innovation in agriculture. Digital soil maps are important tools for better-informed decision-making supported by data and science. The maps permit addressing site-specific strategies needed by fertile and healthy soils to minimize the impacts of land use change, increase productivity without generating degradation and deforestation, and to deal with climate challenges..&lt;br /&gt;
To contribute to the diagnosis, monitoring, and control of soil degradation in Ecuador, the digital Map of Chemical Fertility of Soils of continental Ecuador and continuous soil properties maps of organic matter (%), pH (Un), available phosphorus (mg/kg), available potassium (cmol/kg), cation exchange capacity (cmol/kg), base sum (cmol/kg), base saturation (%), electrical conductivity (dS/m), clay (%) and sand (%) were developed by using digital soil mapping approaches, 13,552 soil profile data, and 46 environmental covariables..&lt;br /&gt;
The maps generated in this service are also available, &lt;a href="http://geoportal.agricultura.gob.ec/geonetwork/srv/eng/catalog.search;jsessionid=957DBF6F3C169DE18D6DEA1BEA90B0E8#/metadata/1a636166-4a14-4b31-88b3-7d417dd0ea54" target="_blank"&gt;the Geoportal of the Ministry of Agriculture and Livestock of Ecuador&lt;/a&gt;.&lt;br /&gt;.
description: Methodology: <br>
The continuous soil maps of organic matter (%), pH (Un), available phosphorus (mg/kg), available potassium (cmol/kg), cation exchange capacity (cmol/kg), base sum (cmol/kg), base saturation (%), electrical conductivity (dS/m), clay (%) and sand (%) were developed based on digital soil mapping approaches (McBratney et al., 2003).
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These maps were the inputs to develop the Digital Map of Chemical Fertility of the Soils of continental Ecuador Sánchez-Ortega (1996). For more details on the methodologies used in this development, go to the technical report.
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The main phases of the process are described as follows:
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1. Collection, cleaning, and standardization of field data: The information on soil profiles was obtained from the database harmonized by the MAG and the University of Almería (Spain), 2022, collected at the national level through the MAG, IEE, and SENPLADES during the period 2009-2015. The data was harmonized obtaining a total of 13,552 profiles, which were standardized to a depth of 0-30 cm for use in mapping the fertility of Ecuadorian soils. 
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2. Collection and harmonization of explanatory covariates: A total of 42 environmental covariates related to climate, geology, topography, soils, vegetation cover, etc., were collected from official and freely accessible sources in the country (e.g. MAG, Google Earth Engine, Worldclim). These covariates were harmonized to a same format (raster), projection system (WGS84-UTM17S), spatial resolution (30m), and national limits. 
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3. Selection of covariates: The selection of the most appropriate covariates for the prediction of each property was made based on the theory of soil formation and the VSURF algorithm. 
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4. Spatial modeling: Random forest (cross-validation k = 10) was used as a machine learning algorithm for the spatial prediction (spatial resolution = 30m) of the chemical properties of continental Ecuadorian soils (pH, organic matter, phosphorus, potassium, saturation, and sums of bases, electrical conductivity and cation exchange capacity). The validation of the models was carried out through the root mean square error (RMSE), the mean absolute error (MAE), and the coefficient of determination (R2). The uncertainty assessment was performed through the quantile regression forest (QRF). 
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5. Chemical fertility map (Classification): Following the methodology used by Sánchez-Ortega (1996) and IGAC (2021), the classification and assignment of scores (according to their relevance in terms of fertility) to the chemical properties according to the interpretation ranges was carried out: (Very high = 5, high = 4, medium = 3, low = 2, very low = 1). Subsequently, the digital map of the chemical fertility of continental Ecuador was calculated and classified as a result of the weighted sum of the previously classified chemical properties, adding those areas of low and very low fertility of soil with cangahuas in the central and northern of the Sierra and high salinity areas on the coast.