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Please consult the frequently asked questions below. If you don’t find what you are looking for, you can send us your question.

  • What information on soil properties have you made available?

    We’ve created predictions for a number of different chemical, physical and agronomic soil properties. Where we’ve predicted numerical values, we have also included estimates of uncertainty. For categorical data and some other third-party layers, no uncertainty measurements are available.

    See below for information on the data available in iSDAsoil.

    Property Extraction / Measurement information Unit Available Depths (cm) Geospatial Resolution (m) Theme Uncertainty Available? Model Accuracy (R-square) RMSE Attribution
    Land Cover (2015 – 2019) N/A % 0 100 Agronomy information No N/A N/A Yes Landcover images courtesy of Copernicus Land Monitoring Service
    Cropland (2015 – 2019) N/A % 0 100 Agronomy information No N/A N/A Yes Cropland images courtesy of Copernicus Land Monitoring Service
    Slope Angle N/A degree 0 30 Physical soil properties and landscape No N/A N/A
    Fertility Capability Classification N/A None 0-50 30 Agronomy information No N/A N/A
    USDA Texture Class USDA 12 class system None 0-20, 20-50 30 Physical soil properties and landscape No N/A N/A
    Clay content Various % 0-20, 20-50 30 Physical soil properties and landscape Yes 0.746 9.6
    Bulk density, <2mm fraction Various g/cc 0-20, 20-50 30 Physical soil properties and landscape Yes 0.819 126
    Aluminium, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.881* 0.321*
    Carbon, total Various g/kg 0-20, 20-50 30 Soil properties Yes 0.794* 0.291*
    Calcium, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.840* 0.543*
    Effective Cation Exchange Capacity Mehlich-3 cmol(+)/kg 0-20, 20-50 30 Chemical soil properties Yes 0.754* 0.417*
    Iron, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.817* 0.235*
    Potassium, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.773* 0.509*
    Magnesium, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.815* 0.497*
    Nitrogen, total Measured by Total combustion g/kg 0-20, 20-50 30 Chemical soil properties Yes 0.732* 0.197*
    Carbon, organic Various g/kg 0-20, 20-50 30 Chemical soil properties Yes 0.791* 0.369*
    Phosphorus, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.486* 0.707*
    Sulphur, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.548* 0.384*
    Zinc, extractable Mehlich-3 ppm 0-20, 20-50 30 Soil nutrients Yes 0.711* 0.375*
    pH 1:1 Soil-Water Suspension 0-20, 20-50 30 Chemical soil properties Yes 0.818 0.459
    Sand content Various % 0-20, 20-50 30 Physical soil properties and landscape Yes 0.736 13.7
    Silt content Various % 0-20, 20-50 30 Physical soil properties and landscape Yes 0.64 8.92
    Stone content Various % 0-20, 20-50 30 Physical soil properties and landscape Yes 0.709* 0.803*
    Depth to Bedrock Estimated from soil profile data cm 0-200 30 Physical soil properties and landscape Yes 0.429 41.3
    Land Cover (2015 – 2019)
    Extraction / Measurement information N/A
    Unit %
    Available Depths (cm) 0
    Geospatial Resolution (m) 100
    Theme Agronomy information
    Uncertainty Available? No
    Model Accuracy (R-square) N/A
    RMSE N/A
    Attribution Yes Landcover images courtesy of Copernicus Land Monitoring Service
    Cropland (2015 – 2019)
    Extraction / Measurement information N/A
    Unit %
    Available Depths (cm) 0
    Geospatial Resolution (m) 100
    Theme Agronomy information
    Uncertainty Available? No
    Model Accuracy (R-square) N/A
    RMSE N/A
    Attribution Yes Cropland images courtesy of Copernicus Land Monitoring Service
    Slope Angle
    Extraction / Measurement information N/A
    Unit degree
    Available Depths (cm) 0
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? No
    Model Accuracy (R-square) N/A
    RMSE N/A
    Fertility Capability Classification
    Extraction / Measurement information N/A
    Unit None
    Available Depths (cm) 0-50
    Geospatial Resolution (m) 30
    Theme Agronomy information
    Uncertainty Available? No
    Model Accuracy (R-square) N/A
    RMSE N/A
    USDA Texture Class
    Extraction / Measurement information USDA 12 class system
    Unit None
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? No
    Model Accuracy (R-square) N/A
    RMSE N/A
    Clay content
    Extraction / Measurement information Various
    Unit %
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.746
    RMSE 9.6
    Bulk density, <2mm fraction
    Extraction / Measurement information Various
    Unit g/cc
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.819
    RMSE 126
    Aluminium, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.881*
    RMSE 0.321*
    Carbon, total
    Extraction / Measurement information Various
    Unit g/kg
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil properties
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.794*
    RMSE 0.291*
    Calcium, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.840*
    RMSE 0.543*
    Effective Cation Exchange Capacity
    Extraction / Measurement information Mehlich-3
    Unit cmol(+)/kg
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Chemical soil properties
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.754*
    RMSE 0.417*
    Iron, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.817*
    RMSE 0.235*
    Potassium, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.773*
    RMSE 0.509*
    Magnesium, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.815*
    RMSE 0.497*
    Nitrogen, total
    Extraction / Measurement information Measured by Total combustion
    Unit g/kg
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Chemical soil properties
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.732*
    RMSE 0.197*
    Carbon, organic
    Extraction / Measurement information Various
    Unit g/kg
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Chemical soil properties
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.791*
    RMSE 0.369*
    Phosphorus, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.486*
    RMSE 0.707*
    Sulphur, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.548*
    RMSE 0.384*
    Zinc, extractable
    Extraction / Measurement information Mehlich-3
    Unit ppm
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Soil nutrients
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.711*
    RMSE 0.375*
    pH
    Extraction / Measurement information 1:1 Soil-Water Suspension
    Unit
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Chemical soil properties
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.818
    RMSE 0.459
    Sand content
    Extraction / Measurement information Various
    Unit %
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.736
    RMSE 13.7
    Silt content
    Extraction / Measurement information Various
    Unit %
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.64
    RMSE 8.92
    Stone content
    Extraction / Measurement information Various
    Unit %
    Available Depths (cm) 0-20, 20-50
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.709*
    RMSE 0.803*
    Depth to Bedrock
    Extraction / Measurement information Estimated from soil profile data
    Unit cm
    Available Depths (cm) 0-200
    Geospatial Resolution (m) 30
    Theme Physical soil properties and landscape
    Uncertainty Available? Yes
    Model Accuracy (R-square) 0.429
    RMSE 41.3

    *indicates data were log-scaled before modelling

  • How were these maps made?

    A detailed description of our workflow is available on the technical information page.

  • How can I contribute data to help improve the maps?

    We are keen to create maps that are constantly improving. If you’re aware of some legacy soil data or have been involved in data collection, please let us know. We’ll be happy to integrate it and provide acknowledgment.

    Contact us to share information about your dataset, and we’ll be in touch.

  • How can I report a problem with the data?

    You can get in touch via email at our Contact us page

  • What locations have you predicted soil properties for?

    We have covered all areas suitable for agriculture across Africa. For the majority of properties, we have not made predictions for locations classed as deserts or water bodies. You can check the map to see where predictions were made for each layer.

  • What is the fertility capability classification (FCC) layer?

    We’ve created a partial implementation of the soil FCC framework, as developed by Sanchez et al. (2013), in order to assess soil quality in the tropics. The idea behind this layer is to inform users about possible constraints that may need to be addressed in order to make soil productive and fertile. As data was not available for all soil constraints, we’ve produced a subset of the total constraints, with minor modifications:

    Shallow: Depth to bedrock less than 50cm
    Gravel: Stone content more than 10%
    Slope: slope angle more than 15°

    High erosion risk: Textual discontinuity (any of the following):

    • USDA Texture class of 0-20cm layer = Sand or Loamy Sand, and USDA Texture class of 20-50cm layer = Sandy clay, Silty Clay or Clay
    • USDA Texture class of 0-20cm layer = Sand, Loamy sand, Sandy loam, Loam, Silty loam, Silt, or Sandy clay loam, and USDA Texture class of 20-50cm layer = Clay Loam, Silty clay loam, Sandy Clay, Silty Clay, or Clay

    High erosion risk: Shallow depth (any of the following):

    • USDA Texture class of 0-20cm layer = Clay Loam, Silty clay loam, Sandy Clay, Silty Clay or Clay, and depth to bedrock less than 50cm
    • USDA Texture class of 0-20cm layer = Sand, Loamy sand, Sandy loam, Loam, Silty loam, Silt or Sandy clay loam, and depth to bedrock less than 50cm
    • USDA Texture class of 0-20cm layer = Sand or Loamy Sand, and depth to bedrock depth less than 50cm

    High erosion risk: Steep slope: slope more than 30°
    Sulfidic: pH of 0-20cm or 20-50cm layer less than 3.5
    Aluminium toxicity: Organic carbon less than 120g/kg in 0-20 or 20-50cm layer, and pH between 3.5 and 5.5 in 0-20cm or 20-50cm layer
    Calcareous: pH more than 7.3 in 0-20 or 20-50cm layer
    Low potassium reserves: extractable potassium less than 78ppm, and pH less than 7.5 in 0-20cm or 20-50cm layer
    High leaching potential: Cation exchange capacity less than 4cmol/kg in 0-20cm or 20-50cm layer
    No constraints: if none of the above are satisfied. Other constraints may be present that we have not mapped.

  • How accurate is the data?

    The majority of the soil property layers were created using machine learning and are therefore predictions. For each prediction we also include an estimate of the prediction error, or uncertainty – i.e. how certain the algorithms are that the predicted value is correct.

    For users of the iSDAsoil API, uncertainty is returned at 3 different confidence intervals, representing 50%, 68% (1 standard deviation) and 90% quantile intervals. These confidence intervals are defined using an upper and lower boundary value, which captures the percentage chance that the predicted value falls between these two values. The closer the upper and lower boundary values to the predicted value, the more certain the prediction, with 50% representing the most stringent threshold, and 90% representing the least.

  • What does “Variability” mean on the maps?

    The “Variability” displayed on the map refers to 1 standard deviation on either side of the predicted value, capturing 68% of the total variability of the prediction (see previous question for explanation of confidence intervals).

  • In which projection are the maps available?

    EPSG:3857, a variant of the Mercator projection popular with web applications.

  • Can I search a location by latitude and longitude?

    Yes, the API accepts lat/lon queries. You can also search on the iSDAsoil map by providing the lat,lon as comma-separated values.

  • Is bulk data download available?

    We have made the majority of layers and covariates available for bulk download via Zenodo. We also plan to add iSDAsoil data to Google Earth Engine – please sign up to our mailing list to keep abreast of updates.

  • How is the data licenced?

    All data are freely available under a Creative Commons Attribution 4.0 International License.

  • I have another question that wasn’t answered here: how do I get in touch?

    If you have any another questions, you can contact us via email.

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