AfSIS-GYGA functional soil information of Sub-Saharan Africa (RZ-PAWHC SSA version 01 0)
Root Zone Plant-Available Water Holding Capacity of the Sub-Saharan Africa soil
The development of the root zone plant-available water holding capacity of the Sub-Saharan Africa soil builds on previous achievements made by the AfSIS project. The Africa Soil Profiles database (AfSP) was expanded to 18,500 sites and these legacy soil data were combined with newly sampled topsoil data for 9,600 clustered sites (AfSS). Soil property maps for SSA were updated, using the expanded soil dataset and revised geo-statistical modelling, which resulted in revised soil property maps with enhanced accuracy at 250-m resolution over 2-m depth (www.isric.org/data/afsoilgrids250m). The maps are available for primary soil properties, both physical (drainage, depth, gravel, texture, bulk density) and biochemical (pH, CEC, exchangeable bases and acidity, organic carbon, nitrogen). Next, functional soil properties are derived, including soil water retention (including plant-available water holding capacity) assessed by using pedotransfer functions (Wösten et al., 2013; www.isric.org/content/soil-hydraulic-information-river-basin-studies-semi-arid-regions) and root zone depth, for maize, assessed by rules and thresholds established together with agronomists of the GYGA project (including depth of soil, depth of aerated soil and depth to restrictive rootability index (LRI) based on porosity, textural adequacy, acidity, alkalinity, sodicity, salinity and toxicity). The preliminary results are reviewed, the primary maps corrected for bulk density, exchangeable Na, electric conductivity and drainage, and the final results produced at 1km resolution for each depth interval and aggregated over the root zone depth. This functional soil information is used by the GYGA project to model and estimate water-limited yield potentials and yield gaps in ten Sub-Saharan countries. The collaborative work developed a consistent and updateable high-resolution soil information framework for agronomic modelling in support to defining improved agronomic management practices in SSA.
The first version of the gridded dataset is released here as RZ-PAWHC SSA v.1.0. Available are 1) the input data, including soil profiles data -queried from the AfSP database- and the primary soil property maps resampled at 1km resolution, 2) the intermediate results per depth interval including the plant available water holding capacity and the Limiting Rootability Indices and 3) the final results including the root zone depth, the factors limiting root zone depth and the plant-available water holding capacity aggregated over the root zone depth (in mm). The dataset including metadata is available for download at a FTP server (see column at the right side) and also as a Web Mapping Service (http://wms4.isric.org/geoserver/afsis_gyga/wms) and Web Coverage Service (http://wms4.isric.org/geoserver/afsis_gyga/wcs) for direct use in a GIS environment. A technical report on the RZ-PAWHC SSA is included describing the methods and results and including metadata describing the gridded maps.
Citation: J.G.B. Leenaars, T. Hengl, M. Ruiperez Gonzalez, J. Mendes de Jesus, G.B.M. Heuvelink, J. Wolf, L. van Bussel, L. Claessens, H. Yang and K.G. Cassman, 2015. Root zone plant-available water holding capacity of the Sub-Saharan Africa soil, version 1.0. Gridded functional soil information (dataset RZ-PAWHC SSA v. 1.0). ISRIC report 2015/02. Collaboration project of Africa Soil Information Service (AfSIS) and Global Yield Gap and Water Productivity Atlas (GYGA). ISRIC - World Soil Information, Wageningen.