Soil Mapping in Africa Breaks New Ground

Accurate knowledge of local and regional soil characteristics is essential for sustainable agricultural development, but the existing body of information about the conditions and trends of African soils is outdated and imprecise. Thus there is an urgent need for accurate, up-to-date and spatially-referenced soil information—in the form of accurate and comprehensive maps—to support agriculture in Africa.

Conventional soil mapping is limited in what it can communicate. It relies on polygons—often lines originally drawn in the field by soil surveyors— and the resulting image cannot fully express the complexity of soils in a landscape or be easily integrated into a global map. As a result these maps have only limited value in making land management decisions, among other limitations. The first world soil map—created in 1981 by the Food and Agriculture Organization (FAO) of the United Nations and the UN Educational, Scientific and Cultural Organization (UNESCO)—is still utilized today but is greatly limited by its low resolution (1:5 million scale). Other higher-resolution conventional soil maps (1:1 million scale) are also available, but for only part of the globe.

Using new technologies and methods including vastly improved satellite data and ground-based spectral measurements, new techniques in statistical modeling, major improvements in the collection and prediction of soil properties, and improvements in pixel displays, it is now possible to produce a high-resolution digital soil map for the entire world, at 100 times the resolution of existing soils maps. Beginning by mapping sub-Saharan Africa, a digital soils map is being developed under the auspices of the Africa Soil Information Service (AfSIS) and the GlobalSoilMap.net Consortium. The map will be based on a fine-resolution three-dimensional grid showing functional properties of soils. Accessible to a mixed audience of scientists, local farmers and policymakers, the digital soils map will provide up-to-date information for the mapping of soil conditions, set a baseline for monitoring changes, and provide options for soil and land management.

AfSIS is led by the International Center for Tropical Agriculture—Tropical Soil Biology and Fertility Institute (CIAT-TSBF) at the Earth Institute, Columbia University, and ISRIC—World Soil Information. It includes scientists from national agricultural centers and universities throughout Africa, including Tanzania, Malawi and Mali, where regional laboratories conduct soil sampling and spectral analysis as well to train local partners. The project also involves collaboration with national agricultural research stations in Kenya, Nigeria and many other countries in Africa that are working on soil sampling, setting up field trials, conducting laboratory analysis and producing soil property maps. GlobalSoilMap.net collaborators are from national environmental and agricultural research centers and academic institutions around the world.

As of February 2011, soil sampling has begun in 20 sentinel sites across Africa including Mali, Malawi, Tanzania, Ethiopia, Ghana, Nigeria, South Africa and Zambia. For more information, see the paper, “Digital Soil Map of the World.”

Project Leader: Markus Walsh of the Tropical Agriculture Program, in cooperation with the Center for International Earth Science Information Network

Fuente: The Earth Institute, Columbia University.