South Africa and Namibia, 2003

This workshop covered contrasting environments, from semi-arid Namibia to more humid regions of South Africa. Participants examined soils with strong climatic gradients, salinity issues, and variable horizon development. The community focused on classification challenges in drylands and transitional environments. Discussions emphasized the importance of clear diagnostic criteria and consistent field interpretation. The workshop contributed to refining WRB for arid and semi-arid regions.

It’s often referred to as the “Arid Soils Tour” .

On the occasion of the 50th anniversary of the Soil Science Socies of South Africa (SSSSA), a field tour was organized through the (semi-)arid parts of western South Africa and the coastal zone of Namibia. Twenty-eight participants joined this tour, coming from Australia, Belgium, Burkina Faso, Germany, Hungary, Italy, Namibia, the Netherlands, Russia, South Africa,Tar:r;ania, and the United States (see list of participants attached). Purpose of the tour was (l) to get better insight in the diversity of soils in (semi-)arid regions, (2) to study land use practices on these soils (irrigation, water harvesting, ripping), (3) to test the validity of .WRB, with special focus on Solonchaks, Gypsisols, Durisols, and Calcisols, and (4) to appraise possible harmonization between WRB and the USDA Soil Taxonomy.

Duration of the tour was ten days and the total distance covered was some 5000 km. After an initial get together at the University of Stellenbosch and a welcome address by the President of the SSSSA, Prof. Huyssteen, the group boarded three minibuses and two “bakkies” to set off nor1h. During the first part of the tour through the West and North Cape Provinces, mainly Durisols, exposed duripans or “dorbanke”, silcrete, ferricrete and calcrete were studied, as well as the (unexpectedly) high influence of ternites on soils in the semiaridpartsofthisregion. At Maanskloof Farm near Cihusdal three soils derived from wind-blown and colluvial deposits from Table Mountain sandstone were studied, all of which keyed out as Arenosols. Here a major discrepancy appeared between WRB and ST, because the clay illuviation features (lamellae) forced these soils into Ultisols in ST, recognizing the sandy character only at family level, wheras the sandy character in WRB is recognized at the highest (Arenosol) level. The discrepancy is also caused by the textural requirement for argic horizons in WRB, inherited from the Revised Legend of the Soil Map of the World, requiring at least 8oÀ clay, which does not occur in the ST definition of argillic horizon

The tour provided good insight into properties, variety and management aspects of the WRB group of Durisols, as well as those of typical desert soils as Glpsisols, Calcisols and Solonchaks. The need for rehning the qualifier level was demonstrated on several occasions, particularly in relation to the chemistry of precipitates (e’g. puffed vs. non-puffed Solonchaks, presence of dolomitic precipitates) as well as to morphological characteristics of hardpans, such as petrocalcic, petrogypsic and petroduric. Special attention has to be paid to those hardpans that are fragmented and which allow roots to penetrate into the subsoil, a condition that is presently not catered for in WRB. Proposals for refining will be considered by the WRB group if these are accompanied by good examples (descriptions, physicaVchemical data).

A negative aspect of the tour was the paucity in data and descriptions of the soils viewed. It must be emphasized to future organizers of WRB tours that soils to be studied need full field description according to FAO guidelines and that essential physical and chemical data are to be provided, in order to avoid fruitless discussions on wether a soil has e.g. a sandy loam or loamy sand texture.

Apart from this, the tour was well organized and the Stellenbosch University, in parlicular Freddie Ellis and Jan Lambrechts have to be complemented for a job well done. Many thanks go out as weli to the drivers of the vans and “bakkies” who brought us safely back to Stellenbosch.