|An Afisol (Luvisol) soil derived from mudstone in Eastern Samar, Philippines|
|Selected properties of the major tropical soils (Jahn and Asio, 2006)|
- The tropics, the world’s largest ecological zone, have very high potential for plant growth but with soil limitations in vast areas.
- About one-third of the soils of the world are tropical soils. The most widespread are Ferralsols, Acrisols, Luvisols, Cambisols and Arenosols.
- The large proportion of Cambisols (Inceptisols) and Luvisols (Alfisols) in Southeast Asia reflects clearly the younger age of land surfaces and therefore the short duration of weathering processes.
- Some soils occur almost exclusively within the tropics. About 90% of the Ferralsols (Oxisols), 80% of the Nitisols (Oxisols/Ultisols), and 60% of the Acrisols (Ultisols) are situated in tropical regions.
- The major soil limitations or soil constraints are low cation exchange capacity, low base saturation (low pH, high Al-saturation) and high P retention. They are most widespread in South America, Africa and Southeast Asia (in decreasing order based on area).
- Physical constraints like high groundwater table, air deficiency and low soil depth are of lesser significance but govern special requirements for soil management in specific landscapes.
- Due to severe chemical limitations, proper management of nutrients is the main challenge for effective land use systems in the tropics.
- Internal and external fluxes of nutrients are different among soil types and different among tropical landscapes. These have to be considered in ecological land use systems.
- To conserve the stock of organic matter in tropical soils (and to increase it in degraded soils), biomass productivity will be a key point for ecological land use systems.
- To enable policy-makers as well as land users to establish sustainable and ecological land use systems in the tropics, more precise soil maps and soil information are needed.