The map shows the dominant soil and terrain constraints of land for low input farming conditions. The map was developed
within the IIASA/FAO GAEZ 2009 modelling framework.
It illustrates that soil nutrient availability is by far the most prevalent soil limitation in most regions, in particular
in the tropics, especially in large parts of Middle Africa and Central South America.
Soil and terrain constraints affecting agricultural production include:
• Nutrient availability: soil fertility level
• Nutrient retention capacity: capacity of the soil to retain nutrients against losses caused by leaching
• Rooting conditions: effective soil depth and volume, affecting rootability.
• Oxygen availability: drainage characteristics of soils affect oxygen availability to roots.
• Excess salts: saline and sodic soil conditions. Salinity inhibiting crop water uptake of the soil and affecting growth
and reducing yields. Sodicity causing sodium toxicity and affecting soil structure causing low soil permeability.
• Calcium carbonate and gypsum. Excess calcium carbonate causes micronutrient deficiencies and excess gypsum limits available
• Soil workability constraints: Soil conditions may cause physical hindrance to cultivation.
• Terrain slopes: topsoil erosion reduces soil depth, natural soil fertility and soil moisture.