Deficiencies and toxicities of trace elements and micronutrients in tropical soils: Limitations of knowledge and future research needs

This article reviews present knowledge concerning deficiencies and toxicities of trace elements and micronutrients in tropical soils. The myth that all tropical soils are highly leached and nutrient-poor is challenged. Continuing use of the term ''laterite'' by ecologists and geologists is criticized and adoption of ''plinthite'' is urged. The trace element content of plinthite and its possible influence on micronutrient availability are described. Micronutrient limitations of tropical agriculture are related to soil type and formation, and the special problem of aluminum toxicity in acid soils is discussed in both agricultural and ecological contexts. Studies of micronutrient cycling in tropical forests or savannas are needed to supplement the emerging picture of the complexities of major element cycles in these ecosystems. Interest in gold mining has stimulated studies of the element in tropical soils, and mining of the metal is leading to mercury pollution in Amazonia.