Traditional fallow systems of the Americas

Six neotropical traditional fallow systems are described: 1) enriched fallows of the Amazon, 2) Babassu palm (Orbignya phalerata Mart.) forests of central and northern Brazil, 3) bracatinga (Mimosa scabrella Benth) improved fallow of southeastern Brazil, 4) carbon negro (Mimosa tenuiflora Willd.) fallow of the wet-dry zone of Mesoamerica, 5) frijolillo (Senna guatemalensis Donn. Smith) of high-elevation zones in southern Honduras, and 6) caragra (Lippia torresii) fallow of humid zones of Costa Rica.These systems include both biologically and economically enriched fallows. Some (e.g., the enriched fallows of the Amazon) require a considerable degree of human intervention, while others (e.g., the bracatinga and carbon negro fallows) seem to form with little human encouragement, following the burn in shifting cultivation systems. Some of the systems (e.g., frijolillo and caragra) are quite site-specific and have a limited distribution; others (e.g., babassu, bracatinga, and carbon negro) occur over large areas and could be adapted to considerable areas in the Americas. As economic analyses are generally lacking, it is unclear what benefits would be achieved from a wider use of these systems. Most of the biologically enriched fallows seem able to maintain low yields of food crops at low input levels. Some of the economically enriched fallows seem able to produce higher economic returns.