Traditional fallows in Latin America

Traditional fallow systems of Latin America have not been extensively studi ed from either a socioeconomic or biophysical viewpoint. Only in the past d ecade have some of these systems - modified shifting cultivation in the Ama zon, the bracatinga (Mimosa scabrella) fallow of southeastern Brazil, the b abassu (Attalea spp.) system of the Amazon margins, and short bush fallows mostly for Phaseolus bean (the so-called 'frijol tapado') - received any at tention. Over the past century, traditional cultivators have adopted severa l legumes such as Mucuna spp., Lathyrus nigrivalis, Canavalia spp., and Sen na guatemalensis as green manures or managed fallows in food crop productio n systems, which have recently been the object of studies by social and bio logical scientists. Longer, monospecific fallows involving woody legumes ha ve been studied to varying degrees. The legumes include Senna guatemalensis , Mimosa tenuiflora, and Gliricidia sepium. Systems in which crop productio n is alternated with animal grazing of secondary vegetation include the 'ca atinga' of Northeast Brazil, the 'espinales' of Chile, the 'matorrales' of northern Mexico, and the 'chaco' of Argentina, Paraguay, and Bolivia. A cla ssification is proposed depending on the nature of the species (woody or no nwoody) and their composition (mono- or multispecies) and land management ( burned or not). Much work is still needed in more complete characterization , determination of economic importance and potential, understanding the rel ationships among components, studies of nutrient cycling, and verification of the effects of shorter fallow periods of these systems.