Abstract
Traditional Amazonian farmers ( caboclos) along the Xingu River near Altamira, Pará, Brazil, practice shifting cultivation using fallow periods (periods during which cultivated areas are temporarily abandoned and invaded by secondary forest) which they consider necessary to restore soil nutrients and control weeds and insect pests. At the end of the growing season, maize production was measured in the farmers' fields in randomly selected 9-m 2 quadrats. Yield was significantly higher in agricultural plots derived from secondary forest ( n = 11) than from old growth (‘virgin’) forest ( n = 11). Yield on plots derived from mature secondary forest (11–30 yr old; n = 4) was also significantly higher than that on plots derived from young secondary forest (3–10 yr old; n = 7) and ‘virgin’ forest. A significant positive relationship was encountered between length of fallow period and maize yield over the range of fallow ages studied (3–30 yr).
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