Soil fertility management in indigenous homegardens of Central Amazonia, Brazil

Homegardens in an upland forest area in the Kwata-Laranjal indigenous territory (state of Amazonas, central Amazonia) were studied to assess how their management contributes to soil fertility. The characteristics of the homegarden soil were compared with those of adjacent primary and secondary forest, at soil depth of 0-10, 10-20 and 20-30 cm. Significant homegarden effects were observed, which raised pH (H2O) (4.3-4.4 at 0-20 cm) and phosphorus content (5-14 mg kg(-1) at 0-30 cm); and decreased the content of calcium (0.1 cmol(c) kg(-1) at 20-30 cm). At the same time, levels observed in homegardens for aluminum (3.0-3.2 cmol(c) kg(-1)), organic carbon (11-13 g kg(-1)), calcium (0.24-0.38 cmol(c) kg(-1) at 0-20 cm), magnesium (0.08-0.20 cmol(c) kg(-1)) and potassium (0.06-0.10 cmol(c) kg(-1)) were not significantly different from those of primary and secondary forest. These results indicate that the management of these homegardens contributes to maintain or increase soil fertility. However, feasible management options to increase the content of these soils in carbon, calcium, magnesium and potassium are highly desirable.