Growth and yield of Bactris gasipaes and Pourouma cecropiaefolia in swidden fields of Amazon Indians, Colombia

Abstract

As part of a programme to study fruit growing under shifting cultivation by Huitoto and Muinane Indians in the Amazon area, Colombia, a 3 month field study was devoted to pejibaye palms ( Bactris gasipaes) and Amazon tree grapes ( Pourouma cecropiaefolia). Growth and yield of palms and trees are compared in the first-cleared field (‘home garden’) which has a more permanent character than the swidden fields (‘chagras’) cleared in subsequent years. Measurements of palms and trees in 1–8-year-old chagras and home gardens were used to fit growth curves to the growth and yield data of the two species. Both species grew faster and yielded more in home gardens than in chagras. Amazon tree grapes in home gardens had a larger trunk girth, smaller tree height and a much greater number of living branches, shoots, leaves and bunches. The slender, poorly branched habit of the trees in chagras is attributed to fierce competition for light from the resurging forest. Pejibaye was much less affected by the environment, but still the numbers of leaves and bunches per palm were higher in the gardens. The height of the palms increased so fast that it is likely that for this species soil factors rather than light conditions were limiting. The methodology afforded valuable insights in growth and yield of the two species over the first 7 years in both crop environments, on the basis of a 3 month field study. However, palm girth measurements revealed that growing conditions in young and old home gardens had not been equal, invalidating a basic assumption of the methodology. Hence the fitted curves for both species in home gardens are not equivalent to growth curves of given set of trees over a number of years and no unbiased estimates of the differences between chagras and home gardens could be made. Extreme caution should be exercised in constructing ‘growth curves’ by combining data from trees of different age.