Crop diversification for weed management - Ecological Management of Agricultural Weeds - page 355

Figure 7.9 Density ofreadily germinable seeds in soils collected from fallows of
different ages in the Palcazu Valley,Peru.(Adapted from Staver,1991.)
seed bank, and are usually eliminated as weeds. If cropping is intensified
either by longer cropping periods, more frequent weeding, or greater crop
cover, tree regeneration is delayed (Staver, 1991). A balance exists between
crop management practices, especially weeding, and the rate at which tree
cover is re-established after cropping is discontinued.
To suppress the growth of herbaceous weeds and accelerate the rate at
which woody perennial species come to dominate a field,Staver (1989b) exam-
ined the effects of planting a combination of Inga edulis and Desmodium ovalifo-
lium into a cassava/plantain intercrop. Inga edulis is a fast-growing leguminous
tree adapted to high light conditions; Desmodium ovalifolium is a slow-growing,
woody, stoloniferous, shade-tolerant legume used for ground cover. Weed
growth was suppressed both by presence of I. edulis and increasing D. ovalifo -
lium cover (Staver, 1989 b ). The combination of I. edulis plus D. ovalifolium
increased woody biomass production and plantain yields,but had no effect on
cassava yields,compared with plots without the legumes.Three years after the
first clearing, fallow vegetation was cut and burned again and maize was
planted. Plots following I. edulis plus D. ovalifolium produced higher maize
yields and less weed biomass than those following natural fallow (C. Staver,
unpublished data).