INTERACTIONS BETWEEN NÉRÉ (PARKIA BIGLOBOSA) AND UNDER-PLANTED SORGHUM IN A PARKLAND SYSTEM IN BURKINA FASO

A farmer's intercropping system of white sorghum (Sorghum bicolor) and néré (Parkia biglobosa) was studied in Burkina Faso. In quadrats in three differing zones of tree influence, full sun (open field), semi-shade (under the edge of the tree crown) and full shade (under the crown), tree morphology and associated sorghum growth were recorded together with micro-meterological parameters. Mean photosynthetic photon flux density (PFD) was reduced to 51 and 26% of full sun levels, in the semi-shaded and fully shaded quadrats respectively. Soil temperature and moisture were also recorded. In the season studied, the principal effect of the trees on the crop was competition for light. For plants in full shade, total shoot and panicle mass were halved compared with the crop in full sun. However, plants in semi-shade were able to compensate for decreased PFD almost entirely. Measurable compensatory effects were decreased rate of leaf senescence, greater partitioning of resources into leaf production, and larger, thinner leaf laminae. It was concluded that the current farmers' practice of sowing under the crowns of trees produced a worthwhile, if somewhat reduced, crop yield, and that socially, economically and ecologically the sorghum–néré parkland system was worth retaining.