FLORISTIC DIVERSITY AND ECOLOGICAL STRUCTURE OF THE WEEDS ASSOCIATED WITH COWPEA CULTIVATION (VIGNA UNGUICULATA L. WALP.) IN SMALLHOLDER FARMING SYSTEMS IN THE DEPARTMENT OF MBOUR (SENEGAL)

Abstract

Cowpea (Vigna unguiculata) is a major food legume of Sahelian rainfed farming systems, whose productivity remains limited by weed pressure that is poorly documented at the crop scale. This study aims to characterize the floristic diversity and ecological structure of the weeds associated with cowpea in smallholder farming systems, in the department of Mbour. Ten floristic surveys were carried out in smallholder farming conditions, then analyzed by hierarchical ascending classification (Pearson index), complemented by the biological and chorological spectra. The inventory recorded 37 species distributed across 10 botanical families, very largely dominated by the Poaceae (40.5%), ahead of the Fabaceae, Cyperaceae, Rubiaceae and Malvaceae. A core of 10 constant species, present in 90 to 100% of the surveys, notably including Cyperus rotundus, Digitaria ciliaris and Spermacoce verticillata, structure most of the assemblage alongside a majority of occasional species. The flora is dominated by therophytes (73.0%) and by species with a wide biogeographic distribution (pantropical and African), reflecting a heavily disturbed environment. These results call for priority to be given, in integrated management strategies, to the core of ten constant species, in particular the geophyte Cyperus rotundus, and for weeding interventions to be timed to the emergence peaks of annual species.