Interactions entre le soja "Glycine max" (L) Merrill et l'adventice "Acanthospermum hispidum" DC

Résumé

A field experiment was conducted in 1990-1991 at the Institut de Developpement Rural, Brazzaville-Congo (4°10'S, 15°20'E; 313m elevation; 17km south of Brazzaville), to evaluate interactions between soybean, Glycine max (L.) Merrill and bristly starbur, Acanthospermum hispidum DC, by using replacement series. The design consisted of three association densities (6, 12 and 24 plants/m2), with five percentages (100:0, 75:25, 50:50, 25:75, and 0:100) of each species per density. Soybean dry matter production and soybean yield decreased as the proportion of A. hispidum increased (Tables 1 and 2). Replacement diagrams showed that both soybean and A. hispidum production levels were larger than theoretically expected (Figure 2). Production indices showed that soybean markedly decreased as the proportion of A. hispidum increased (Table 3). We conclude that the two plant species clearly share the same resources without antagonism, with each tapping common resources.