This study aimed to determine the period of weed coexistence with three cowpea cultivars (Vigna unguiculata) in the lowlands of the state of Amazonas, Brazil. Cowpea was sown in October 2007 under the conventional system. The experimental design consisted of randomized blocks with four replications in split-plots. The plots consisted of eleven periods of weed coexistence with cowpea at 0, 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70 days after sowing. Following these periods, weeds were manually removed every week. The cultivars EV x 91-2E-2, BR IPEAN BR8 V69, and BR8 Caldeirão were located in the split-plots. The interference of the weeds throughout the cowpea life cycle reduced final stand, number of pods per plant, and weight of 1,000 grains. The productivity of cultivars EV x 91-2E-2, BR8 BR8 Caldeirão and BR IPEAN V69 was reduced by 59, 78, 68.18 and 90.18%, respectively. The period before interference was from 0 to 5 days after sowing for cultivar BR IPEAN V69, and from 0 to 6 and 71 days for cultivars BR8 Caldeirão and EV x 91-2E-2, respectively.
competition; weed community; Vigna unguiculata
