Abstract

Field experiments were conducted to investigate the influence of cowpea (Vigna unguiculata) density (0, 15 or 30 plants/m2) and sowing date (15 days prior to maize sowing or simultaneously with maize), and of maize (Zea mays) planting density (7.5 or 9 plants/m2) on weed biomass and maize crop yield. Results showed that increasing the maize density from 7.5 to 9 plants/m2 reduced the weed biomass by 21.5%. Furthermore, cowpea acted as a living mulch, reducing weed biomass by up to 45.5% and 39.6% when intercropped with maize at a density of 7.5 and 9 plants/m2, respectively. Under weed-free conditions, an increase in maize density from 7.5 to 9 plants/m2 resulted in maize grain yield increasing from 8.92 to 9.40 t/ha; however, the addition of cowpea only increased the maize grain yield by about 4.2%, on average, under these conditions. By contrast, under weed-infested conditions, there was a large decrease in maize grain yield (up to 32%), but intercropping with cowpea reduced this to only a 16% decrease. Under weed-free conditions, there was no effect of sowing date on maize grain yield; however, under weed-infested conditions, yield was greater on the second sowing date. Thus, it is concluded that the planting of maize at a density of 9 plants/m2 and simultaneously intercropping with cowpea at a density of 30 plants/m2 could be an appropriate control measure for weed suppression. Keywords: integrated weed management; sowing date; plant density; cover crop; living mulch