Effect of cowpea ( Vigna unguiculata ) intercropping on weed biomass and maize ( Zea mays ) yield

Field experiments were conducted to investigate the influence of cowpea ( Vigna unguiculata ) density (0, 15 or 30 plants/m 2 ) 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/m 2 ) on weed biomass and maize crop yield. Results showed that increasing the maize density from 7.5 to 9 plants/m 2 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/m 2 , respectively. Under weed‐free conditions, an increase in maize density from 7.5 to 9 plants/m 2 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/m 2 and simultaneously intercropping with cowpea at a density of 30 plants/m 2 could be an appropriate control measure for weed suppression.