Demand-Driven Technologies for Sustainable Maize ... - IITA

176of cowpea, than in the farmers’ practice of continuous sole cropping ofmaize for three years. Intercropped maize recorded 19.9% higher grainyield than the continuously sole cropped maize.DiscussionResults of this study have demonstrated the potential of appropriatesoybean and cowpea cultivars to reduce Striga parasitism in maize. Italso demonstrated the potential of maize-cowpea intercrops to controlStriga. The two legume cultivars used were able to reduce Strigaparasitism in the rotation systems.Intercropping maize with cowpea reduced the density of emergedStriga plants. This reduction may be attributed to shading effects fromthe cowpea canopy. Carson (1989) reported a positive relationshipbetween soil temperatures and the density of emerged Striga plantsunder groundnut (Arachis hypogaea L.) intercropped with sorghum.He found that the temperature at a soil depth of 10 cm at 6–7 weeksafter sorghum emergence was about 2 o C lower in sorghum rows andthat Striga density at the time of harvesting sorghum was reduced by60-70% in the treatment with sorghum and groundnut in the samerow. Carsky et al. (1994) reported that the number of mature capsulebearingStriga plants was low when the cowpea groundcover washigh in a sorghum-cowpea intercrop. This suggests that any spatialarrangement that increases cowpea groundcover at the base of maizeor sorghum can reduce the density of mature Striga. Carsky et al.(1994), therefore, concluded that in the long term, this might reducethe Striga seed bank, provided no importation of Striga seed to thefi eld was allowed. They also found no signifi cant reduction in sorghumyield by intercropping sorghum with cowpea. In the present study,intercropping cowpea with maize reduced maize yield by 47% despitethe reduction in the number of emerged Striga plants. This could bedue to competition from the cowpea. This corroborates the fi ndings ofKureh et al. (2000) and Kuchinda et al. (2003). Maize and sorghumappear to have different responses to competition effects from othercrops in intercropping systems. Maize has a shorter maturity periodthan sorghum. Hence, sorghum may recover from the effects ofintercropping long after the cowpea has been harvested.Several studies have shown a signifi cant reduction in Strigaparasitism in cropping systems that include intercropping androtations (Carsky et al. 1994; 2000; Schulz et al. 2003; Kuchinda etal. 2003). Several other mechanisms can be suggested to explain thereduction of Striga damage when maize is intercropped or rotated withlegume trap-crops. In addition to shading out Striga in intercroppingsystems, the cowpea or soybean has been shown to stimulate thegermination of Striga without acting as hosts (Carsky et al. 1994;