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

278(Emechebe et al. 1991) may have increased S. gesnerioides buildupas both S. hermonthica and S. gesnerioides were prevalent in somecereal-cowpea intercrops. This suggests that the two species can coexisteven under intercropping. The rotation systems used by farmersmay not be effective for Striga control because not all legumes arecapable of inducing suicidal germination of Striga. Different strategiesshould, therefore, be developed to control the two Striga species. Therewas high incidence of S. densifl ora in pearl millet fi elds though grassspecies in fallow and weedy rice fi elds were alternative hosts of thespecies. The implication is that growing late maturing varieties of pearlmillet after fallow may increase the Striga buildup in the soil. S. asperawas found mainly attacking upland rice. Its economic importance willincrease with the expansion of rice production in these areas.The higher level of S. hermonthica infestation in the SS may beattributed to the dominance of sorghum-based cropping system,lower total rainfall, poor weed management and low application ofnutrients such as nitrogen and organic manure (PROSAB 2004).The predominance of the maize-based cropping system in the morehumid ecologies probably reduced the level of Striga infestation. Efron(1993) reported that Striga emergence counts were generally lowerin maize than sorghum fi elds. Weber et al. (1995) also suggestedthat maize could be used to reduce Striga seed bank in the soil.Better crop management practices, such as fertilizer application andtimely weeding that are recommended for maize probably helped inreducing Striga seed bank in the soil. The prolonged growth duration,inadequate fertilization and after-harvest sprouts that support seedproduction by Striga plants may have contributed to a greater Strigabuildup in sorghum-based than maize-based cropping systems.The relatively higher infestation of cowpea fi elds by S. gesnerioidesin the NGS and SS may be attributed to continuous cropping ofcowpea and increased land use intensifi cation. The fact that mostStriga sp. hot spots were recorded in compound farms gives furthersupport to the notion that increased land use intensifi cation due toincreased pressure on land increases Striga infestation. This is becausecowpea, which is mainly grown in these two ecologies increasedStriga seed bank over time. Most compound fi elds are thereforedepleted of their natural fertility due to continuous cropping andlow fertilizer application. The acute shortage of land as a result ofincreased population and the presence of undulating hills in thehumid savannas may exacerbate land use intensifi cation. Manyong etal. (1996) reported that land use intensifi cation is driven more by theincreasing population than by market opportunities. Smith and Weber(1994) cautioned that soil fertility would be a serious problem in areaswhere land use intensifi cation was on the increase due to population