The parasitic angiosperms, Striga hermonthica and S. gesnerioides, obligate root parasites endemic in sub-Saharan Africa, constitute severe constraints to cereal and legume production in West and Central Africa. Over the years, a range of effective component technologies has been identified for Striga control in Africa. The potential of these technologies has been demonstrated under researcher-managed conditions. To promote farmer testing of the technologies, community workshops were conducted in 42 rural communities in Kaduna State, northern Nigeria. These revealed that agriculture was the main source of livelihood for most households. The three most important crops, maize, sorghum and pearl millet are attacked by S. hermonthica, regarded as the major constraint to crop production, often causing 70–100% crop loss. Farmers recognised two types of Striga damage (underground and aboveground), with greater damage being caused by underground Striga. Farmers attributed increasing incidence and severity of Striga damage to lack of capital, poor soil fertility, infestation of previously uninfested land by Striga seeds, and continuous cropping of host crops. The most widely used among the 15 existing Striga control techniques identified by the farmers were hoe weeding and hand pulling, application of inorganic fertilizer and manure, crop rotations, fallowing, and early planting. In assessing possible control measures farmers considered increased crop yield, reduced Striga reproduction and Striga emergence, greater crop vigour, and increased soil fertility as positive attributes. Negative attributes comprised increased labour requirement, higher costs, increased risk of crop damage or yield reduction, and lower quantity and quality of produce. Overall, a legume-cereal rotation was the most highly rated control option for S. hermonthica management evaluated by the farmers. The implications of these results are examined with respect to farmers' adoption and adaptation of Striga control options beyond the experimental plots.

Maize improvement at the International Institute of Tropical Agriculture (IITA), which began in the 1970s, built on the germplasm and experience of earlier years. The main breeding emphasis was to develop maize cultivars and hybrids with high yield potential and durable resistance to diseases and pests with specific adaptation to the different agro-ecological zones of West and Central Africa. Over the years, open-pollinated cultivars have been developed with different levels of resistance to biotic and abiotic stresses. Identification of the factors that contributed to improvements in the maize cultivars developed during the past decades may be useful to sustain the genetic gain from selection in the future. A study was conducted to quantify genetic gains in yield and associated traits of open pollinated maize cultivars released from 1970 to 1999 in the West African savannas. The genetic gain in grain yield was 0·41% per year and seems to be associated with increases in total biomass and kernel weight, and reductions in plant height and days to flowering (anthesis and silking). There was no significant change in harvest index of the cultivars.

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The Guinea savannas of Nigeria have a high potential for the production of maize because of favourable environmental conditions. Despite this high potential, the yields obtained in farmers' fields are still very low. This is due to soil degradation and nutrient depletion arising from intensification of land use. Nitrogen (N) is the major nutrient limiting maize production in the Guinea savannas where the use of inorganic fertilizers is low. One strategy for improving the productivity of maize is to select varieties that perform well under suboptimal soil N conditions. This study assessed the performance of diverse maize germplasm under a range of N levels. Growth and grain yields differed significantly between the genotypes at all N levels. These variations were more pronounced at zero and 30 kg N ha −1 than at 90 kg N ha −1 . Grain yield under N-deficient conditions was correlated with an increased number of ears per plant, stay-green rating, leaf chlorophyll concentration, leaf area index, reduced anthesis-silking interval and reduced days to silking suggesting that these traits are linked to tolerance to N deficiency. One hybrid (Oba Super 2), the drought-tolerant genotypes and four maize genotypes previously selected for tolerance to N-deficient conditions performed better than the widely grown adapted controls under zero and 30 kg N ha −1 . At zero N, the grain yield of maize decreased with advances in cycles of selection for tolerance to suboptimal N conditions suggesting that N deficiency in the selection environment was not sufficient to discriminate between genotypes. The good performance of drought-tolerant varieties under suboptimal N conditions suggests that selection for drought tolerance may confer tolerance to N-deficient conditions.

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