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Legume-maize rotation and maize nitrogen (N)-response trials were carried out simultaneously from 1998 to 2004 in two distinct agro-ecological environments of West Africa: the humid derived savannah (Ibadan) and the drier northern Guinea savannah (Zaria). In the N-response trial, maize was grown annually receiving urea N at 0, 30, 60, 90 and 120 kg N ha -1. In Ibadan, maize production increased with N fertilization, but mean annual grain yield declined over the course of the trial. In Zaria, no response to N treatments was observed initially, and an increase in the phosphorus (P) and sulphur (S) fertilizer application rate was required to increase yield across treatments and obtain a response to N applications, stressing the importance of non-N fertilizers in the savannah. In the rotation trial, a 2-year natural fallowmaize rotation was compared with maize rotated with different legume types: green manure, forage, dualpurpose, and grain legumes. The cultivation of some legume types resulted in a greater annual maize production relative to the fallow-maize combination and corresponding treatments in the N-response trial, while there was no gain in maize yield with other legume types. Large differences in the residual effects from legumes and fallow were also observed between sites, indicting a need for site-specific land management recommendations. In Ibadan, cultivation of maize after the forage legume (Stylosanthes guianensis) achieved the highest yield. The natural fallow-maize rotation had improved soil characteristics (Bray-I P, exchangeable potassium, calcium and magnesium) at the end of the trial relative to legume-maize rotations, and natural fallow resulted in higher maize yields than the green manure legume (Pueraria phaseoloides). In Zaria, maize following dual-purpose soybean achieved the highest mean yield. At both sites, variation in aboveground N and P dynamics of the legume and fallow vegetation could only partly explain the different residual effects on maize.

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Two sets of on-farm trials, each covering two years, were conducted in the northern Guinea savannah of Nigeria over the period 1999-2001, the objective being to compare integrated Striga hermonthica control measures (soybean or cowpea trap crops followed by maize resistant to Striga) with farmers' traditional cereal-based cropping systems. In both sets of trials, this proved to be highly effective in increasing productivity over the two year period, especially where soybean was used as a trap crop. Resistant maize after a trap crop increased the net benefit over the two cropping seasons in both trials by over 100 % over farmer practice. However, in the second set of trials there was no significant increase in productivity between a trap crop followed by Striga resistant maize, and a trap crop followed by local maize especially where legume intercropping and fertilizer had been applied in the farmer practice. There was also no increase in productivity between two years' traditional cereal cropping and one year's local maize followed by Striga resistant maize. This indicates the importance of a legume trap crop in the first year in order to ensure high productivity in the second year, regardless of variety. Up to 20 % of farmers obtained higher productivity from their own practices, notably intercropping of cereals with legumes and use of inorganic fertilizers. Leguminous trap crops and Striga resistant maize, together with two key management practices (increased soybean planting density and hand-roguing) were seen to be spreading both within and beyond the research villages, indicating that farmers see the economic benefits of controlling Striga. Survey findings show that explaining the reasons why control practices work can greatly increase the adoption of these practices. Wider adoption of Striga control will therefore require an extension approach that provides this training as well as encouraging farmers to experiment and adapt Striga control options for their local farming systems. I N T RO D U C T I O NStriga hermonthica, a parasitic flowering plant, endemic to Africa, constitutes one of the most severe constraints to cereal production in sub-Saharan Africa. It parasitizes sorghum, maize, millet, rice and sugar cane, as well as pasture and wild grasses, by attaching itself to the roots of the host plant diverting essential nutrients and leaving the host stunted and yielding little or no grain, often causing yield losses in excess of § §