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Bello, L.L.; Ojo, A.A.; Adeyemo, M.O. & Omojor, Y.M. Résumé Une etude sur le terrain a ete menee pendant deux saisons de croissance dans la savane Guineenne au Nigeria, pour evaluer l'effet de planter tot sur trois cultures de soja (Glycine max (L.) merrill). On a plante dans une periode de deux semaines en avance, et deux et quatre semaines plustard apres la periode recommandee pour planter. La date x d'interaction pour planter emit considerable pour la production de semence et les composants de semence. Il y a eu de differences considerables en moyenne de production de semence avec retard de planter apres les dates recommandees pendant les deux annees. Les gousses par plante et les branches par plante, pendant la periode de planter tot, ont plus pousse en comparaison avec celles durant les periodes recommandees. Cependant, ii y avait une reduction dans ces parametres par rapport a la periode de planter tot. I1 n' y avait pas de differences significatives dans la viabilite de semence apres huit a dix mois de stockage de cultures. Ainsi, le flexibilite de planter certaines grains de soja avant la periode recommandee dans la savance au sud de la Guinee est faisable sans effet detrimental sur la qualite et la quantite de produit de semence. Mots Clés Glycine max, la performance du rendement

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Effects of planting date on yield components and seed viability in soybean in Southern Guinea Savanna, Nigeria Bello, L.L.; Ojo, A.A.; Adeyemo, M.O. & Omojor, Y.M. Abstract A field study was conducted during two growing seasons in the Southern Guinea Savanna of Nigeria, to assess the effect of early and late plantings on three soybean (Glycine max (L.) Merrill) cultivars. Planting was done two weeks before, at, and two and four weeks after the recommended planting time. Seed yield and yield components (pods per plant and branches per plant) were measured. Planting date x cultivar interaction was significant for seed yield and yield components. There were significant differences in average seed yield among planting dates and a progressive decline in average seed yield with delay in planting after the recommended date in both years. Pods per plant and branches per plant, in early planting, were more than or comparable with those planted within the recommended periods. However, there was reduction in these parameters with late plantings. There were no significant differences in seed viability after eight to ten months of ambient storage of the cultivars. Thus, flexibility of planting certain soybean cultivars earlier than the recommended planting period in the Southern Guinea Savanna is feasible without detrimental effect on quality and quantity of the seeds produced. Keywords Glycine max, yield performance

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