Résumé
Rice cropping in lowland conditions in tropical zones frequently encounters the problem of iron toxicity. This edaphic type of constraint is very often observed in West African lowlands and is a nutritional disorder associated with high concentration of iron in its ferrous form in soil solution. This ferrous iron is absorbed in abundance by the rice plant, accumulates in the leaves, creates discoloration of the lamina, reduces tillering and plant height and causes significant yield loss. This constraint was studied in the form of an investigation conducted in three West African countries (Guinea, Côte d'Ivoire and Ghana) with the goal of quantifying the impact of the constraint on rice production in the zones surveyed. The investigation was conducted on over 4600 plots in 757 lowland areas. Over 50% of the lowlands and about 60% of the plots cropped with rice were toxic, and 10% of these lowlands had been abandoned because of excessive iron toxicity pressure. The results also showed that over 55% of the rice area was affected by the constraint. The impact on yield is also significant since the affected plots can lose up to 54% on average of their production potential compared to toxicity-free plots. (Résumé d'auteur)