Iron toxicity is one the major edaphic constraints of lowlands in West Africa. All types of lowlands, with or without water control, can be affected by this constraint that occurs when significant quantities of iron are present. The reductive conditions commonly found in clogged lowland soils are signs of iron toxicity through the solubilization in the soil of virtually all the iron content in its ferrous form (Fe2+). This large amount of ferric ion solution causes imbalance in the elements resulting in nutritional disorders affecting crop growth, especially in rice. Work conducted by WARDA aimed on the one hand to develop improved, tolerant and productive lowland rice lines and, on the other hand, to design cropping systems to mitigate the effects of the constraint. The eco-regional dimension can be approached through integrated interdisciplinary research on this theme conducted at WARDA. It is therefore possible to develop the first diagnostic tool for iron toxicity risk in the lowlands by employing a dichotomous key based on pedology, hydrology, agronomy, and eco-physiology.