This study was built to investigate the impact of subsurface drainage on iron toxicity in Tropical Savannah irrigated rice valley bottoms. The research leaned upon two complementary approaches: field investigations and designed experiments. Important results, covering several fields, where achieved. For example, It appeared that single-season irrigation schemes present higher iron toxicity and acidity risks than double-season ones – 750 up to 1800 mg/l of Fe2+ higher in the single-season scheme of Moussodougou than in the double-season scheme of Tiefora. Furthermore, a statistical analysis of flow time series (ARIMA model) data was performed. It showed that with a simple water level measurement probe installed at the main gate of the scheme, it becomes possible not only to quantify irrigation water consumption, but also to diagnose farmers' irrigation schedule, providing them a means to defuse potential conflicts due to inequity in water distribution. Finally, it was shown that subsurface drainage increases ferrous iron concentration in hematite dominant soils soil – from 935 mg/l to more than 1106 mg/l in the case of the soil of Moussodougou - but also fortunately alleviate soil acidity – from pH 5.6 to 7.3 in Moussodougou. This effect will eventually reduce ferrous iron intake by rice roots, alleviating toxicity.
Keïta Amadou (Bamako, 1964) followed his primary education in Mali at the Lycée Askia Mohamed. He obtained his engineering degree in Hydraulic Engineering at the National School for Engineers (ENI) in Bamako in 1987. He specialised in Agricultural Engineering at the Ecole Inter-Etats d’Ingénieurs de l’Equipement Rural (EIER, now 2iE) in year 1991. After that, he joined in 1992 the International Water Management Institute (IWMI) that implemented a project on irrigation performance assessment and diagnosis in Burkina Faso and Niger. From 1997 to 2006, Mr. Keïta became the subregional coordinator of the FAO project GCP/RAF/340/JPN, the activities of which were focused on the development and experimentation of sustainable low-cost and water efficient small irrigation systems. The irrigation systems were designed to use simultaneously surface water and shallow groundwater for small scale farming. The actions of this project were implemented in three countries: Burkina Faso, Mali and Niger. The office of the FAO project was located within the International School for Water and Environmental Engineering (2iE) in Ouagadougou, where Mr. Keïta started giving lectures in irrigation and drainage. While being coordinator of the FAO project, Mr. Keita obtained a French Master degree in physics and chemistry at the University of Ouagadougou in Burkina Faso in 2003. In year 2008, Mr. Keïta obtained a Master of Science degree in Land and Water Development at UNESCO-IHE Institute for Water Education in Delft, The Netherlands. Afterwards, he returned to 2iE and continued lecturing in irrigation and drainage. He completed a PhD in Land and Water Development at UNESCO-IHE in 2015. Mr. Keïta’s current research addresses the issue of drainage of cropland for production improvement. Iron toxicity is one of the most important challenges to rice research and production in Africa, and subsurface drainage of waterlogged valley bottom irrigated rice systems is viewed as a viable solution to alleviate iron toxicity in Tropical Savannah valley bottom soils.
