Subsurface Drainage of Valley Bottom Irrigated Rice Schemes in Tropical Savannah (Case Studies of Tiefora and Moussodougou in Burkina Faso)

The impact of subsurface drainage on ferrous iron concentrations in the African Tropical Savannah rice irrigated valley bottom soils was investigated. The investigations and the analyses where implemented both in two typical valleys (Tiefora and Moussodougou) and in designed experiments. The results showed that subsurface drainage increases ferrous iron concentration in the hematite dominant soils - from 935 mg/l to more than 1106 mg/l in the case of the soil of Moussodougou – but also reduces soil acidity – from pH 5.6 to 7.3 in Moussodougou. This effect will eventually reduce ferrous iron intake by rice roots, alleviating toxicity.