Improved Management of Iron-Affected Soils for Casamance Rice Production.

Casamance is a region in southern Senegal that traditionally produces rainfed rice, which is a primary cereal for human consumption. However, the Senegalese population consumes more than 900,000 tons of rice per year and the total national production is around 300,000 tons per year. In addition to record rainfall deficits in recent years, soils in the region have a variety of physical and chemical characteristics that stress rice plants and reduce the amount of lowland field that can be cultivated. One of those stresses is iron toxicity, which is prevalent in lowland areas that produce the majority of rice and results from the acid sulfate soil type this is common in the region. The objective of this work is to investigate the use of soil amendments to improve soil fertility, mitigate iron-toxicity, and increase rice yield in Casamance lowlands. Experimental field plots were established during the 2014 growing season to test the following soil treatments: agricultural lime, pulverized oyster shell, biochar, and control (no amendment). A variety of chemical and biological characteristics were analyzed at four different times during the growing season including transplantation, panicle initiation, flowering, and harvesting. Plant tissue samples and agronomic data were also collected to quantify improved fertility and rice productivity. Preliminary results show increased soil pH and decreased total iron in experimental plots amended with lime and shell. Yield parameters are also significantly higher in plots amended with shell. Results of this work contribute to a better understanding of iron cycling among multiple components of the Casamance lowland ecosystem and will hopefully help recover currently unproductive lands that are necessary to meet food demands of the Senegalese population.

Keywords: Iron toxicity, amendments, acid sulfate soil, Casamance