Correcting the pH of soil

1Polders are scattered around Lake Chad which, one day, could feed a large part of the region’s population. These polders are the ongoing results of old research conducted by researchers. While the soil surrounding Lake Chad is very fertile, it is also particularly difficult to cultivate, due to its high clay content. Water does not seep in easily. It stagnates and deposits mineral salts which make the land alkaline and less permeable. If precautions are not followed, this soil can quickly become infertile. Researchers solved this problem from 1950 to 1980 by adding gypsum and limestone to soil in order to change its pH, promote water drainage and boost yields.

Salty soil, Thailand.

••• By improving certain agricultural techniques, scientists converted land unsuitable for agriculture into arable land •••

2In the 1970s, in West Africa this time, similar research was conducted on mangrove ecosystems with a view to making soil exposed to brackish water suitable for agriculture. The mangrove salinisation issue was even more complex, as salt was not the only challenge to be tackled to reclaim these milieus. Once it has been dried, mangrove land tends to oxygenate and to become acidic enough to kill plants. Scientist however found solutions on a case-by-case basis, by building small dams, using parcel lifting or pH modification techniques. In the 1980s-1990s, this experience led to a more experimental phase, followed by the modelling of soil acidification and salinisation phenomena. It became possible to provide farmers with suitable cultivation techniques prior to planting or sowing.

Mangrove rice field, Guinea.

“Orstom’s work served as a basis for stimulating research on the reclamation of salty and acidic rice-growing land in the mangroves and tannes of the Basse Casamance region, an issue which has become even more critical in light of climate change, the fight against desertification, biodiversity conservation and the decrease in agricultural and crop production in West Africa. Research currently conducted by the Assane Seck University of Ziguinchor is driven by the desire to build and update scientific knowledge while developing certain ecosystem services related to the mangrove, such as solar salt, a recent ground-breaking initiative which is currently under review.” 
Lamine Fall, teacher-researcher, Assane Seck University of Ziguinchor, Senegal