Wetenschap - 1 januari 1970

Soil salinity in Sahel misunderstood

Soil salinity in Sahel misunderstood

Soil salinity in Sahel misunderstood


The increasing salinity of the soils in the Sahel has long been
acknowledged as a catastrophe for agriculture in the region. The cause of
the problem is often attributed to the relatively new irrigation systems,
which are believed to increase the amount of salt reaching the soil. Recent
PhD graduate Piet van Asten concluded from his research that this is not
the case. Salt accumulation has more to do with the underlying bedrock, and
a shortage of nutrients in the soil is a bigger problem.

Van Asten examined soils in the irrigated areas of Foum Gleita in
Mauritania and the Sourou Valley in Burkina Faso. He found that most soils
in these two areas did not fall under the classification of salty soils
according to international standards. He also showed that the geographical
distribution of salt was not related to the presence of irrigation or
drainage canals. He did find alkaline salts in the upper soil layers in
Foum Gleita, but soil and ground-water samples showed that the salts did
not come from irrigation water, but from the deeper-lying bedrock.

The idea that the big irrigation projects in the Sahel, which were started
after the serious droughts of the seventies and eighties, are responsible
for problems of salinity arose at the beginning of the nineties when annual
yields declined drastically in many areas. “At that time the first signs of
the formation of alkaline soils were observed in the area with the oldest
large-scale irrigation scheme in the Sahel,

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