The Sumerians had a salinization problem.
Evaporating water left behind layers of
salt, and rising water tables brought more
salt to the surface.
A solution to the problem was to leave
lands not watered for many seasons, to let
the water table fall and let rain wash the
salt down far below the surface.
But this would have taken years. It was not
done.
Wheat is less tolerant of salt than barley,
and Sumerian clay tablets describe the
Sumerian diet changing from wheat to
barley. Then the growing of barley and
other crops diminished and the
Sumerians suffered from hunger,
malnutrition and disease. A Sumer
weakened has been described as unable
to defend itself