  Soil salinization is a major cause of soil degradation and hampers plant
growth. For soils saturated with saline water, the evaporation of water induces
accumulation of salt near the top of the soil. The remaining liquid gets an
increasingly larger density due to the accumulation of salt, giving a
gravitationally unstable situation, where instabilities in the form of fingers
can form. These fingers can hence lead to a net downwards transport of salt. We
here investigate the appearance of these fingers through a linear stability
analysis and through numerical simulations. The linear stability analysis gives
criteria for onset of instabilities for a large range of parameters.
Simulations using a set of parameters give information also about the
development of the fingers after onset. With this knowledge we can predict
whether and when the instabilities occur, and their effect on the salt
concentration development near the top boundary.
