Vadose zone

The vadose zone is the damp portion of earth above the waterline (saturated zone) and below the surface. On land, water in the vadose zone has a pressure head less than atmospheric pressure and is retained by a combination of adhesion and capillary action. On some large natural floating islands, the vadose zone extends well below the water line: in other words, where you’d expect to find saturated soil, there is a dry zone, even below the water-line. What this means for floating island technology is that – potentially – all kinds of terrestrial plants could grow in this zone, even on salt water.