Increased salinity of soils is a big issue anywhere where groundwater is used for irrigation and there isn't much rain. Literally hundreds of millions of hectares are affected. [1]

We are probably going to have to attack the problem on many fronts simultaneously. If we could get efficient solar powered desalination, or something based on nano materials, that would be great [2], the current RO process is fairly energy intensive.

But you still have to deal with brine, and that is hard unless you are close to the sea. And if you are close to the sea and in a hot area, I'd personally go with Seawater Greenhouse technology instead. It has many side benefits, albeit probably not suitable for staple crops. [3]

[1] http://en.m.wikipedia.org/wiki/Soil_salinity#Salinity_due_to... [2] http://www.kurzweilai.net/selective-nanopores-in-graphene-dr... [3] http://www.seawatergreenhouse.com

Actually I think breeding salt tolerant plants would be significantly easier than trying to improve desalination. Although we still have the solve the problem of salt build up. But perhaps it will be easier to remove it from soil and plant matter than from water.

In any case the immediate application is to use it places where the soil is already salty. Better desalination wouldn't help there.