Yes, we risk turning that wasteland into a desert! /s Considering the crop's nature, we probably have to assume that it won't be used sand for maintaining rice

Yes, we risk turning that wasteland into a desert! /s Considering the crop's nature, we probably have to assume that it won't be used sand for maintaining rice puddles but rather clay or something which can hold water. For higher concentrations of salt partial desalination can be employed. AFAIK, it's only expensive to desalinate if you want drinking water levels, otherwise it's just some filtering. Also, we can expect continuous work on those varieties of salty water rice to eventually be able to support lower and lower desalination maintenance.