Amaranth is way, way more tolerant of drought and poor soil than corn. But it won't produce super well under those conditions, so you'll probably want to give it *some* water and quality soil.
It's quite rich in protein, and is close to being a perfectly balanced amino acid source. But - and this is very important - it contains various anti-nutritional substances that means amaranth grain
should not be eaten raw. Lots of food sources are like this, actually, so don't be too concerned. But if given to
chickens as a major part of their diet, the raw grain will eventually kill them. Cooked amaranth is a great animal
feed, if for some reason you don't want to eat it yourself. The leaves of both 'vegetable' and 'grain' varieties are edible and very nutritious, though a bit bland.
The biggest problem I had with it is getting the seeds out of the heads without bringing along countless tiny insects and arachnids.