That's all true, but deserts can be farmed very profitably if the water is available. Israel is one of the world leaders, they have huge areas of desert growing stuff like Jojoba. If you have a water supply that isn't going to run out, you can build up a soil over the years, growing crops initially that are suited to more sparse conditions. Some crops, like Clover, fix nitrogen from the air in their roots, and improve the soil as they grow.
There's loads of stuff on youtube about growing crops on desert soils.
Edit : More directly relevant to the OP, this youtube video shows Israelis extracting dew from the air, using plastic around the roots of each plant. It starts at 3:10