You don’t need fusion to desal the deserts. There already is a giant thermonuclear reactor in the sky showering the deserts with 330+ days a year of full sun. Commercial panels output 450’watts using exactly 2 sq meters of cell area Th st means in a 10 hour day we will throw out the first and last two hours of daylight at Saharan summer vs winter the yearly full sun avg is 10 hours per day. So 2.25 kwh per square meter per day. It takes 3kWh to desal a cubic meter of seawater to fresh water so each sq meter of surface area makes 0.75 of a cubic meter per day 330 days a year or more.
0.75 cubic meter is 75cm of water over a square meter of surface area. 75cm is 29.5 inches of water per day that’s equal to 29 inches of rain per day per square meter crops in a desert with high ET rates like corn or wheat are going to need 60” per season to grow. That’s two days worth of solar power per square meter flier season you can see that one sq meter of panels would support a hundred sq meters of crops this is the way no fusion needed just cheap panels set at an angle equal to latitude grow crops under the panels the shade will help with the ET loss rates plants don’t need full.blazing desert sunlight it actually too strong for them.
It comes down to cost.
I’ve seen some massive projects around the world that purport to get solar power at the lowest —at around .02 @kwh usually, the numbers on the big solar farms in the desert come in around .035@kwh.
The first-generation fusion plants promise to deliver electricity at .01@kwh.
Where desalination does work currently for farming is with greenhouses because they use water so efficiently. Currently you can see thousands of greenhouses on the coast of southern spain. About ten years ago they put in their first desalination plant to provide fresh water for the greenhouses.
There are smaller operations like this—desalinating sea water for green houses— among gulf arabs and in australia.