As already mentioned, for lower contrast in a high contrast situation -- deserts in the full sun -- you have basically already under-exposed the film somewhat. That typically means over-developing the film -- which increases the contrast.
In your situation, the solution is easy -- but time-consuming. Take a few tests shots at ISO 50, on a new roll, in a similar situation -- as close as you can get -- and develop them as you might expect (or as others advise). If the results are OK, you are all set. If they are too contrasty, take another set of shots -- only a few are needed -- and adjust the development (change the developer, dilution, time, method, etc.). Rinse and repeat.
Another point to consider, desert scenes normally should have plenty of contrast, and you can always use a lower contrast paper & developer/method.
I'd run some easy tests before you develop any of the film.