This is a good take on the Challenge. Could be a touch crisper, and maybe that righthand upper corner could have been used to add something extra to the image. It's pretty neutral now. All in all, a good photo.
Not a good composition I'm afraid. Those shapes don't lead the eye anywhere, and the blown out sky attracts the eye by sheer force of its whiteness. It's difficult to say exactly where you think the main centre of interest is here, as there appears to be no one thing as a primary subject. The light is far too general to capture good texture.
Until you touch one! ;) Those cacti can be real nasty because the needles are extremely difficult to get out. Good DOF, though I would like to see a bit more clarity in the front. I really enjoy the colors though. Really, I can't wait until summer when there will be nice blue skies to work with again. Good luck!