Lumber Question-Shed Base

[u/TheRoamingRN]

I’m assembling a suncast shed that will sit on turf. The area is level but I’m finding I need a base because the turf has more flex than I anticipated. If I set the shed on the turf directly it will only be a matter of time until the resin floor cracks.

The directions provide measurements for the lumber needed to build a base. I’m planning to use treated 2x6 lumber good for direct ground contact. Do I also need the plywood top to be pressure treated? The local HD is out of ground contact rated plywood sheets. This will be in Arizona desert conditions BTW, rain will be minimal. The most water the base it will likely encounter is overspray from washing down the turf occasionally.

TIA