Take care of tires on Storage

I actually have my 2720 SL sitting on my backyard this day's and is sitting on the top of my grass ,my question ,besides tires covers (which i have ) is any other thing i should do to improve the life of my tires such as live them on top of wood instead of the grass , etc ???,i appreciated any idea or suggestion . Thank you

Ps I also leave my trailer sitting on the scissor jack stands,to take some the weight of the tires .