IMHO, I would never graze cattle or rent pasture on any agreement but AUD or AUM. This way the stocking rates can increase or decrease according to the amount of grass available. I pay what I consider a fair rate according to the price of beef. This way we can both make a little money on the good years and we both suffer a bit on the years where the price is poor and the grass is poor. We live in shortgrass country, rainfall last year was a spotty 4 inches, Average in my area is 12 inches.  Paid out AUD last year was $1.75 per cow/calf per day. We never have to overgraze to justify a per acre land rent, and we do are not mining the grass until there is nothing left in value for the landlord. If you have to pay for mineral, you would have to figure out those costs per head per day and ad those to your costs as well as your labor costs for looking after them.