It seems 2/3 - 1/3 varies depending on how risky the ground typically is. The more risk, the more the landowner pays.  We've rented some ground for over 40 years that is 2/3 - 1/3, we pay all crop expenses but lime.   One advantage for us is we don't have to track the expenses.

Talking with a farmer 30 miles south he said he would only rent 2/3 - 1/3 with landowner paying 1/3 of expenses.

Mike,  Bottom line it's whatever the landowner and renter can agree on