I would get the farmer's input, but this isn't ONEOKs first time crossing good farmland. They pretty much know what they have paid to other farmers.
I had a family member that negotiated the amount they wanted for crossing their land with the pipeline representative.
Then the pipeline representative had to negotiate with the farmer who was leasing the land on the alfalfa crop damage and the re-seeding/fertilizer re-drilling & labor costs.
(Alfalfa Bales Per Acre X Price Per Bale X # Acres X # Cuttings Lost) + (estimated re-seeding/fertilizer re-drilling & labor costs) = Potential Damage Payment to the Farmer
Impacted acreage can be determined by: [length x width] / 43,560 but the ONEOK rep knows this.