[1] Variables such as drying costs are yield dependent, so are taken from price to get actual price per bushel received (i.e. - Corn price of $2.74 less drying costs of $0.11 generates $2.64 per bushel actually received by farmer). 

[2] These are variable costs for wheat and soybeans in a double-crop rotation.

[3] Costs were actual costs experienced by cooperating producer.

[4] Strips that meet both economic and NRCS criteria for enrollment.