MRTN, yes. But MRTP? and MRTK?

Univ. of IL fertility specialist Dr. Andrew Margenot found soil samples from your great-grandfather's IL farm fields. Focusing on phosphorus, and its supply in the soil and its rate of uptake by crops, he and others are developing formulas for "Maximum return to phosphate" and eventually to potash. And he's offering an incentive to farmers participating in the project.