505 ILCS 80/10

Minimum plant food content. No superphosphate containing less than 18% available phosphate nor any mixed fertilizer or custom blend, other than a custom blend consisting in part of unacidulated mineral phosphatic materials, in which the sum of the guarantees for the nitrogen, available phosphate, and soluble potash totals less than 20% shall be distributed in this State. Specialty fertilizers are exempt from minimum plant food requirements for mixed fertilizers and custom blends.