Ammonia used as agricultural nutrient held by farmers and the general duty clause

Does the exemption at 40 CFR 68.125 for "ammonia used as an agricultural nutrient, when held by farmers" apply to the CAA Section 112(r)(1) general duty clause?

No. The exemption for ammonia held by farmers for use as fertilizer applies only to the provisions of the risk management program regulations at 40 CFR Part 68. The general duty requirement is statutory rather than regulatory and is, therefore, not subject to the regulatory exemption at 40 CFR 68.125.