Maryland Code, Agriculture § 8-803.8

(a) Except for enforcement as authorized under § 8-803.5(g) of this subtitle, the Department has the exclusive authority to establish standards regulating fertilizer and its application to turf.

(b) A local government entity may not adopt laws, regulations, rules, ordinances, or standards regulating fertilizer and its application to turf.

(c) Subsections (a) and (b) of this section do not exempt a person from complying with any provision of, or any regulation adopted in accordance with, the Environment Article.