29 C.F.R. § 780.110
"Cultivation and tillage of the soil" includes all the operations necessary to prepare a suitable seedbed, eliminate weed growth, and improve the physical condition of the soil. Thus, grading or leveling land or removing rock or other matter to prepare the ground for a proper seedbed or building terraces on farmland to check soil erosion are included. The application of water, fertilizer, or limestone to farmland is also included. (See in this connection §§ 780.128 et seq. Also see Farmers Reservoir Co. v. McComb,337 U.S. 755 .) Other operations such as the commercial production and distribution of fertilizer are not included within the scope of agriculture. (McComb v. Super-A Fertilizer Works, 165 F. 2d 824; Farmers Reservoir Co. v. McComb,337 U.S. 755 .)
29 C.F.R. §780.110