The old Locomotive & Railway Preservation magazine had the plans for a "Weed Killer" for tracks. Basically, it was a "wick" system that was mounted on a MOW push cart. It consisted of a couple lengths of PVC pipe, a Tee, a valve, a small tank, a some woven rope and the fittings to put it together. The main PVC pipe had holes in it with three rope loops laced through it. The center loop was track gauge and the outer loops extended to maximum track clearance. The supply valve from tank was opened to supply the main PVC pipe and thus saturate the rope "wicks". It worked as the saturated ropes, drooped just above tie top level, as the unit was pushed along the weeds and grass would be wiped with a dose of good systemic weed killer, e.g. Roundup. In a few days, no more weeds and grass growing in/on tracks. This wicking method worked better than spraying weed killer, that wasted the weed killer and had unintended killing of other plant life (over-spray).