Tamp \Tamp\, v. t. [imp. & p. p. {Tamped}; p. pr. & vb. n. {Tamping}.] [Cf. F. tamponner to plug or stop. See {Tampion}.] 1. In blasting, to plug up with clay, earth, dry sand, sod, or other material, as a hole bored in a rock, in order to prevent the force of the explosion from being misdirected.
2. To drive in or down by frequent gentle strokes; as, to tamp earth so as to make a smooth place.
The blast occurred after a machine used by Metro-North workers to tamp down railroad ties apparently cut through a power cable, he said.
I'd fill a test pot to an inch or so of the top with the mix _ without a plant; tamp the mix as usual and fill it with water.