Well, what I was trying to say, simply put, is that if the soil isn't contaminated, then you can take your half-drum, cut off the bottom/top, lay it on the ground (maybe dig a few inches for greater stability), and then fill with soil/substrate. It's almost the same as above ground planting, except that the direct contact between your drum's substrate and the ground means:
- generally better drainage of excess water
- better protection from drought via capillarity (ground humidity will wick into the drum)
- allows the plants to grow some taproots reaching further down for better drought resistance
And if you ever need to move it, as long as it's not frequent, you can just tilt the barrel, cut everything growing between it and the soil, and roll it to the new spot. Less practical to move than a pot with a bottom, but hops are never really practical to move during growing season anyways due to their need for trellis.