I've read accounts of the potatoes-in-a-barrel plan over the decades. My impression is that the thoughtful, data oriented people who believe that it produces greater yield never say that it produces a barrel full of potatoes or that potatoes grow from the stem.
They just say that if they
(1) use longer season varieties and
(2) keep adding covering material (soil, straw, whatever) in small amounts at frequent intervals so that the growing stem never becomes green until it has reached the desired height and is allowed to emerge
they get larger yields, which they sometimes attribute to a small but significant elongation of the stolon producing region.
My first recollection of this concept didn't involve barrels, but pens -- sort of like the "potato towers" some use, but not as elegant -- and the goal was to get a good yield with minimal space and easy harvest of clean potatoes. The potatoes were planted at the bottom of the pen, then frequently layered with straw, and sides were dropped to harvest by just raking out the straw.
I've done variations of this -- all of which worked OK. I've never had results as good as some credible people reported -- but I've never grown the longer season potatoes which it is suggested, reasonably, I think, work best for this method.
Two possibly useful thoughts about the pen/barrel/tower approach, though:
1) It might make it possible to grow potatoes in climates not ideally suited to them, by making it possible to put the pen/barrel/tower in a compact location that was cooler, drier, or whatever was needed to make potatoes happy. So those in hot climates might not need to be deprived of new potatoes, for example.
2) An often reported necessary element is to prevent the stem from turning green until it has grown to the desired emergence point. The few remaining potatoes from our last year's crop, stored in a completely dark cool closet, have looooooooong white sprouts -- long enough that they could be planted and covered a couple of feet deep with their still-white sprouts just emerging or near the point of emergence.
I doubt that I'll have time to prepare a place for any of these, then creep out in the dusk to plant them without letting the stems have any incentive to green up . . . and none of them are long-season potatoes . . . but for anyone planning to try a barrel experiment, it might be interesting to use seed potatoes that had been kept in the dark until they developed very long sprouts , to minimize the difficulty of the "keep adding straw (or whatever) to cover them enough to keep the stem from greening up until they grow to the desired emergence point."
'Tis a thought, anyway.
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