Bob, it might just be something as easy as the deep soil holds more moisture, and the shallow soil might be more rocky or something and doesn't hold as much moisture or hold on to as much fertilizer.

All I know is the tomatoes I grow in expensive potting soil, with expensive fertilizer and sprays and care - act like little primadonnas.
The ones that come up from seed in the yard act like weeds!

Corrie

This is always interesting. Many people when trying to nail down what makes a certain location or particular patch of dirt "good" are very keen to look at nutrient content and water retention. Both are very important factors, but don't really paint the whole picture. This is especially so when it comes to comparative performance with one group doing perceptibly better, but for seemingly imperceptible reasons. The soil in with the "meadow" tomatoes may be lighter and spongeyer. I can now speak with experience when I say that oxygen levels at the root zone makes a HUGE difference in tomato growth. (see our thread Innovative indoor tomato grow for a comparison between oxygen-boosted and normal plants) Also, your meadow location most likely sees much more natural decomposition and thus a much more active microbial population. The naturally occurring(or artificially induced in our case) ecosystem that lives in any good soil seems to lend towards cases of plants that have a touchy-feely sense of being "better" while being difficult to actually measure. More vigor, stouter, better tasting; individual qualities that are hard to find a real reason for in the perceived big picture are often the responsibility of pro-biotic or mycorrhizae (usually both) life webs. Old world "tonics" added to a planting bed involving beer or vinegar or what have you that showed results for no apparent reason usually worked because they fed the local micro-life, not because they provided some essential nutrient to the plants that otherwise would be missed. Some tonics provided food, some would modify the soil chemistry so as to be more preferable to a particularly beneficial aerobacteria and still others would wipe out competing microbes while leaving the preferable ones alive. The only problem being that nobody had any idea what was actually going on. Even now soil science is just beginning to embrace the real impact that microlife can have on plants. In fact it is now being hypothesized that mycorrhizae fungus, which science has known to have evolved long before plants for some time now, was essential for the evolution of terrestrial plant life. Without complicated chemical testing it would be tough to say if this is indeed the advantage that your meadow patch has. I would suggest that, this coming season, you pick up some of Espoma's Bio Tone Starter Plus which is a mild organic fertilizer that contains a variety of mycorrhizae spores and dormant beneficial bacteria. Add this to your shallow soil, leave it out of your meadow soil and see if the plants closer to the house wind up looking more similar to the meadow plants. Given what you've told us, its what I'd bet on as being the main difference. Good luck and happy gardening!
-Zach

Here is a link that might be useful: our tomato diary