I am an expert and I think this is a really bad idea. I mean the idea is alright, but you might find you have some problems in execution.
@downtide: Four years will not turn whites into vinegar if stored properly. Many white wine varieties have excellent long term ageing potential. There are Rieslings and Sauternes that really come into their own at 50–70 years. Most “drink while young” white wines turn to vinegar due to the introduction of acetobacter, which converts the ethanol to acetic acid. So assuming the winemaker has taken the necessary precautions to avoid acetobacter contamination, white wines can age. Whether or not they improve is another matter…but I digress.
Ok. Let’s say that I was just absolutely set on doing this and I wanted it to be successful.
I would definitely consult with experts in my area to find out how deep I would need to go to maintain a constant temperature of 55–65 degrees Farenheit. Temperatures above 78 degrees Farenheit for even one or two days can “cook” the wine, spoiling its intended flavours. Humidity is also a factor. The wine needs to stay humid enough to not dry out the cork, but not so humid as to allow the growth of mildew. (Some molds can actually be beneficial, but once again, I digress…)
Next, I’d want to be sure I had chosen a wine that did have the potential to get better over the next four years. There are lots of wines that fit this category, so it’s really about preference.
The hand of the winemaker in the post fermentation/ bottling stage is another consideration. The last half of the 20th century saw vast improvements in cleanliness and hygeneic production of wines. Stainless steel fermentation vessels, sterile bottling procedures and copious use of sulfur dioxide led to wines that are considerably more shelf stable than wines from even 40 years ago. Wines became subjected to better forms of filtration to remove not only errant particles, but also bacteria and micro organisms which could produce “off flavours” such as brettanomyses, acetobacter which could start a vinegar conversion, or even wild yeasts which could start a secondary fermentation in the bottle (which is how one Dom discovered sparkling wines. But I digress…) So I would choose a wine that was fined and filtered as well as one that was not free of added sulfur dioxide, two things that are very “off trend” for today’s natural and organic driven wine market.
Lastly I would store the bottle on its side in some other form of airtight container.
I might choose a wine with a screwcap closure to avoid any cork spoilage. Yes, there are wines meant for ageing that are bottled in screwcap.
But really, all of this is what wine cellars were designed to do. You wouldn’t chop down a tree with a fork, when a saw is available, would you?
I get the idea of the romance of burying the bottle and then digging it up and sharing it. How about a nice bottle of Maker’s Mark Bourbon. Impervious to heat and cold (well, those extremes anyway) and comes provided with a nice wax seal. Dig a shallow hole. Throw it in. See ya in 2016!
Good luck!