I'm not sure the dirt itself is that important, in that soil is made up of peat, loam, compost, clay, sand in varying amounts. It's probably easy to find some soil somewhere here in the US that is almost exactly the same type of soil as in the Nic tobacco fields, or so close that adding something to it would make it so. Also, the amounts of fertilizers and water added to soils make a huge difference in growing things.
Temperatures (between night & day, max & mins, duration through the year) probably have something to do with it, but from what I have learned tobacco can be and is successfully grown over a wide range of geographical area.
It is my opinion that by far the biggest piece of the puzzle to quality cigar tobacco production is when to pick the leaves, hanging them in a temperature and humidity-controlled environment until they're completely brown, fermenting them such that they are heated in a controlled manner at a very closely monitored within a narrow range of temperature and humidity for a certain amount of time, and then packed and stored in a temperature and humidity controlled manner for a much longer time. And knowing when they're "done." And then, blending the right amount of ligero leaf with seco and volado, and rolling and wrapping it all into a cigar that will draw right.
All of that above stuff isw highly labor intensive. The cheaper the labor, the less the ultimate cost of the cigar. After growing, picking, drying, fermenting and curing a small quantity of leaf myself, I am convinced that it's not so much the dirt, it's the WORK. I am further convinced that if premium cigars were made in the U.S., they'd be just as good as any other premium cigar from anywhere else, but they'd cost $350 each, simply because of the labor costs.
Just my $.02. Here's a link to a previous post here on the subject.
[ame="http://www.botl.org/community/forums/showthread.php?t=32770"]Anybody else grow Havana leaf? - BOTL Cigar Forums - Brothers of the Leaf[/ame]
