About a ton an acre for Virginia tobacco, but I took soil science 30 years ago, so my memory is not that great.

And, I made an error, as food-grade is not the right term because that means something else. What I meant was, the kinds of phosphate fertilizer used in tobacco production are (hopefully) not used for food or feed production. Within the US, the source is, IIRC, apatite from the south-eastern US. Other countries have other sources.

General discussion of the American context (US EPA): http://www.epa.gov/radiation/sources...rial_cigarette Note the end note. Nobody really knows what is in US-market cigars.

... and Doc, the normal curve is bell_shaped, not brick-shaped. What is applicable to the population does not apply with certainty to any individual. Somebody wins the lottery, it doesn't mean that everyone will win the lottery. Some people taste chocolate in cigars; it doesn't mean you will. ;-)