The Southern production is established by the official records. Yes, the South did produce 72+ % of the total trade value with Europe in 1860.
I cite Thomas Prentice Kettell, but the official records reflect the same numbers. They have been posted in previous threads on this topic.
Sadly, DiogenesLamp's "72+%" is a lie, only potentially true if by "the South" you mean every state "South" of New York, and if by "total trade value with Europe" you delete the values of California gold and Nevada silver exported to balance-up our trade deficits.
But by more honest accounting, Confederate states' cotton in 1860 made up ~50% of total US exports, no more.
Other products like tobacco would add ~7%, but they were mainly grown in Union states & regions -- i.e., Kentucky, Maryland & Pennsylvania, not in the Confederacy.
And even the legitimate $200 million in Confederate state cotton exports of 1860 are exaggerated in saying they "paid for" 50% of Federal tariff revenues.
We know this because in 1861, when Confederate cotton was deleted from US exports, Federal tariff revenues fell only ~15%, not 50%, much less 72%.
So DiogenesLamp's 72% number is pure Democrat Confederate propaganda, of no value in explaining anything, but still used by propagandists from that time to ours.