The entire cotton trade ran on credit. The cotton factor house advanced money to the planter on the basis of an expected crop. That crop was the collateral. The factor sold the cotton to a broker in New York or a foreign buyer (the actual logistics of this gets complicated, as explained in Five Cotton States). At some point a foreign import/export house might ship a given value of manufactured goods on the promise of an equivalent value of cotton. No money changed hands.
Cotton was particularly suited for credit because unlike corn, sugar, or molasses the goods didn't go bad.