By decreasing their standard of living.
I may be wrong, but I believe that by definition a subsistence farmer, which much of the country was in 1860, is pretty well insulated from the market. Especially in the cash poor South. There would a small investment in the simple farm equipment of the day, but he's not going to buy many manufactured goods, especially from the North. They grew their own food, produced their own clothing, but had no stake one way or the other over the economic issues that concerned the cash crop producers. I've seen a copy of my North Georgia great great great grandfathers' will of 1859 and there's not much there that wasn't produced locally.
He was no doubt consuming a large percentage of those hundreds of millions of dollars in imports 4CJ says were bought by the South.