One specific problem that greatly concerned farmers was the nation's

Money supply is the right answer that one specific problem that greatly concerned farmers were the nation's money supply.

The United States depository expended the supply of money by circulating millions of dollars in paper currency that could not be bartered for silver or gold coins. This speedy growth in goods for trade caused inflation.  And therefore to get this inflation under control the Federal government of the United States discontinued  press-work for greenbacks and then began clearing off its bonds

d.summerains, the last one

it's lower nubia : ) good luck