Question

why did southern farmers oppose Hamiltons plans for econemy

Answer 1

Alexander Hamilton was a brilliant, far-sighted economic planner. His plan for economic development and growth included a plan called "assumption'; the federal government would assume the war debts from the individual states. Some southern states were opposed to it, like Virginia and Maryland, because they had already levied high taxes to pay off their war debts. Now they would be taxed to pay the debts of other states as well, especially those of the northern states.
Source:
http://www.tax.org/Museum/1777-1815.htm
"Alexander Hamilton" - Ron Chernow
"Alexander Hamilton" - Richard Brookhiser
"American Nation" - Carnes, Garrity
"A Leap in the Dark" - John Ferling

Answer 2

They didn't want to pay taxes to help the northern states, where many had already almost finished their share of war debt.

Answer 3

Alexander Hamilton was a brilliant economic planner. His plans for economic development included a plan called assumption; the federal government would collect that the war debts from individual states. Sothern states opposed his idea, like Virgina and Maryland because they already had a high increase in taxes. They didn't want to have to pay other state taxes as well as their own.