Ezra Klein had a piece in the Post today, discussing reconciliation and the filibuster. His piece, upon which I commented twice, brought back memories. The Budget Reconciliation Act of 1974 was passed in a time of warfare between Congress and the President, and ASCS, the predecessor agency of FSA, was caught in the middle. President Nixon made much more extensive use of impoundment than prior Presidents. If I recall correctly, he impounded the entire appropriation for the Agricultural Conservation Program, which was about $200 million. Under this program ASCS shared the costs of performing "conservation practices" with farmers (yes, the principle survives in current programs). Fiscal conservatives didn't like it because the practices sometimes (or often, depending on the viewpoint) increased production (like liming fields), which was at cross-purposes with the production adjustment aspects of other ASCS programs. For ASCS the impoundment was particularly serious, because commodity prices were high (Nixon had taken us off the gold standard and made the grain deal with the Russians and oil prices were rising--all of which boosted corn and wheat prices) so the agency wasn't busy. Losing the ACP would probably have meant losing a third or so of the ASCS bureaucrats in the county offices.
It's my memory there was a court challenge to his impoundment authority, which he lost. Impoundment looks very like a line-item veto, which the Supreme Court eventually disallowed.
A separate historical thread was the "imperial Presidency"--in 1974 Congress had found its authority within our government waning. It lacked staff, it was disorganized in spending and budgeting, Nixon was grabbing all the authority he could get. So the 1974 Act was just one piece of the effort to make Congress operate better and redress the power balance between the President and Congress. Of course, Nixon's resignation in August confirmed the swing of the pendulum to Congress.