ACP was a cost-sharing program, the farmer paying part of the cost of "approved conservation practices", ASCS paying the other part. It was early in the Nixon administration, which didn't believe in the program (thinking it basically enhanced production so should be entirely paid for by the farmer). They ended up in a battle with Congress over the program, resulting in a number of changes. Over the years it was reformed again and finally moved to SCS (which had always fought with ASCS over it).
Why do I babble on about it? This bit from Farm Policy:
"In other policy related news, Mark Peters reported in today’s Wall Street Journal that, “Kevin Hollinger planted radishes and oats last fall in his corn and soybean fields, but he isn’t planning to harvest them. Instead, he is letting the crops die over the winter to improve the soil and keep fertilizer and other nutrients from running into nearby waterways.Winter cover were one set of the conservation practices covered by ACP. I find my memory is foggy here. I don't know whether they were dropped, like lime was, and later reinstated into EQIP and CSP or whether they have always survived.
“‘I could hardly go to town without someone asking: ‘What’s that in your field?’’ said Mr. Hollinger, a fourth-generation farmer.
“Helping to foot the bill for his experiment is a pilot program set to launch fully next month. Farmers in the Ohio River basin are being paid to make changes—from what they plant to how they handle manure—in an effort to minimize runoff that can cause hypoxia, or low oxygen levels, in waterways.”