For many years the IRS battled with taxpayers regarding whether Conservation Reserve Program (CRP) payments received by retired taxpayers were subject to self-employment taxes. The taxpayers argued that once a farmer is retired, the payments are simply rent payments and not subject to these taxes.
The IRS countered that the payments are still subject to SE tax in many cases. This argument went on for many years with various court cases deciding the issue one way or the other.
Congress finally decided to stop part of the argument by passing a law a couple of years ago that stated if a farmer is collecting social security payments, then all CRP payments are exempt from self-employment tax. This is true even if the farmer is still actively farming. This law is in effect for any payments received after December 31, 2007.
When you prepare your form SE to show your income subject to self-employment taxes, you will back out these payments in arriving at your net SE earnings.
The argument is still alive regarding receiving CRP after a farmer retires and before they start collecting social security benefits.