The Environmental Benefits Index is an index that has been used by the FSA Farm Service Agency of the United States Department of Agriculture since 1990 to rank farmers’ requests to enroll land into the Conservation Reserve Program during each general sign-up period. The only enrollment mechanisms that do not use the index are the Conservation Reserve Enhancement Program and continuous enrollment, for which a total of 4 million acres (16,000 km2) has been reserved. The index continues to be adjusted from general signup to general signup.