CRP is just high grass and scrub brush that doesn't get cut - usually funded by the government to be planted and left untouched for habitat and erosion control. Any large area of high grass could be considered CRP though, funded or not.
Conservation Reserve Program
The Conservation Reserve Program (CRP) is a voluntary program for agricultural landowners. Through CRP, you can receive annual rental payments and cost-share assistance to establish long-term, resource conserving covers on eligible farmland.
The Commodity Credit Corporation (CCC) makes annual rental payments based on the agriculture rental value of the land, and it provides cost-share assistance for up to 50 percent of the participant’s costs in establishing approved conservation practices. Participants enroll in CRP contracts for 10 to 15 years.
The program is administered by the CCC through the Farm Service Agency (FSA), and program support is provided by Natural Resources Conservation Service, Cooperative State Research and Education Extension Service, state forestry agencies, and local Soil and Water Conservation Districts.
Quote from
http://www.fsa.usda.gov/dafp/cepd/crp.htm