1 / Agricultural Policy Review The Agricultural Policy Review is primarily an online publication. This printed copy is produced in limited numbers as a convenience only. For more information please visit the Agricultural Policy Review website at: www.card.iastate.edu/ag_policy_review. Ames, Iowa ● Spring 2015 acres in 2006 and 2014, respectively. For row crop acreage, we observe a larger difference between data sources in 2006 than we do in 2014. In 2006, NASS survey data reports 6.3 million more acres than CDL, and NASS reports 2.5 million less acres than CDL in 2014. According to NASS survey data, total corn and soybean acreage increased by roughly ϐive percent from 2006 to 2014, but CDL data shows roughly a 12 percent increase in the same period. While total acreage from both sources seems closer in 2014, the large difference in 2006 is reϐlected in the large percentage change differences from 2006 to 2014. Focusing on land use change from each data source, we calculate  Agricultural Land Use Change in the Corn Belt by Jimena Gonzalez-Ramirez and Yongjie Ji majimena@iastate.edu; yongjiej@iastate.edu T HE CONVERSION of grass-like land to row crops (in our case, corn or soybeans) and general land use change in the Corn Belt region has important water quality implications. Additional agricultural production can increase nutrient runoff into the Upper Mississippi River Basin, thereby increasing the size of the Gulf of Mexico hypoxic zone. We use two data sources from the National Agricultural Statistical Services (NASS) to obtain detailed land use information in the Corn Belt from 2006 to 2014. We also identify and analyze any similarities and discrepancies between both data sources. Focusing on the Corn Belt, we use NASS survey data and Cropland Data Layers (CDL) to obtain corn and soybean acres for twelve states: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota and Wisconsin. The NASS survey website provides county-level data for acres of both corn and soybeans planted from 2006 to 2014, and we convert CDL data to obtain comparable information at the same level. 1,2,3 We utilize ten CDL categories for our land use comparison: corn, soybean, alfalfa, other hay/non alfalfa, switch grass, idle cropland, grass/ pasture land, grassland herbaceous, grass/pasture, and pasture/hay. The corn and soybean categories are used to study changes in row crop acreage, and the remaining eight categories are aggregated into a grass-like category, used to study grass-like land changes. NASS survey does not provide county- level data on planted acres of alfalfa, hay, haylage and pastureland, thus as an alternative source for grass- like land data, we turn our attention to Conservation Reserve Program (CRP) acres. In particular, USDA Farm Service Agency offers CRP enrollment information at a county level. 4 We ϐirst study land use change from 2006 to 2014 by computing total corn and soybean acreage in the Corn Belt. CDL reports roughly 122.2 and 137.5 million combined corn and soybean acres in 2006 and 2014, respectively. NASS survey data reports 128.5 and 135 million combined corn and soybean