Crop Rotation Changes in Iowa Due to Ethanol Production

Iowa is the largest corn acreage state with 14.2 million acres which is an increase of 1.6 million acres from 2006. Two sources of data were used for this study. First, NASS calculates the number of acres planted each year for each county. This data is useful to determine general trends; however it will not show where the crops were planted within a county. Secondly, National Agricultural Statistics Service (NASS) has created a land cover classification image each year from either Landsat TM or Advanced Wide Field Sensor (AWiFS) imagery from 2001 through 2007. These images show the location of where each crop is being planted and when combined with each other can be used to determine crop rotations. By analyzing the NASS state acreage reports from 2001-2007, it does not appear that new areas are being put into cultivation. The total area used in corn and soybean production has remained the same throughout this time period. Thus increases in corn acreages have come from decreases in soybean acreages. Based on the NASS land cover classification, the area for the state in a continuous corn rotation has increased from 15.2% in 2001-2002 to 20.9% in 2006-2007. Areas in continuous soybean rotation have diminished from 8.1% in 2001-2002 to 4.3% in 2006-2007. There are thirty three counties which have consistently high accuracies for the 2001-2007 time period. These counties also show that the increase in corn acreages have come from soybean acreages, not from increasing overall agricultural areas.