The Long-Term Agroecological Research (LTAR) Experiment Supports Organic Yields, Soil Quality, and Economic Performance in Iowa

The Long-Term Agroecological Research (LTAR) experiment, at the Iowa State University (ISU) Neely-Kinyon Farm in Greenfield, IA, was established in 1998 to compare the agronomic, ecological, and economic performance of certified organic cropping systems to conventional counterparts. Cropping systems were designed based on local farmer input and practices. In the second LTAR phase (2002 to 2010), equivalent organic and conventional corn (Zea mays) and soybean (Glycine max) yields were achieved in the organic corn-soybean-oat (Avena sativa)/alfalfa (Medicago sativa) (C-S-O/A) and corn-soybean-oat/alfalfa-alfalfa (C-S-O/A-A) rotations compared to the conventional corn-soybean rotation (C-S). Organic oat and alfalfa yields, at 103 bu/acre and 4.4 tons/acre, respectively, exceeded county averages of 73 bu/acre and 3.3. tons/acre, for the same period. Similar plant protection occurred in organic crops, without the use of petrochemicals, compared to conventional crops maintained with synthetic pesticides. In Fall 2009, soil organic carbon, total nitrogen, and extractable K and Ca were 5.7%, 9.5%, 14.2%, and 10.8% higher in organic soils, respectively. Soil properties related to biologically active organic matter were up to 40% higher in organic soils. Economic returns to land and management in 2010 were $510/acre in the organic C-S-O/A-A rotation compared to $351/acre in the C-S rotation. The LTAR experiment will be continued as a valuable demonstration of the potential for organic crops to achieve comparable yields while increasing carbon sequestration and economic returns compared to conventional corn and soybean rotations.