ARS | Publication request: The long-term agroecological research (LTAR) experiment supports organic yields, soil quality, and economic performance

Submitted to: Crop Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2012
Publication Date: N/A

Interpretive Summary: Organic management is an attractive alternative to conventional cultivation methods for producers interested in gaining premium prices for their crops while lowering input costs. This study evaluates organic and conventional corn- and soybean-based cropping systems at the Neely-Kinyon Long-Term Agroecological Research (LTAR) site near Greenfield, IA to identify grain production practices that sustain yields, maintain economic viability, and enhance soil quality in the first decade after transition to certified organic production. Grain yield was equal and soil quality was higher in the organic compared to the conventional rotations. At the end of the first decade of organic management, economic returns to land and management were greater for the four-year organic rotation. Our study shows growing organic grain crops within expanded legume-containing crop rotations can result in economically-viable crop yields and enhanced soil quality during the first decade after transition to certified organic production. This information will be useful to scientists seeking to understand the effects of organic management on agroecosystems, and to farmers who are contemplating transitioning to organic production.

Technical Abstract: The Long-Term Agroecological Research (LTAR) experiment, at the Iowa State University Neely-Kinyon Farm in Greenfield, Iowa, was established in 1998 to compare the agronomic, ecological and economic performance of conventional and organic cropping systems. The main goals of the project are to evaluate cropping system alternatives to the conventional corn–soybean rotation in Iowa. The certified organic systems are designed to substitute local, renewable input sources in contrast to inputs based on off-farm energy, and to increase the internal resilience of agroecosystems, which consequently increases their adaptability to potential climate changes. We report here results from the second phase of the LTAR site (2002 to 2010) comparing these rotation treatments: 1) C–S: conventional corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]; 2) C–S–O/A: organic corn-soybean-oat (Avena sativa L.)/alfalfa (Medicago sativa L.); and 3) C–S–O/A–A: organic corn-soybean-oats/alfalfa-alfalfa. Conventional crops were maintained through synthetic fertilization and pesticides, while organic–compliant amendments and pest management methods were utilized in organic plots. Successful outcomes from the second phase of the LTAR experiment included equivalent organic and conventional corn and soybean yields; similar plant protection without the use of petrochemicals; and higher soil quality in organic fields. 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. Organic corn and soybean yields over 9 years in the C-S-O/A-A rotation averaged 178 bu/acre and 51 bu/acre, respectively, compared to 180 bu/acre and 49 bu/acre in the conventional C–S rotation. These results have encouraged the transition to more ecologically-diverse methods of farming in Iowa.