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Title: AGROECOSYSTEM PERFORMANCE DURING TRANSITION TO CERTIFIED ORGANIC GRAIN PRODUCTION

Author
item DELATE, KATHLEEN - IA STATE UNIVERSITY
item Cambardella, Cynthia

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2004
Publication Date: 9/1/2004
Citation: Delate, K., Cambardella, C.A. 2004. Agroecosystem performance during transition to certified organic grain production. Agronomy Journal. 96:1288-1298.

Interpretive Summary: During transition from conventional to organic management practices, farmers frequently document reduced yields for several years prior to long-term recovery in crop productivity. The objectives of this study were to identify grain production practices that sustain yields, grain quality, and soil fertility during the transition period to organic production. The study was conducted at the Neely-Kinyon Long-Term Agroecological Research (LTAR) site near Greenfield, IA. We evaluated crop, soil, weed, and insect pest parameters in conventional and organic rotations during transition to certified organic production. Crop yield and grain quality in the organic rotations were equal to or greater than in the conventional corn-soybean rotation for all years. Small differences in soil fertility, weed and insect pest populations did not translate to yield differences among the systems. Our study shows growing organic grain crops within expanded legume-containing crop rotations can result in economically-viable crop yields during the three years of 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 transitiong to organic production.

Technical Abstract: Implementation of the 2002 U. S. Farm Bill will create incentives for transition from conventional to certified organic production. Our objectives were to identify production practices that sustain yields, grain quality, and soil fertility during the transition period. We compared replicated conventional and organic systems, using identical corn (Zea mays L.), soybean [Glycine max (L.) Merr.], oat (Avena Sativa L.), and alfalfa (Medicago sativa L.) cultivars in all phases of various crop rotations at the Neely-Kinyon Long-Term Agroecological Research (LTAR) site near Greenfield, IA. Organic corn yield was equivalent to conventional yield in the transition years and significantly greater (8.1 vs 7.1 Mg ha-1) in the fourth year of the longest rotation (corn, soybean, oat/alfalfa, alfalfa). Organic and conventional soybean yields were similar during transition, but in the fourth year, organic soybean yield was significantly greater (3.0 vs 2.7 Mg ha-1). Organic oat and alfalfa yields equaled county averages throughout the 4-yr period. Pre- and post-harvest soil test values in 1998 were responsive to manure application, but showed few significant differences between systems during the first year or after four years (2001). Grass and broadleaf weed populations were significantly different for the two systems each year, but the impact on yield was negligible. Corn borer (Ostrinia numbilalis) and bean leaf beetle (Ceratoma trifurcata) populations were similar between systems, with no effect on yield. Grain quality was also similar between organic and conventional systems. We conclude, that by using expanded crop rotations, organic grain crops can be successfully produced during the three years of transition from conventional to organic production practices.