Submitted to: ASA-CSSA-SSSA Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 7, 2003
Publication Date: November 7, 2003
Citation: DELATE, K., CAMBARDELLA, C.A., CHASE, C., DUFFY, M., FREIDRICH, H., BURCHAM, B., HARTZLER, R., DEWITT, J. COMPARISION OF ORGANIC AND CONVENTIONAL CROPS IN A LONG-TERM AGROECOLOGICAL RESEARCH (LTAR) SITE: YIELDS, SOIL QUALITY AND ECONOMICS IN YEARS 1-6. ASA-CSSA-SSSA PROCEEDINGS. 2003. CD-ROM. MADISON, WI.
In our long-term comparison of replicated conventional and organic systems, organic corn (Zea mays L.) yield was 91.8% of conventional and organic soybean [Glycine max (L.) Merr.] yield was 99.6% of conventional yield over 3 years of the transition to organic production and 1 year of certified organic production at the Neely-Kinyon Long-Term Agroecological Research (LTAR) site in Greenfield, Iowa. Total organic carbon (TOC) concentration in the top 15 cm of soil increased by 9% over 4 years in the 3- and 4-year organic rotations that contained forage legumes and were amended with composted swine manure compared to minimum TOC changes in the conventionally managed corn-soybean rotation. The extended organic rotations accumulated an average yearly total N input of 114 kg N ha-1 despite the relatively high tillage intensity. Grass and broadleaf weed populations varied between the organic and conventional systems each year, but the impact on yield was considered negligible. Corn borer and bean leaf beetle populations were similar between systems, with no effect on yield. Returns for corn and soybean within the organic rotations were significantly greater than conventional corn-soybean rotation returns. The first 5 years of production will be compared to other organic research sites across the U.S. to elucidate differences in yield and economic returns among sites.