TRANSITION STRATEGIES FOR POST-CRP CERTIFIED ORGANIC GRAIN PRODUCTION

Authors: DELATE, KATHLEEN - IOWA STATE UNIVERSITY; Cambardella, Cynthia; Karlen, Douglas

Submitted to: Crop Management at www.cropmanagement.org
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2002
Publication Date: 8/15/2002
Citation: DELATE, K., CAMBARDELLA, C.A., KARLEN, D.L. TRANSITION STRATEGIES FOR POST-CRP CERTIFIED ORGANIC GRAIN PRODUCTION. CROP MANAGEMENT at www.cropmanagement.org. 2002. Available from: www.cropmanagement.org.

Interpretive Summary: Organic farming is expanding in the U.S. at a rate of approximately 20% per year. Farmers are interested in organic production because certified organic crops can provide up to a 300% economic premium over conventionally raised crops. However, in order to obtain organic certification, producers must refrain from using synthetic fertilizers and herbicides for at least 3 years. Land that has been in long-term pasture or enrolled in the Conservation Reserve Program (CRP) is often suitable for immediate conversion to organic production because chemicals have not been applied for many years. This study was conducted to determine the efficacy of four commonly-used tillage practices for converting long-term pastureland to organic production. We evaluated crop, weed and insect parameters in soybean, corn and oat planted into bromegrass/alfalfa hay pasture. Spring tillage resulted in slightly higher crop yields presumably due to the timely release of plant nutrients from soil organic matter that had accumulated under the bromegrass/alfalfa pasture. Few differences were observed in grain protein, stand establishment, and insect and weed control for the four tillage treatments. Land managers can successfully use any of the four tillage practices to convert CRP and other long-term pasture ground to organic grain production.

Technical Abstract: Land that has been in long-term pasture or enrolled in the Conservation Reserve Program (CRP) is often suitable for immediate conversion to organic production because chemicals have not been applied for many years. However, conversion of CRP or long-term pastureland to certified organic production will require tillage because the use of herbicides is prohibited. We evaluated stand establishment, weed competition, yield and grain quality for soybean [Glycine max (L.) Merr.] in 1999 and 2000 and corn (Zea mays L.) and oat (Avena sativa L.) in 2000. These crops were planted into a mixed bromegrass/alfalfa sod in south-central Iowa. Primary tillage treatments were fall moldboard plowing, fall tillage with a Kverneland plow, fall and spring tillage with a Howard Rotavator, and spring moldboard plowing. Primary tillage did not affect soybean yield 1999, but in 2000, soybean yields were significantly greater with spring moldboard plowing. Corn yield was greater for both the fall and spring moldboard plow treatments than for the fall/spring rotary tillage treatment. In 2000, the Rotavator treatment significantly reduced soybean stand establishment, possibly because of surface crusting. There were some significant treatment differences in grass and broadleaf weed populations for both years, but overall weed control was considered sufficient. Insect pressure from corn borer (Ostrinia nubialis) and bean leaf beetle (Ceraotoma trifurcata) was below economic threshold levels. Crop yields exceeded the county average each year, suggesting that weed and insect pest competition were negligible. Few differences due to tillage were observed in measured agroecosystem parameters and we conclude that organic grain crops can be successfully produced following CRP or other long-term hay/pasture crops in south-central Iowa.