DR. Don Research Update
Reviewing organic cultivars, minimizing weed seed banks and the downfalls of growing corn conventionally

By Don Lotter

February 24, 2004: The American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, held their annual meetings in Denver, Colorado this year and used an Organic Agriculture Symposium to feature their latest findings in organic research, in this week’s Research Update Don Lotter reviews the highlights of these meetings.

Identifying cultivars specific tailored to organic needs will result in superior performance

Other presentations at the Symposium included...
• Maintaining Agroecosystem Health;
• Organic Farming Research in the Pacific Northwest;
• State of the Organic Union: the USDA/ARS Organic Agriculture Research Portfolio;
• Research Approaches in Organic Agriculture: How Best to Study Organic Production Systems?;
• An Update of Organic Research and Outreach at the University of Minnesota's Southwest Research and Outreach Center;
• Sustainable Agricultural Farming Systems;
• Importance of Understanding Site-Specific Weed and Nutrient Management Strategies in Organic Production Fields;
• Organic Research and Extension in the U.S. Land Grand System: The Ground Swell Builds;
• Long-Term Organic Farming Systems Research at USDA-ARS, Beltsville

North Dakota State researchers led by Patrick Carr showed their research on small grain cultivar selection for organic systems. There has long been a need to develop crop cultivars adapted to organic systems, as currently available cultivars of wheat, barley, and oat were selected for use with synthetic fertilizers, herbicides, and pesticides.

One trait that has been asked for by organic farmers is early shading, in which leaves rapidly grow out from the plant instead of straight up, as many of the modern nitrogen tolerant, high yielding cultivars do. This is for shading out of weeds, organic crop managers’ biggest problem.

It has also been thought that cultivars that pre-date modern agricultural inputs – fertilizers, herbicides, and pesticides -- should do better in organic farming systems.

The North Dakota researchers’ objectives were to: 1) identify wheat, oat, and barley cultivars that are adapted to organic management; 2) determine if old cultivars are better adapted than modern ones to organic environments; 3) determine if crop lines adapt to the organic environment over generations; and 4) identify crop traits for organic environments.

Their conclusions were: 1) small grain cultivars and traits do indeed exist that make for superior performance in organic systems; 2) modern varieties nevertheless outperformed old varieties; 3) crop lines do indeed show adaptation when grown organically over generations; and 4) the researchers were as yet unable to identify crop traits identified with superior performance under organic conditions. Lead researcher email: Patrick.Carr@ndsu.nodak.edu

Reducing weed seed production reduces the weed seed bank

USDA researchers looked at weed seed bank dynamics as affected by rotation diversity and conventional vs. organic management. The more diverse rotation, corn-soy-wheat-hay, had significantly less seed survival than the corn-soy rotation. Both were organic. When the researchers looked at weed seed survival in organic vs. conventionally managed soils, there were no differences, although the results were complicated by a severe drought.

The researchers did find that, even with seeds that have a long seed bank life, there was a survival rate of only about 50% the first year and 30% the second year. They conclude that weed seed banks can effectively be reduced within a few years by reducing weed seed production.
Lead researcher email: ullrichs@ba.ars.usda.gov

Conventional comparison: Corn, more Nitrogen, more root disease

A multidisciplinary team led by researchers from the Michael Fields Agricultural Institute presented a wide-ranging and exciting study of soil and root dynamics on organic and conventional farms in the Midwest. “Organic Corn Production, Organic Matter Management, and Root Health” was a data-rich presentation and had some interesting conclusions:

  • Despite inputs of synthetic nitrogen fertilizers, corn took most of its N from soil organic matter. Fertilization with synthetic N increased corn N uptake by only about 11%.
  • For each ton of grain yield, conventional corn took up 28% more nitrogen from the soil than organically grown corn.
  • Retention of carbon in soil is four times higher for carbon from compost than carbon from corn stover.
  • Conventionally grown corn had nearly twice as much root disease as organic corn. This is basically the same result as I found in my research on organic and conventional vineyards in California 1997-1999 (conventional vines had three times more root disease than organic).
  • Conventional corn had root:grain ratios of 65:1 while organic corn averaged 38:1. It is the increased disease that causes the corn plant to produce more roots, and this is why the N uptake is less efficient in conventional corn.
    Lead researcher e-mail: wgoldstein@michaelfieldsaginst.org

All of these presentations can be accessed at the Minnesota Institute for Sustainable Agriculture website at www.misa.umn.edu.

Don Lotter has a Ph.D. in agroecology and has worked in sustainable agricultural development in North America, Latin America, and Africa over the past 25 years. He can be contacted via his website www.donlotter.com

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