February 13, 2012

Herbicides were developed during the 20th century to be used with conventional tillage for weed control. Conservation (or minimum) tillage subsequently evolved, which enabled less soil damage when used with herbicides. Selection pressure, however, has resulted in weed species that have made adaptations for survival in conjunction with tillage. A new issue paper from CAST (the Council for Agricultural Science and Technology), Herbicide-resistant Weeds Threaten Soil Conservation Gains: Finding a Balance for Soil and Farm Sustainability, examines the impact of certain weed management practices on soil conservation objectives and addresses ways to mitigate negative effects.

One of the paper’s authors is Dr. Robert Wilson, weed specialist at the UNL Panhandle Research and Extension Center at Scottsbluff. Wilson notes that the western Nebraska is among the areas experiencing the problem of herbicide-resistant weeds. He said glyphosate-resistant kochia has been found in the Ogallala area. The U.S. government has put several federal policies and programs in place that help determine the selection and implementation of crops and conservation programs in relation to herbicides and tillage. The authors of this paper discuss those programs with regard to:

• The disagreement among organizations, there being no simple solutions.
• The need for collaboration among all parties.
• A case study of Palmer amaranth, “one of the most high-profile problems,” in Georgia cotton.

The balance between conservation tillage and herbicide-resistant (HR) weed management is the central issue addressed in the paper. As the
authors state, “The fundamental conflict facing many producers with HR weed management issues today is the choice between using tillage or land
stewardship practices that protect soil and water resources.”

Among the paper's conclusions are

• Soil conservation is threatened by HR weeds.
• Growers are including and/or intensifying tillage practices because of HR weeds.
• Education programs are needed to show HR weed management without losing recent gains.
• More research is necessary regarding HR weed management and soil conservation goals.

Task force authors include UNL’s Wilson; David Shaw, Chair, Mississippi State University; Stanley Culpepper, University of Georgia; and Micheal Owen,
Iowa State University; and Andrew Price, National Soil Dynamics Laboratory. The full text of CAST Issue Paper 49 is available online at the CAST website, www.cast-science.org, along with many of CAST’s other scientific publications. All CAST Issue Papers and Commentaries are free. CAST is an international consortium of scientific and professional societies, companies, and nonprofit organizations. It assembles, interprets, and communicates credible science-based information regionally, nationally, and internationally to legislators, regulators, policymakers, the media, the private sector, and
the public.

Contacts for this paper are:

Dr. David Shaw—Phone: 662-325-3570; E-mail: dshaw@research.msstate.edu
Dr. John M. Bonner—Phone: 515-292-2125, ext. 225; E-mail: jbonner@cast-science.org

News Release
UNL Panhandle REC, Scottsbluff