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Integrated Weed Management Strategies to Increase Pasture Productivity
J.D. Green, W. Witt, K. Burdine, G. Schwab
Department of Plant and Soil Sciences
Problematic weeds such as tall ironweed, musk thistle, spiny amaranth, buttercup, common cocklebur, and horsenettle have been increasing in pastures during the past several years as grazing has intensified within Kentucky, Tennessee, and the surrounding region where cool-season grasses are the predominant type of forages grown. These weeds are becoming more prominent in pastures because they are unpalatable to animals or have spines or thorns. Livestock producers are seeking ways to increase pasture productivity by minimizing the impact of these weeds on grazed lands. One of the primary methods used to combat weeds in pastures has been mowing, but due to increasing energy cost producers are beginning to question the economic viability of this option. Other weed control methods which are available including integration of weed management practices need to be considered.
The objective of this project is to evaluate mowing (mechanical control), herbicide (chemical control), and added fertility (culture practice) as independent factors and as integrated weed management methods that best reduce populations of unpalatable weed species which compete with the productivity of desirable forage species in grazed pastures. Field research trials will be used to determine pasture productivity relative to these weed management strategies combined with an economic analysis that would assess the cost/benefits of each of these different weed management practices. During the final stages of this project field days will be held, meeting presentations and publications will be used to educate livestock producers, county extension agents, and other interested individuals on best management practices for weed control in pastures.
2010 Project Description
ACTIVITIES: Field studies were initiated in July 2008 at three different sites in Anderson, Madison, and Monroe counties near Lawrenceburg, Richmond, and Tompkinsville, Kentucky, respectively. These on-farm field sites are located on grazed pastures in cooperation with county Extension agents and local livestock producers. Eight different treatments are being studied at each site to evaluate three primary weed management strategies (mowing, herbicide, and added fertility). Treatments range from no strategy (untreated control); mowing alone, herbicide alone, or added fertility; combinations of mowing plus herbicide, mowing plus fertility, herbicide plus fertility; and a combination of all inputs which consist of mowing plus herbicide plus added fertility. Mechanical control treatments were mowed in July 2008 and 2009. Added fertility was applied in September 2008 and 2009 to designated treatments based on soil test results. Herbicide applications were only applied in August 2009. Weed species composition and the density of the primary weeds present (which includes tall ironweed as a common plant species at each site) were determined before treatments were initiated in 2008 and repeated during 2009 and 2010 (one and two years after treatments began). Available forage and weed biomass yields were determined in May 2009, September 2009, and May 2010 by sub-sampling ungrazed and grazed areas within each plot. The amount of forage produced was botanically separated into desirable forage species and weeds present. The economic cost/benefits of each of these treatments are being evaluated based on the cost of weed management inputs and forage yield data.
EVENTS: Three field days for forage and livestock producers have been held at each research location (Madison, August 2009; Monroe, September 2009; and Anderson, June 2010) to highlight the results obtained after the first year of these studies. In-service training sessions for agriculture and natural resource agents, forage agronomists, and others who consult with producers were held at the Madison and Monroe sites in August 2010. Results of these studies have also been presented to livestock producers through the Master Grazer Program and at local and area field days. Presentation have been made at professional meetings such as the North Central Weed Science Society (2009), a joint meeting of the Weed Science Society of American and the Society of Range Management (2010), and the National Association of County Agriculture Agents (2010).
A total of 400 forage and livestock producers attended the field days held at each site. At the two in-service training sessions for agriculture extension agents and other forage agronomists 45 individuals participated. Observed differences in weed populations, weed biomass, and forage yields for each of the weed management treatments were discussed with participants along with the economic assessments for the inputs and forage yields obtained. Participants were given an opportunity to provide their own perceptions of the most practical and sustainable treatments prior to and after field study results were presented.
Tolson, Josh, J. D. Green, and W.W. Witt. 2009. Integrated Management Strategies to Reduce Weed Populations in Pastures. Proc. North Central Weed Science Society, Kansas City, MO. Abstract 64 (79) [CD-Rom] Champaign, IL.
Tolson, Josh, J. D. Green, W.W. Witt, and Greg Schwab. 2010. Integrated Weed Management for Tall Ironweed Control and Improved Pasture Productivity. Proc. Joint Meeting for Society of Range Management and Weed Science Society of America. Abstract 50 (P B-76). Denver, CO.
Lyons, J.K. J. D. Green, B.G. Sears, J. A. Tolson, and T.R. Yankey. 2010 Integrated Weed Management Strategies to Reduce Weed Populations and Improve Grazed Pasture Productivity. Proc. National Association of County Agriculture Agents. Tulsa, OK. July 2010.