Leopold Center for Sustainable Agriculture

Leopold Center project looks at weed control in vineyards

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August 5, 2009

AMES, Iowa -- Not only do Iowa vineyards produce great wine, but in the future, Iowa-grown grapes may be among the most sustainably grown in the country. The question is: how can Iowa grape growers reduce their chemical use and control weeds while still producing high yields and high-quality fruit? Iowa State University horticulture professor Gail Nonnecke is researching sustainable solutions to this problem.

The latest grape-growing project, funded by the Leopold Center for Sustainable Agriculture and led by Nonnecke, looks at weed control alternatives to herbicides and pesticides in Iowa vineyards.

“The grape industry is growing and is an important part of Iowa’s agriculture. To produce excellent grapes, controlling weeds while keeping yields high is vital,” said Nonnecke, commenting on the importance of the project.

The research compares four weed control methods: herbicides, cultivation, mulch and living mulch.

The conventional herbicide and cultivation treatments leave the ground bare, exposing soil to erosion. Lisa Wasko, graduate student in horticulture and soil science who is working on this project under Nonnecke, said, “Whenever you have bare soil, it is more susceptible to the elements and compromises the productive capacity and the physical, chemical and biological attributes of the soil.”

Nonnecke and Wasko agreed that the cultivation method also seems to decrease yield more than the other methods of weed control.

Straw mulch is effective and often used by organic vineyards. The straw controls the weeds, but also retains more moisture than other methods. According to Wasko, grape vines grow best when they have do not have constant wet roots.

For the living mulch treatment, Nonnecke planted creeping red fescue (Festuca rubra), which prevents weeds from appearing and grows around grape vines to serve as a ground cover. Creeping red fescue is dense, which blocks the weeds and preserves the biological attributes of the soil.

“We need a weed management system that maintains soil quality, provides excellent growth and development and provides high fruit quality. If we can have this practice and provide it to Iowa grape growers, that would be an excellent addition,” said Nonnecke. “By using practices that enhance soil quality of the vineyard, we can increase the sustainability of the vineyard in the long-term.”

Watch a video about Nonnecke’s project on the Leopold Center Web site here.

LEOPOLD CENTER RESEARCH SETS STAGE FOR ADVANCES IN IOWA WINE, GRAPE INDUSTRIES

In addition to supporting current research on alternative weed management for Iowa vineyards, the Leopold Center for Sustainable Agriculture has made numerous investments in the future success of the state’s grape and wine industries.

The Leopold Center’s research support was instrumental in establishment of the first American Viticulture Region (or AVA) in Iowa that was recently approved by federal regulators.

The new region, the Upper Mississippi River Valley AVA, includes 18 counties in northeast Iowa and is the largest in the United States. A two-year Leopold Center grant helped Limestone Bluffs RC&D in Maquoketa start the application process in 2005. The result was the valued AVA designation that recognizes unique grape-growing regions and opens new markets for quality Iowa wine.

In 2002, a Leopold Center grant supported establishment of vineyards at the Iowa State University Horticulture Research Station near Ames and the ISU Armstrong Research and Demonstration Farm near Lewis. The research compared 15 cultivars under three types of management: conventional production with regular applications of herbicides and pesticides; an IPM/best management system that relies on monitoring to determine the need for chemical insect and disease control; and an organic-approved system.

The Leopold Center also has provided seed money for the Midwest Grape and Wine Industry Institute at Iowa State University in 2006. In 2000, the Center issued a widely-cited “Grape Expectations” report about historical grape production and potential for redevelopment of the industry in Iowa.

More information about AVA wine regions and a summary of the Leopold Center-funded project are here.

An overview of Iowa State University grape research appears at: viticulture.hort.iastate.edu/research/research.html.

For more info contact:

Gail Nonnecke, ISU Horticulture, (515) 294-0037, nonnecke@iastate.edu

Jeri Neal, Leopold Center Ecology Initiative, (515) 294-5610, wink@iastate.edu

Allison Severson, Leopold Center communications intern, (515) 294-5272, ajs86@iastate.edu

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