Influence of Cover Crop Rotation and Conventional Practices on Grapevine Plant Growth and Weed Growth
Dennis Portz, graduate student & Gail Nonnecke, professor, Department of Horticulture
Cover crops are used in rotation with cropping systems to improve soil quality and to suppress pests. Use of cover crops prior to replanting on sites with grape may provide a sustainable alternative to chemical pesticides and may maintain or improve soil quality. The objectives of this study were to investigate how cover crops affect weed and nematode populations and soil physical and chemical properties when used on replant sites with Vitis spp. (grape).

Weed Management and Soil Quality in Vineyard Agroecosystems
Craig Dilley (PhD candidate) and Dr. Gail Nonnecke, Department of Horticulture, ISU. Cooperators: Dr. Bruce Bordelon, Purdue University, Dr.Harlene Hatterman-Valenti, North Dakota State University
A project to examine the effects of conventional and alternative weed management systems on soil quality in vineyards in three states was initiated in 2004. Weed management treatments include: 1) conventional herbicide, 2) cultivation/tillage, 3) straw mulch, and 4) a living mulch of creeping red fescue ( Festuca rubra ). The goal of the project is to identify optimal weed management practices for soil quality and grapevine growth and development. A sub-objective of the project is to determine biological parameters that can be measured and used in combination with standard chemical and physical soil measurements to indicate an improving or declining condition of a vineyard soil. Data from the measurements will be normalized and incorporated into a mathematical index, called a soil quality index, to be used to gauge the level of an improving or declining soil condition.

2002 Leopold Center Grape Cultivar by Management System Trial

Through a grant from the Leopold Center of Sustainable Agriculture, a grape cultivar by management system trial was established in 2002 at the ISU Horticulture Research Station (Hort Station), and at the ISU Armstrong Research and Demonstration Farm (Armstrong Farm). The trial was designed to evaluate 15 cultivars under three management systems. In 2002, 10 wine cultivars [Maréchal Foch (Foch), Frontenac, Cynthiana (Norton), St.Croix, Chambourcin, Seyval Blanc (Seyval), La Crosse, Vignole, Traminette, Edelweiss], and four seedless table cultivars (Marquis, Vanessa, Reliance, Mars) were planted at the two locations, with the seedless cultivar Jupiter to be added in 2003. The three management systems being evaluated are a conventional system that relies on herbicides for weed control, and the application of insecticides and fungicides on a regular basis; an IPM/best management system that uses herbicides as needed, and relies on monitoring to determine the need for insecticides and fungicides; and an organic-approved system, that relies on alternative methods of weed control and the use of organic-approve insect and disease control strategies.

The vines were planted in mid-May. At each site, the vines were spaced 8 x 10 ft apart (545 vines per acre) with three vines per replication. Treatments were replicated five times at the Hort Station, and three times at the Armstrong Farm. Vines training will be to the bi-lateral cordon system on a 2-wire trellis with wires at 3.5 and 6.0 feet, and post spaced 24 feet apart. Vines with a procumbent (trailing) growth habit will be trained to the top wire, while those with a semi-upright to upright growth habit (Chambourcin, La Crosse, Seyval, Traminettee, Vignole) will be trained to the mid-level wire with catch wires added above.

2003 Wine Grape Cultivar Trial

Through an Iowa Department of Agriculture and Land Stewardship (IDALS) specialty crops grant awarded to the Iowa Grape Growers Association (IGGA), a wine grape cultivar trial was established in 2003 to evaluate the adaptability, productivity, and wine making quality 20 new cultivars and advanced selections at four locations in Iowa: ISU Horticulture Research Station, Ames; ISU Armstrong R & D Farm, Lewis; ISU Southeast R & D Farm, Crawfordsville; and ISU Northeast R & D Farm, Nashua. These sites represent three different climatic and four different soil conditions.
The vines were spaced 8 x 10 ft apart (545 vines per acre) with three vines per replication. The Crawfordsville and Nashua plantings included the cultivars being evaluated in the 2002 Leopold Center grape cultivar by management system trial. Treatments are replicated four times at each site (12 vines per cultivar). Vines training will be to the bi-lateral cordon system on a 2-wire trellis with wires at 3.5 and 6.0 feet, and post spaced 24 feet apart. Vines with a procumbent (trailing) growth habit will be trained to the top wire, while those with a semi-upright to upright growth habit will be trained to the mid-level wire with catch wires added above.

Cynthiana Grape Cultivar Propagation Study

‘Cynthiana’ (Norton) has shown promise as a wine grape for adapted regions of Southern Iowa, but unlike most grape cultivars, it is difficult to propagate from cuttings. Studies have found that rooting can be improved by treating the cuttings with rooting hormone such as indole-3 butyric acid (IBA). The use of bottom heat to simulate root development before bud breaks has also been shown to be beneficial. A student special studies project was established to evaluate the effect of bottom heat in combination with rooting hormone treatments on the rooting of ‘Cynthiana’ grape cuttings.

Horticultural and Chemical Practices Influencing Fruit Quality with ‘Reliance’ and ‘Swenson Red’ Grape Cultivars

Fresh table grapes can be grown successfully in the Midwest, and can add a new opportunity for agricultural diversification and local food systems. However, to be competitive, local growers will need to product high quality grapes to compete with out of state supplies. Practices that improved berry size, cluster appearance, or advance fruit maturation would increase the marketability of locally grown grapes. Gibberellic acid (GA3) has been shown to improve berry size in seedless cultivars and loosen clusters of seeded cultivars when applied at specific times. Practices that regulate crop load, such as cluster thinning and removing a portion of the cluster (tail thinning) have been shown to advance maturity of both seeded and seedless grapes. Tail thinning has also been shown to improve cluster appearance in some cultivars. This study was undertaken to evaluate these various practice to improve quality and advance maturity of seeded and seedless table grapes under Iowa growing conditions.

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