Cover Crops as a Floor Management Strategy for Pacific Northwest Vineyards

Cover Crops as a Floor Management Strategy for Pacific Northwest Vineyards

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Mercy Olmstead, Viticulture Extension Specialist, WSU Prosser IAREC
Cover crops are an important vineyard floor management strategy. Topics covered include the benefits of using cover crops versus other floor management strategies, as well as information on many different types and species of cover crops and the advantages and disadvantages of each. Guidance is provided on what to consider when choosing a cover crop for a particular vineyard, with instructions on seed-bed preparation and cultivation. Tables summarize planting and cultivation data in both English and metric units. Contact information is provided for several companies selling cover crop seed. The publication is illustrated with color photographs.
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Introduction: Vineyard Floor Management

Vineyard managers should consider the entire ecosystem as the context for the sustainable production of quality grapes. Vineyard floor management can have a large impact on  the abiotic (e.g., temperature, wind, and precipitation) and biotic (e.g., beneficial insects, pests, and disease) factors in a vineyard, especially microclimate modifications and soil health. Decisions about what floor management system to use should take overall vineyard management into account.

Types of Floor Management Systems

Resident vegetation. Resident vegetation consists of all plant species growing within the vineyard. These include both native plants and invasive weeds. The diversity of native plants varies by region of viticulture production. A major advantage of this system is the lack of planting costs; however, invasive weed species may be difficult to eradicate once established.

Management of resident vegetation usually requires mowing to reduce plant height to accommodate vineyard traffic. Mowing frequency is determined by the type of plant species present. In vineyards not certified organic, the area under the vine may be kept weed-free with an herbicide application in the spring. Resident vegetation management is an economical alternative, as the primary expense is limited to the cost of mowing.

Figure 1. Sloping vineyards with clean cultivated alley rows can be particularly vulnerable to soil erosion.
Clean cultivation. In conventionally managed systems, vineyard alleys are disked or sprayed with herbicides to reduce vegetation, while in organically farmed systems, mechanical means or approved organic products are used to keep vineyard alleys weed free. While this method reduces competition with the grapevine for water and nutrients, the exposure of bare soil can increase erosion in prone areas such as slopes (Figure 1). Tillage and equipment travel through clean-cultivated alleys can also contribute to root zone compaction and problems with water infiltration.

Cover cropping. Vineyard cover crops can be managed a number of different ways. Most commonly, crops are seeded in every alley to provide cover throughout the vineyard (Figure 2). They can also be planted in alternate alleys, each with a solid stand of a different cover (e.g., grass and legume), or alternating with alleys that are clean cultivated.  In some vineyards using sustainable management, the area immediately underneath the vine is kept clean with herbicide applications or cultivation to reduce competition for nutrients and water with the vine, especially with drip-irrigated systems. Vineyards using an organic management strategy must utilize mechanical means due to strict regulations on the use of synthetic chemicals for organic certification.

Figure 2. Perennial grass mix in a young vineyard.

Utilizing Cover Crops as a Floor Management Tool

One of the biggest impacts of cover crops is the protection of the soil surface. Wind and water erosion can strip the upper soil layers up to 2.5” in a growing season. Conversely, soil accumulates in areas that contain vegetative cover (Coldwell et al. 1943). Cover crops, especially grasses, protect the soil by



Copyright 2006 Washington State University

Published August, 2006

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