Vineyard Soils

   
Soil characteristics are a critical factor in determining the potential success of a vineyard. Although grapevines can be grown in a wide variety of soil types, the most important characteristics are good internal drainage and adequate depth. High soil pH and sometimes salinity can be of concern in some areas of Texas.

A well-drained soil is often characterized by a subsoil (layer below the topsoil) that is uniformly brown, red, or yellow-orange. Poorly drained soils typically have topsoil or subsoil that is gray or has alternating areas of reddish brown and gray color. The Brownfield soil series in west Texas is a good example of a uniformly reddish-brown soil that is well-drained.

Drainage is important because grapevine roots require oxygen obtained from the pore spaces (air spaces between soil particles) in the soil. Poorly drained soils are easily saturated with water, which fills the pore spaces and excludes air. Such soils can remain saturated for extended time periods. Roots with little or no access to oxygen essentially suffocate; initially they cease to function, but after a short while roots begin to die. Soil drainage characteristics can be evaluated by conducting a percolation test.

Soil depth for vineyards is commonly recommended to be a minimum of 30 to 40 inches before reaching an impermeable layer. Shallow soils limit development of the root system, resulting in smaller vines and greater sensitivity to changes in soil moisture levels. Irrigation must be managed with extreme care on shallow soils, especially under the hot climate conditions of Texas. Deeper soils are much more preferable; grape roots will penetrate very deeply if the soil is permeable. A larger root system can support a bigger vine and is less sensitive to short-term changes in soil moisture.

Internal drainage and restrictive hardpan layers sometimes can be improved through soil management practices prior to planting. Drainage tiles can be installed to improve drainage, but this is expensive and will be most beneficial on somewhat poorly drained soils. Cross-ripping the site to a depth of 4 to 6 feet can disrupt physical barriers such as hardpan or thin rock layer, which can enable grape roots to penetrate to a greater depth. Cross-ripping may require a 6-foot ripping shank and a very powerful tractor.

The water-holding capacity of a soil is also an important characteristic. Soils with a relatively high water-holding capacity can hold much of the rainfall that reaches it, making it available to the grapevines. Higher water-holding capacity also provides a larger buffer for water consumption by the vines. Soils with low water-holding capacity will require very frequent irrigation to maintain adequate soil moisture levels for grapevines. Ideally, a vineyard soil will be deep, well-drained, and have good water-holding capacity.

Information on soil characteristics can be found in the county Soil Surveys prepared by the USDA-Soil Conservation Service; an agency now called the Natural Resources Conservation Service (NRCS). Many Soil Surveys are out-of-print, but copies may be available for reference at the local USDA-NRCS office, libraries, or at the county offices of Texas Cooperative Extension.

The Soil Surveys contain information describing soil types and their properties including average depth, drainage characteristics, and water-holding capacity. Maps of the entire county showing the locations of different soil types are included to assist you in identifying the soils on your site. However, Soil Survey maps are limited in their accuracy and should serve only as a general guide to soil type in your area. The best practice is to get a backhoe and dig exploratory trenches at strategic locations throughout the site.

Grapevines do not require a fertile soil and are actually easier to manage on soils of relatively low fertility. High fertility can lead to luxurious shoot growth that makes canopy management very difficult and can lead to greater problems with cold injury. Soil analysis of both the topsoil and subsoil should be conducted during vineyard site assessment to determine pH and nutrient levels. Salinity should also be analyzed in locations where this might be of concern. Information on soil testing procedures and analysis is available from the sources listed under Additional Resources.

One aspect of soil fertility that is important is soil pH - an indicator of the soil's relative acidity. Nutrient availability to roots is influenced by soil pH and in highly alkaline soils as soil pH nears 8.0, the mineral nutrients iron and zinc become less available. It is generally not feasible to attempt to lower the pH of highly alkaline soils, but iron and zinc for grapevines can be supplemented with the application of foliar fertilizers. Another solution to the problem is to plant vines grafted to a rootstock adapted to high soil pH. The rootstock Fercal has proven to perform well on high pH soils in Texas.

Additional Resources

Soil Testing

Testing Your Soil - How to Collect and Send Samples
Texas A&M University Texas Cooperative Extension

Soil, Water & Forage Testing Laboratory
Texas A&M University Texas Cooperative Extension

Soil Surveys

Soil surveys and related information
Natural Resources Conservation Service

Web Soil Survey
This website from NRCS allows online viewing of soil survey maps and reports for any location in the U.S. This new application greatly enhances access to information on soils.

Texas Online Soil Survey Manuscripts
General and detailed soil maps and complete soil survey manuscripts for selected counties. Additional counties will become available in the future.

Soil Management

Managing Soil Salinity
Texas A&M University Texas Cooperative Extension

Non-Traditional Soil Additives: Can They Improve Crop Production?
Texas A&M University Texas Cooperative Extension

A Practical Guide to the Application of Compost in Vineyards
Pennsylvania State University

Managing Compacted Soils in Vineyards
University of California Cooperative Extension, Tulare County

Soil Quality Institute

Natural Resources Conservation Service

 

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The Texas Winegrape Network was created and is maintained by Edward Hellman. Graphic design by Monika Sobolewska. © Copyright 2007 Texas AgriLife Extension.