Eric Stafne, Mississippi State University
Before planting any vines, the chosen site will need to be prepared by eliminating existing vegetation, deciding which way rows will run, and how far apart to set the vines and rows.
Starting in late summer or early fall of the year prior to planting, kill perennial weeds (i.e., Johnsongrass, bermudagrass, nutsedge, etc.) with postemergence herbicides like glyphosate (Round-Up®). Some sites are suited to low-mowed row middles of native vegetation, while others may require annual planting of winter grasses. Prior to planting, all areas of the proposed vineyard block need to be free of all tree and shrub roots that can sprout. In the fall, deep chiseling down the row will remove roots and break plow pans or clay layers. (Note: All soil types may not benefit from deep plowing. Soils high in clay may simply reseal and eliminate or significantly reduce the benefits of deep plowing.) Follow chiseling with plowing and discing. An ideal vineyard planting site has all vegetation killed and planted to a cover crop, like hybrid sudan, the summer before planting. Follow the summer cover crop with a small grain cover crop the fall prior to planting.
This is also an ideal time to take soil samples to test for nutrient levels and soil chemistry. It can also be an opportunity to examine the soil profile to better understand the soil characteristics below the surface. Take soil samples in the fall, when soil temperatures have cooled down to 50ºF or less. Have a certified soil testing lab prepare a full soil chemistry report. This will help with planning future nutrient adjustments and allow major adjustments to be made before the vineyard is established. Examining the soil profile can also help with understanding soil physical characteristics in the rooting zone (rhizosphere). The issues that can be addressed through this kind of examination are drainage, irrigation and deep pre-tillage.
In regions with low soil pH, take soil samples one to two years prior to planting, either before or immediately after clearing the property. If soils need to be limed, lime should be incorporated prior to establishing a cover crop and worked to a 2- to 3-foot depth at the recommended rate. This is necessary in order to allow the lime to neutralize acid groups in the soil adequately. Another more detailed set of soil samples should be taken prior to planting to make additional pH and fertility adjustments. This is the last time that full incorporation of lime into the potential root zone of the vine will be possible during the life of the vineyard.
If soil samples establish that the site has high residual nitrogen from previous crops, such as potatoes that traditionally are grown with up to 400 lbs N/acre/year, a wheat or other grass cover crop should be grown, harvested, and removed from the site. The soil should be rechecked for residual soil N and the cycle repeated if necessary. Overly vigorous vines are more difficult to manage and may be more susceptible to winter injury and diseases. Therefore, taking the time to prepare the soil properly is not necessarily going to take longer to establish a vineyard and may save money and effort in the long run.
Rows longer than 500 feet are more difficult to manage, and shorter rows ensure uniform drip irrigation water pressure and trellis integrity. Longer rows will likely require braces in the middle of the row to strengthen the trellis. Typical row lengths are between 200 and 300 feet, but it depends greatly on the site. Breaks in vineyard rows can contribute to more efficient vineyard operations, particularly those that are mechanized, such as spraying, or hedging. The value of these features should be weighed against the maximization of vine numbers and total vineyard productive space.
Row orientation is less critical than row spacing. On level sites, orient rows to maximize length and minimize the number (and cost) of end posts. Most sites are not level, though. Do not contour rows around hills, as the trellises will be structurally weak. Low areas should be used as alleyways rather than for planting.
Sunlight interception by the vine canopies should be maximized. Research studies have shown that rows oriented in a north-south direction receive more sunlight, have better air movement among vines, and produce slightly higher yields than those oriented east to west. Thus, if other factors are equal, align rows as closely as possible to a north-south axis; however, row orientation should be paired with site constraints like topography and erosion potential. In some regions, strong south and southwest winds dictate row orientation more than light interception. In many vineyard locations, it is most important to orient rows across a slope to minimize soil erosion.
Take care to preserve topsoil, particularly if a site is to be terra-formed to eliminate gullies so the site if more amenable to grape production. Growers often have a dozer scrape high points into low spots to provide a more even surface for grape production. This leads to serious problems in variation in soil depth, above and beyond those already found on a slope. If terra-forming is to be done, scrape the topsoil from the vineyard and pile it away from leveling activities, if possible. After leveling the subsoil, return the topsoil to the vineyard with a more even distribution. Make every effort to reduce the variability in a site or at least blocks within the site. By doing so, the vines within that block will be more uniform, making management of that block easier.
Many decisions go into row spacing. A grower needs either to decide the row width and purchase the appropriate equipment to work within that width, or, if the grower has existing equipment, make decisions based on the dimensions of that equipment. In deciding row width, consider the height of the canopy. There should be a 1:1 ratio between canopy height and row width to avoid shading of the fruit zone, particularly in cooler growing regions. As an example, if the canopy height is planned for 6’, the MINIMUM row width would be 6’.
Row spacing needs to match vine vigor and the factors that influence vine vigor, such as soil type, cultivar, rootstock, and cultural management. Many factors, including experience with a cultivar on a site, determine the best row spacing and training system. Ultra high-density vineyard spacing should only be implemented on low vigor sites with low vigor vines. Many sites east of the Rocky Mountains are medium to high vigor, particularly where frequent rain occurs during the growing season.
Most trellises are constructed with 8-foot line posts set 2 to 3 feet into the ground, thus providing a 5' to 6'-high trellis supporting about 4 feet of canopy (for a VSP or similar system). Therefore, the row spacing should be no less than 6 feet, as row spacing should not be closer than the height of the canopy to minimize row-to-row shading of adjacent canopies. However, the size of conventional vineyard equipment, as well as vine vigor, often limits the minimal row spacing to 8 feet to as much as 13 feet. Consider equipment availability and operation carefully before deciding on row spacing. Use wider spacing (10 feet to 13 feet) on steeper terrain, or where you have a horizontally divided canopy training system such as a Geneva Double Curtain (GDC).
In-row vine spacing ranges from 3 feet to 12 feet, with 6 feet to 8 feet being most common. Spacing within the row will be determined by soil vigor potential, the climate in which the vines are grown, and the cultivar/rootstock combination. For example, use 8 feet to 10 feet between vigorous vines, such as those planted in deep, well-drained, fertile or irrigated soil. Use 6 feet between less vigorous vines, such as those planted in shallow soils. From an economic standpoint, close vine spacing (less than 4 feet) increases the yield per acre in the initial years of production. However, that accelerated return can be offset by higher costs for materials and labor. Closer vine spacing also complicates canopy management. On the other hand, wide vine spacing (more than 10 feet) can result in poor trellis fill. Therefore, a vine spacing of 6 to 10 feet is generally recommended for non-divided canopy training systems (e.g., VSP and high cordon).
Enough space should be left at the end of vineyard rows to provide room to turn equipment. Tractors with attached trailer-type air-blast sprayers require a minimum of 30 feet turning clearance. Rows longer than 500 feet should be divided with a cross alley to facilitate movement of machinery and personnel.
North Carolina Winegrape Grower's Guide, North Carolina State University
Vineyard Establishment, Iowa State University
Design Your Own Vineyard, Kentucky State University
Vineyard Design, University of Kentucky
Considerations & Resources for Vineyard Establishment in the Inland Pacific Northwest, Washington State University
Reviewed by William Shoemaker, University of Illinois and Sara Spayd, North Carolina State University