Soils

Soil is defined as the naturally occurring mineral or organic material on the earth’s surface capable of supporting plant growth. The type of soil formed in any one place is the result of the interaction of climate, organisms and topography acting on the soil parent material over time. Soils display a continuum of properties and reflect the variation of these soil-forming factors.

Vine health and productivity is dependent on a healthy root system. Roots operate most effectively in neutral, deep, well-drained, and well-aerated soil with good organic matter and an adequate supply of nutrients. Grape vines are deep-rooted plants requiring adequate soil depth and are not suited to shallow soils.

Most soils in the Okanagan - Similkameen area have developed under grassland – forest vegetation and semi-arid climatic conditions. In the grasslands, organic matter is mainly added to the soil by the decomposition of grasses and herbaceous plant materials and ac-cumulation in the A horizons of these soils. Under these conditions, Brown and Dark Brown Cherno-zemic soils are prevalent on well and rapidly drained sites. At higher elevations, within the forested area relatively cooler conditions persist and Brunisollc soils occur on well and rapidly drained sites. In these soils, organic matter additions to the topsoil are limited and well structured and deep A horizons are either thin or absent. Under the same climatic conditions the soils also show differences due to both texture and mineral composition. Luvisolic soils have developed in clay rich par-ent materials in which clay is translocated to a subsurface layer. Gleysolic soils have developed in poorly drained areas on a variety of parent materials from clay to sand. Saturated conditions are reflected in these soils by dull gray colours and/ or iron mottles. Regosolic soils are ‘young soils’ and in the map area are confined mainly to the Okanagan and Similkameen river flood-plains and to a few other steeply sloping sites. Organic soils have developed in very low areas which are usually moderately decomposed and range from shallow to deep.

Due to non-uniform glacial and river deposits of gravels and sand, the sub-surface composition of some soils can vary greatly. It is important to take these factors into consideration, when designing the irrigation system, since these sand or gravel banks can greatly impact the water holding capacity of the soil in the affected area. Often areas of poor vine vigour can be traced back to gravel deposits, which are not visible at the soil surface. For irrigation water to penetrate the gravel, the surface soil must first be brought to full field capacity!

SOILS OF THE OKANAGAN AND SIMILKAMEEN is a comprehensive study map-ping the soils of the Okanagan and Similkameen Valley. This publication is available online at http://sis.agr.gc.ca/cansis/publications/bc/bc52/.

Soil Survey

A detailed soil survey should be completed prior to vineyard development. The goal of the survey is to identify where changes of the soil type occur and characterize the physical properties of each different classification. The vineyard blocks should be designed based on the changes in soil type. Each block or irrigation valve should contain the same soil type in order to maximize vineyard uniformity. Once the survey is complete a soil sample from each region with a different soil type can be taken. The soil sample will determine the physical, chemical and biological properties of the soil.
The survey should be performed by a qualified professional. The results of this survey are used to decide what irrigation system, rootstock, and variety is most appropriate for the specific soil type. This process should be performed the year before planting, prior to ordering vines.

Soil Amendments

On the completion of the soil survey amendments can be added and incorporated into the soil where necessary. The soil sample results will determine what soil amendments may be necessary. Recommendations for soil amendments will be given along with the soil analysis but should be reviewed with a qualified professional. For more information on amendments see Section 4.3 Nutrition in this production guide.

Land Preparation

The first step in developing a vineyard is to remove any existing vegetation or structures that obstruct development. Obstructions such as trees, posts and rocks need to be removed. Once removed, light cultivation and leveling with a tractor to remove any irregularities will leave a relatively even surface. Low areas which may be prone to frost should be filled in at this time. Mounds or hollows left will become a permanent fixture once the plants and posts are in. The land should be even enough to facilitate smooth tractor operation. During the design of the vineyard roadways and the perimeter of the blocks should be relatively level if possible to ensure safe equipment operation. Significant movement of soil in preparation for planting is generally not recommended. Most of the soils in the Okanagan have limited top soil and organic matter.

Significant land alteration changes the structure of the soil horizons, nutrient availability as well as the drainage characteristics of the soil. However, in some cases change to the slope of the land is necessary to facilitate production. This is usually due to frost pockets, gullies, steep slopes, or other impediments. It is important to consult with a professional prior to any land movement and use a reputable contractor that is experienced in land preparation.

Pre Plant Cover Crops

There are a number of advantages to growing a cover crop before planting: cover crops can improve soil structure, contribute some nutrients (mainly potassium and possibly nitrogen, depending on crop choice), improve water holding capacity of the soil and suppress weed growth. Cover crops can add considerable amounts of organic matter, which provides food for micro and macro organisms in the soil. Many soil organisms help to make nutrients more readily available to plants.

If the cover crop is planted in the fall, rye or winter wheat, possibly in combination with a winter annual legume (e.g. hairy vetch or winter peas, which need to be cut or incorporated into the soil before they start to set seed in late spring/early summer), produce a fair amount of bio mass and can help in suppressing weed populations. If land leveling or movement of the soil is required it is generally recommended that the land be left fallow for at least 1 year in order to grow a cover crop to improve soil conditions.

If cover crops are planted in spring, after risk of frost is past, there are a number of suitable plants: buck-wheat together with oats and a legume (summer vetch, crimson clover, berseem clover, persian clover, etc.) pose little risk of becoming weeds in the interior of BC because of their limited winter hardiness. Oats contain less lignin than most other cereal crops and do not tie up as much nitrogen when they break down in the soil. Annual rye grass grows very fast and can also be used in mixes with a legume.

Nitrogen Contribution of Cov-er Crops

Many legume cover crops can contribute considerable amounts of nitrogen to the soil through nitrogen fixing bacteria on the roots and through the protein content of the biomass. The actual amount will how-ever vary with soil conditions, irrigation, species of legume, and timing of incorporation. For maximum nitrogen contribution seeds should be inoculated with the appropriate rizobia bacteria and incorporated into the soil at bloom time. See also chapter 4.5 for more information.

Site Development

A site plan is an invaluable tool in planning a vineyard. The position of buildings, irrigation, power supply, roadways and row direction and length should be indicated on a scale drawing.

Buildings must include storage facilities for equipment, lunchroom and restroom facilities, a ventilated pesticide storage area and a fuel tank storage area. A separate area for sprayer loading and sprayer wash down is required. Check WCB regulations and local by-laws for suggestions on construction and ventilation requirements. Potable water for employees and an emergency shower and eyewash station should be close to the chemical loading area

When establishing an irrigation system ensure the supply is adequate to fulfill your needs during the highest demand period of the summer. Irrigation should be delivered to an area convenient for distribution to the blocks of the vineyard with power for pumping, filtration and automated control devices. The plan should address the type of irrigation to be employed and whether frost protection is anticipated. The soil survey is an integral part of the planning of the irrigation system since variations in soils de-mand varying volumes of water. Future water availability should be considered when choosing an irrigation system. Drip systems and under canopy micro-jet systems are more efficient in supplying water than overhead systems, and require smaller pump-ing systems. Use an experienced and reputable professional to design the vineyard irrigation system.

The size of vineyard blocks and the row directions of the blocks must be determined prior to the design of the irrigation system. Once the row direction and width is established the rows can be laid out and if necessary deep ripping performed. Ripping is best performed when the soil is dry and is quite useful in heavy or layered soils but not of much use in gravely and sandy soils. Ripping clears a way for the plant to develop a rooting system, aerates the soil, and makes it easier to plant vines and pound posts.

Row Direction

In general rows should be planted north-south if the slope of the site allows. North-south row orientation allows for the canopy to maximize the amount of solar radiation it intercepts. The fruit on the east and west sides of the canopy will develop at the same rate, increasing the vineyard uniformity and quality. East-west row orientation exposes the southern facing fruit to more heat and sunlight which results in uneven development between the north and south sides of the canopy. In areas with very high wind speeds the row orientation should be parallel to the wind in order to minimize damage to the canopy. In areas with a high frost risk the rows should run parallel with the slope to increase air drainage.

Vine Spacing

The decision on plant density should be determined by how well the vine’s roots will exploit the soil.

There is little evidence to suggest a higher density results in a higher quality wine. However, the higher densities do allow for a lower yield per plant to achieve production goals and this could offer a greater chance of survival from a severe winter.

Vineyard establishment costs, as far as vine spacing is concerned, are influenced more by the number of rows per hectare than by the number of vines per hectare. The cost of vine planting and training is influenced by vine density, but these costs are minor. Between-vine spacing in the row should be designed to spread the wood of a vine on a trellis in such a way that the vines produce the de-sired yield without crowding. The pruning system (cane or spur) that will be used will influence the in-row spacing. Cane pruned vines will need room for 12 to 14 bud canes when laid along the wire, with 10 cm between cane ends to prevent shoot and fruit crowding. Cordons with spur pruning do not need as much space on the wire.

Between row-spacing of the present acreage varies between 2.3 meters to 2.7 meters and between plant spacing from 0.6 meters to 1.5 meters. The most common is 2.4 meters by 1.2 meters.