Two soil-management systems are now in general use in Midwestern vineyards. Many growers cultivate between the rows during the growing season and plant a cover crop over winter. A more recent system is to maintain a permanent sod cover between the rows. In both cases, weed growth under the trellis is controlled by chemicals or tillage.
Vineyards planted on shallow soils or the lighter soils in the lake plains areas usually respond best over a period of years to the cultivation plus cover-crop system. Those planted on the fine-textured soils and those on the more sloping sites subject to soil erosion may respond more favorably to the system of permanent sod cover between the rows. However, with care, almost any vineyard can be maintained under either system.
The kind of winter crop cover selected is relatively unimportant. Rye and ryegrass are most common, and both are satisfactory. Seed is planted in August or early September. Satisfactory seeding rates are two bushels per acre for rye seeded in early August, or 20 pounds per acre of ryegrass seeded in July. A light fertilizer application, such as 3–12–12, at the rate of 200 to 250 pounds per acre can be made at seeding time. When seeding, avoid scattering seed in the vine rows.
Disk the overwintering cover crop down in early spring before it competes with the grapevines. For rye, competition with vines begins when rye reaches a height of 1 to 2 feet, and for ryegrass, when seed heads just begin to appear. However, growers should never disk when the soil is wet enough to deteriorate the structure. Disk only enough to knock down the cover. Excessive disking not only wastes labor, but also can damage the soil structure and create compaction zones.
Cultivate between vine rows during the summer only when necessary to control weeds. Cultivate as shallow as possible, but deep enough to destroy weeds or grass beneath the trellis. Deep cultivation or plowing between rows will do more damage than weed growth because of loss of soil organic matter and soil structure.
After the planting year, avoid excessive cultivation in the vine row that can injure shallow roots and increase soil compaction. Chemical weed control is recommended under the trellis.
Competition from a cover crop during spring and early summer can reduce yields. The extent of yield reduction depends on the degree of competition between the cover crop and the vines for soil moisture and nutrients. Because nutrients can be applied with fertilizers, the primary competition is for water.
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| FIGURE 109. A permanent sod cover between rows is recommended in erosion-prone vineyards. |
A permanent-sod cover between vineyard rows is desirable in the Midwest (Figure 109). This practice is recommended in vineyards where soil erosion is likely to be moderate to severe under summer cultivation.
Bluegrass is recommended for this purpose. It is suited to Midwestern environmental conditions and competes less severely with grapes than deeply rooted cover crops. A new grass mixture marketed under the trade name Companion Grass also is gaining acceptance in vineyards and orchards because of its slow-growing characteristics. Companion Grass is a mixture of Elka perennial ryegrass and Ensylva creeping red fescue. Avoid deep-rooted crops such as tall fescue, timothy, and other vigorously growing grasses.
Seeding of bluegrass is more successful in the fall than in early spring. The ideal time is early September. If the vineyard has been under summer cultivation, bluegrass or Companion Grass may be seeded following the last cultivation at the rate of 20 to 30 pounds per acre. If the vineyard has not been under cultivation, these grass seeds may be broadcast following a light disking that does not destroy existing sod. Avoid broadcasting seed under the trellis.
Mow the grass cover as needed, directing the clippings to the row middle, away from grape rows, and leave the clippings on the vineyard floor. Vineyard fertilization usually can support a good sod cover. However, if poor sod results, take a soil test, and follow the recommended fertilizer practice.
Growers may experience reduced crop yields with a permanent cover-crop system on lighter, sandy, or gravelly soils. This probably results from the reduced available moisture in these soil types. Keeping the sod short will reduce competition.
Mulching has been used in soil management for grapes, although it is not generally accepted. Mulching has several advantages over cultivation plus cover crops. Mulching:
In vineyards where vine vigor is low, mulching and other sound soil-management practices can economically and effectively boost vigor. In this situation, growers can achieve the most favorable results of mulching.
However, mulch may have some disadvantages in certain situations. Vigorous vines may require a longer season to mature fruits with optimum soluble solids (°Brix) content than vines of less vigor. The problem arises when growers try to reduce the vigor or amount of growth on over-vigorous vines under continuous mulch. Often, two to three years are required to reduce annual vine growth to a more desirable level, even when balanced pruning is followed.
Heavy mulching of poorly drained soils should be avoided because it could actually increase excess soil moisture in the root zone. Mulching also may increase fire and rodent hazards.
Most organic materials such as straw, hay, corn cobs, sawdust, composted grape pomace, or fine wood chips will serve satisfactorily in the vineyard. The mulch may be applied to the entire vineyard floor or confined to a 4- or 5-foot band beneath the trellis. If erosion control is the primary goal, adding mulch to row middles generally is effective. The depth of the mulch can vary from 2 to 10 inches. The necessary mulch depth depends on the quantity available, density of the material used, and the cost. Generally, 6 to 8 inches of loose straw or 2 to 3 inches of sawdust are adequate. Bales of rolled hay also have been effective in vineyards, but can be a source of weeds, especially perennials like Canada thistle.
Once the initial mulch has been established, annual additions are necessary to maintain the desired depth. In general, a ton of straw is required for an inch of mulch over one acre. Other materials may require varying amounts to form an inch of mulch, depending on their density and bulk.
Grapes can be grown successfully over a wide range of soil pH conditions. They perform best where soil pH is between 5.5 and 6.5. Vineyard fertilization often has fewer problems and may be less expensive where the soil pH is maintained in that range. Periodic soil testing is necessary to determine the soil pH and liming requirements. Lime should be applied only when soil analysis indicates a need.
Research has shown that potassium deficiency can be intensified by dolomitic limestone, which is high in magnesium. Excessive applications of calcium limestone also can result in manganese deficiency. The deficiency occurs because soil manganese becomes more insoluble and less available to roots when the pH is raised to near 7.0 or above.
Applying dolomitic limestone can help correct magnesium-deficient vineyards. Dolomitic limestone also can be used to reduce soil potassium levels if magnesium is above recommended levels. For more information, refer to Ohio State University Extension Bulletin 458, Fertilizing Fruit Crops.