Preparing the Site
The first step in planting a vineyard, once the site has been selected, is site preparation which involves a number of pre-planting activities. This is the time when changes can be made to the site to improve soil conditions, water handling, and the overall efficiency of managing the vineyard.
Land clearing is any operation which includes the removal of excess undesirable vegetation or debris from a site, such as trees, shrubs, stumps, logs or rocks. Debris piles can be burned at the edges of the vineyard, preferably away from where vines are to be planted. The site should be mapped to identify intermittent streams, surface water runoff channels and steep slopes such as ravines.
Soil testing should follow land clearing, preferably the season before planting to allow time for correcting deficient nutrients and soil pH, if necessary. Soil analysis has some limitations, and research has shown that results may correlate poorly with leaf-tissue analysis and vine responses. Nonetheless, a good soil sample can reveal much about the relative levels of nitrogen, calcium, phosphorous, potassium, and magnesium in the soil as well as the need for lime or gypsum.
Soil Sampling Method
Take separate samples from areas where apparent differences in soil conditions exist as noted by differences in soil color or differences in the type of soil. Within the area used for a single sample, collect upwards of 20 subsamples from each depth using a soil probe or by using a shovel taking a thin slice of soil.
Soil Physical Limitations and Modification
Extensive soil modification is not always necessary to prepare a vineyard site for planting. Some soils are naturally deep and relatively uniform in texture and structure and do not require soil modification. However, some soils need modification because they have physical limitations commonly referred to as stratified soils, claypan soils, hardpan soils, plowpan soils, and clay-rich soils.
Stratified soils have horizons or layers with abrupt changes in soil texture. The layers interfere with the uniform drainage of water, causing zones of poor aeration that may restrict root growth. Modifying stratified soils to improve productivity requires mixing the soil layers with slip plows, moldboard plows and disc plows.
Claypan soils have an abrupt increase in clay content within a very short vertical distance (1 to 2 in., 0.5 to 2 cm) in a soil horizon. This increase in clay content restricts water movement downward, thus restricting aeration and root growth in the subsoil.
Hardpans soils are similar to claypans, except the soil particles are cemented together by hard mineral matter (silica) that do not soften, even when wet. This hardened layer is usually an absolute barrier to root growth and water percolation.
Soils with plowpan soils can be found in some vineyard sites. Plowpan soils are caused by tilling a soil at the same depth repeatedly or by repeated heavy traffic, particularly when soils are relatively wet.
Clay-rich soils may be found in some orchard sites. These soils typically contain 35 percent clay and appear relatively uniform throughout the profile with subtle changes in soil texture, structure, and hardness.
The next step is subsoiling (often called ripping) to break up hard pans or compaction layers to allow both easy and rapid root penetration and water infiltration (See Figure 5.1). The winged shank blade is the main piece of equipment used for ripping which helps lift the soil behind the tractor and distribute it evenly
Time for Subsoiling
Generally there are only two periods of the year when this condition can be met: late fall (sufficient rainfall to moisten but not saturate subsoil) and late spring (sufficient drying out but not desiccation of subsoil). Only at these times will the soil fracture correctly and yield fine fragments necessary for optimum root penetration.
Soils are usually ripped with a D8 cat or larger to a depth of 1 yard (0.9 m) using a 1.6 yard (1.5 m) shank. The subsoil is usually ripped in one direction along the intended vine rows. If necessary lower the shank working depth and rip on the same lines more than once, going progressively deeper with each pass.
The next step is tillage, which is a sequence of operations traditionally or most commonly used in a given geographic area to prepare the soil for transplanting the vines. Equipment used to break and loosen soil may include plows, disc harrows, and harrows.
A wine grape grower has the choice between two plow types, the moldboard or the disc plow, each adapted to certain soil characteristics.
Disc harrows are used to reduce the size of larger soil clods by fracturing them with cleavage and pressure (See Figure 5.3). Disc harrows are general-purpose tillage implements consisting of gangs of concave discs.
The function of the harrow is to further reduce the size of soil clods left after discing, to smooth the soil surface, and to do small-scale leveling.
An effective weed management program is a necessary part of any wine grape production enterprise. Weeds compete with vines for water and nutrients, and may have allelopathic effects on vine growth. Weed control is particularly important during vineyard establishment, not only to encourage survival of young vines, but also to help hasten them into production. Even after the vines are well established, weeds can compete for water and nutrients, reduce yields, and interfere with harvest.
Weed Management without Herbicides
One weed management method to keep the vineyard floor free of weeds using shallow cultivation. Frequent cultivation lowers annual weed seed populations in the soil, thus reducing weed growth.
Weed Management with Herbicides
Herbicides can be a valuable tool in a weed management program. Weed seedlings and established weeds can be controlled either with preemergence or post-emergence herbicides (e.g., glyphosate) before planting the vineyard.
Several factors determine the need for artificial drainage, including slow soil permeability, flat or depressional topography, restrictive layers at shallow depth, and periods of excessive precipitation. Soil factors that cause a soil to experience drainage problems include the texture (higher clay content causes slower permeability), soil structure (a massive structure without macropores causes poor percolation), compaction of surface or subsurface soil by vineyard equipment, and sealing of the soil surface and depositional crusts in lower-lying areas.
Tile and Pipe Drainage
Subsurface pipe drainage may be used in deep permeable soils that underlie compact impervious layers near the root zone where the groundwater is high. This system can also be used to drain naturally poorly drained soils.
Mole drains are used on heavier, low permeability, clayey soils where downward movement of water through the soil profile is slow. The mole drains are unlined cylindrical channels formed using a mole plough. The mole plough comprises of a cylindrical foot attached to the bottom of a vertical leg.
A cover crop should be sown immediately after ripping, particularly on steep land. A variety of perennial and annual grasses and forbs (broadleafed plants) can be used for cover crops as either single-species or multi-species mixes depending on the grower’s needs.
Windbreaks offer many benefits to many vineyards reducing leaf tatter, sandblast desiccation, and wind damage to growing tips. Protected grapevines produce greater leaf area with larger leaves, longer shoots, higher pruning weights, increased vine capacity, longer internode length, improved pollination and fertilization, and improved berry set.
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