The quality of wine depends largely on vine management. Here are some tips for achieving optimal returns from new vineyards.
Proper soil preparation is very important when establishing vineyards. Soil profile holes should be dug to determine the soil type and structure, to see whether any restrictive layers – such as clay or rock – are present and to determine what type of soil preparation – such as ripping, subsoil and so forth – is necessary.
Take soil samples at depths of 0 mm to 300 mm, 300 mm to 600 mm, and 600 mm to 900 mm, and send them to a reputable laboratory for analysis. Use the results to make chemical corrections – for instance, through the addition of lime, phosphate, potassium, and/or gypsum.
Farmers should remember that vines remove nutrients from the soil. Leaf and soil samples should therefore be taken periodically after harvest to determine the nutrient status of the soil and vines.
Based on these results, a fertilisation programme should be compiled by an expert. Average shoot length gives a good indication of whether vines suffer nitrogen deficiency (see table 1).
Although soil conditions and vineyard cultivation practices play a big role in the water requirements of wine grapes, climatic conditions have the greatest effect.
Other factors, such as the age of the vines, water quality and the season, will also determine how much water will be needed.
In areas that have a high average annual rainfall (mainly in winter), dryland cultivation is possible on deep, fertile soils that have good water-holding capacity. Depending on the season, supplementary irrigation is needed in these areas.
Most other areas have to be irrigated intensively. Depending on the soil type, in cool areas grapevines need 380 mm of water in the growing season to ripen and up to 1 140 mm in warm areas.
It’s crucial that enough irrigation water be available during the vegetative growing season. Depending on the soil type, either drip or micro-jet irrigation is recommended in these areas.
- Sandy soils have to be irrigated more frequently than soils with a good water holding-capacity.
- Irrigation frequency can be determined by measuring the soil water content with tensiometers or other soil moisture probes.
- If none of these are available, a spade or an auger can be used to determine the soil’s dampness and whether the vines need more water.
Grapevines are creepers and need to be pruned annually to ensure good yields and form a healthy vine structure.
Wine grapes can be established as bush vines, in which case no trellising is needed and the structure is developed in the form of a cup. This type of establishment is mainly used for dryland vineyards.
Irrigated vineyards are trained on a variety of trellis systems, depending on soil fertility, cultivar, vine vigour or wine goal. These trellis systems consist of a variety of horizontal hedge-type systems (Four Stand Hedge, Perold, etc) and larger vertical systems (slanting, factory, gable, etc). The latter is mainly used for high-yielding cultivars to produce lower-quality wines.
Pruning is important for developing a sound cordon system and developing bearers that will enable the vines to produce good yields over their life-span of about 20 years. Under SA’s climatic conditions, most wine grape cultivars are pruned to two-bud short bearers because there’s enough sunlight to enhance bud fertility.
These bearers need to be spaced 12 cm to 15 cm apart and must be cut back each winter to the lower budded shoot to prevent building up.
Correct pruning practices results in easier suckering and canopy management that will ensure good ambient sunlight penetration within the canopy, and optimise micro-climate conditions in the canopy for producing high-quality grapes and wine. This also creates a more open canopy that enhances the application of fungicides.
PESTS AND DISEASES
Wine grapes are prone to many diseases and pests, so a strict spraying programme should be followed. Downy mildew, in particular, causes severe damage to vines and yields.
Farmers should ask one of the agricultural chemical companies to recommend a pest management programme that adheres to the Integrated Production of Wine Grapes guidelines (IPW). See the IPW web site at www.ipw.co.za for more information.
It’s also important to control soil-borne diseases. Using resistant rootstocks would do away with the need for chemical control.
- It’s important, when new vineyards are planted, that the farmer first consult his local co-operative cellar and viticulturist for recommendations regarding cultivars.
- The market will dictate which ones should be established.
- The farmer should also secure a market before starting planting.
- Establishing and managing a wine grape vineyard is expensive
- As wine grapes have a productive life-span of 20 years, provision must be made for replacing 5% of the vineyards every year.
- This article was written by Danie van Schalkwyk from the SA Agricultural Research Council Infruitec-Nietvoorbij and first appeared in Farming SA.