How much water do grapes need? Do grapes like alkaline or acidic soils? How do I grow bigger grapes? These are some of the obvious questions whenever a farmer decides to grow grapes. Let’s try to look at the answers to these questions.
Grapes can be cultivated in variety of soils including sandy loams, sandy clay loams, red sandy soils, shallow to medium black soils and red loams. The soil should be well drained, having good water holding capacity and devoid of any hard pan or impervious layer in the top 90-cm, with water table at least 6.5m below.
Grapes can also be grown successfully over a wide range of soil pH (4.0-9.5) however, soils having pH range of 6.5-8.0 are considered ideal.
Grapes often make more clusters of grapes than the branch can properly nourish. If all the clusters try to develop, fruits are small and often poor in color and sweetness.
Just after the flowers have finished blooming and the flower parts are falling off, look over your grapevine and remove any forming clusters that are poorly shaped, too big or too little. Then look at each individual branch and estimate how many bunches each shoot should successfully nourish.
For larger grapes, leave few clusters. In young grapevines, leave just one cluster per branch. You can remove clusters to improve grape size if you do it before the developing grapes start to turn color.
Grapes generally require a hot and dry climate during its growth and fruiting periods. It is successfully grown in areas where the temperature range is from 15-40 C. High temperatures above 40 C during the fruit growth and development reduce fruit set and consequently the berry size. Low temperatures below 15 C followed by forward pruning impair the budbreak leading to crop failure.
The fruitfulness of buds is influenced by light. Light intensity of 2,400-ft. candle is essential for optimum growth. However, low light intensities during the active growth stage (45-75 days after pruning) and fruit bud formation adversely affects the crop. It is most successfully grown at elevations ranging from 200-250m above sea level.
Area with annual rainfall not exceeding 900mm well distributed throughout the year is ideal. However, rainfall during flowering and fruit ripening is not favourable as it leads to the spread of downy mildew disease. High atmospheric humidity is detrimental during vegetative growth and fruiting. At a high humidity the vegetative growth of vines is vigorous which affects the fruit size and quality. Similarly high humidity during 30-110 days after forward pruning favours the development of fungal diseases.
HOW TO PLANT GRAPES
- Plant dormant, bare-root grape vines in the rainy season.
- Construct a trellis or arbor before planting. Grape vines will need to be trained to some sort of support to grow upward. This will also cut the risk of disease.
- Most grape varieties are self-fertile. To be sure, ask when you are buying vines if you will need more than one plant for pollination.
- Before planting grapevines, soak their roots in water for two or three hours.
- Select a site with full sun. If you don’t have a spot with full sun, make sure it at least gets morning sun. A small amount of afternoon shade won’t hurt. Your soil needs to be deep, well-drained, and loose. You also need good air circulation.
- Space vines 6 to 10 feet apart .
- For each vine, dig 12 inches deep and 12 inches wide. Fill with 4 inches of topsoil. Trim off broken roots and set the vine into the hole slightly deeper than it grew in the nursery.
- Cover the roots with 6 inches of soil and tamp down. Fill with the remaining soil, but don’t tamp this down.
- Prune the top back to two or three buds at planting time.
- Water at time of planting
CARE FOR YOUNG VINES
Immediately after planting, prune the vine so that just the most vigorous cane is left.
Fertilize with 1/2 to 1 ounce of nitrogen during the first growing season when the buds begin to break open. A balanced fertilizer, such as a 10-10-10 ratio fertilizer containing 1/2 to 1 ounce of nitrogen, works well.
Apply the fertilizer to the surface of the soil, staying at least eight inches away from the vine trunk. During dry weather, water enough to keep the soil moist but not soaking wet. During the second year growing season, fertilize with 1 to 1 1/2 ounces of nitrogen.
Older grape vines generally only need watering during extended periods of dry weather.
Further thinning of the number of grapes growing on each cluster makes individual grapes larger.
You’ll notice that some table grapes have so many fruits in a cluster that they get pressed together and are limited in their growth. Give grapes a chance to grow larger and to get more plant nutrients and water per grape by shortening the cluster.
Take off the bottom half of the cluster, leaving four to five side branches near the top. Since these branches grow sideways from the cluster’s main stem, they have room to hold fruit without crowding.
SYMPTOMS OF WATER STRESS
When water demand of the grapevines is higher than supply, drought stress occurs. Often, drought stress is associated with heat stress during the hot summer months.
Varieties differ in their response to water restrictions .
A trellis is needed to support the foliage and fruit since the grapevine does not have a rigid trunk.
Not only does the trellis support the weight of the fruit, but it spreads the grape canopy ensuring sunlight penetrates all parts if the vine in addition to promoting good air circulation which is essential for keeping down the incidence of disease. A trellis system can be as simple as a single wire in a high cordon system to as complex as a number of catch wires at various heights as in the case of a Lyre trellis.
The types of trellis systems used worldwide are numerous, and no single system is appropriate for all situations. Deficiencies in design, materials or construction can result in deficiencies in vineyard performance leading to excessively high maintenance costs throughout its life cycle. Trellis construction represents a major investment in both time and money.
PRUNING AND TRAINING GRAPEVINES
Profitable grape production requires that grapevines be managed so that a large crop of high-quality fruit is produced each year.
Grapevines must be pruned and trained annually to achieve this goal.
The term dormant pruning refers to the annual removal of wood during the vine’s dormant period. Grapevines are pruned primarily to regulate the crop but also to maintain a vine conformation consistent with the desired training system. Pruning is used to selectively remove unsuitable or extraneous canes, retaining a small number of good canes. Canes are carefully selected to serve two functions:
- produce fruitful shoots in the coming season,
- Produce healthy shoots from which a good fruiting cane can be selected in the next dormant season.
Training positions the fruit-bearing wood and other vine parts on a trellis or other support so as to shape the vine. The basic goal of training is to maximize production, facilitate vine management (i.e., spraying, tillage, pruning, harvesting), improve canopy microclimate and to support the mechanical load of the vine.
MANAGING NEMATODES IN VINEYARDS
Nematodes are microscopic, unsegmented roundworms present in most soils that feed on vine roots. Nematodes are a major economic problem in every major grape production region in the world.
Plant-parasitic nematodes can cause direct and indirect damage to a vine. Nematode feeding can cause direct damage by stopping root elongation, killing plant tissue, changing root growth patterns, and by removing plant nutrients.
Their feeding patterns fall into two categories: some feed externally on roots (ectoparasitic nematodes), while some penetrate into roots and feed internally (endoparasitic nematodes).
Indirectly, plant-parasitic nematodes can damage plants by vectoring viruses or by increasing the severity of other plant diseases, such as Pythium, Fusarium, Rhizoctonia, and Phytophthora.
Nematodes like other pests take advantage of vines that are under stress as a result of management practices and/or other biological pressure.
If grapes aren’t ripening, pinch back some of the foliage to let in more sunlight. Grapes will not continue ripening once picked from the vine. Test a few to see if they are to your liking before harvesting.
Grapes are ripe and ready to harvest when they are rich in color, juicy, full-flavored, easily crushed but not shriveled, and plump. They should be tightly attached to the stems. Sample different grapes from different clusters, and the taste should be between sweet and tart.