SA offers unique growing environments for Sun World varieties. By Michele Melillo, Sun World
Extending from Limpopo to the Hex River Valley, going through the Orange and Olifants River regions, Sun World varieties are planted in a wide range of soils and climates and are subjected to different cultural practices.
There are several challenges and opportunities linked to having the production of these varieties spread over several climatic areas.
In the last few years, changing climatic patterns have presented South African table-grape producers with significant challenges. A higher incidence of unseasonal rains has caused crop loss and lower fruit quality, resulting in higher farming costs.
Agriculture requires continuous adapting of farming practices, to changing climatic conditions. Adoption of more precise practices (nutrition, canopy management and irrigation are among the most important) and the use of protective measures (such as wider and more precise use of plastic covers) will become necessary for the South African table-grape industry to remain sustainable and competitive in the global market.
Potential cultivation challenges for 'Sugra35', with tips on how to overcome them
Read MoreProduction
Vigour Management 'Sugra35', marketed under the AUTUMNCRISP® brand, has a peculiar growth pattern. Shoots have a low growth rate earlier in the spring and as soon as soil and air temperatures increase (usually around flowering time), vigour resumes, producing strong shoot growth. This growth pattern has important consequences in vigour management, particularly with pruning and nutrition.
Pruning Correct pruning load greatly helps to manage vigour, reducing labour for canopy management and maintains optimal light diffusion and ventilation. South African producers, historically accustomed to varieties with low fertility and high availability of workers, are used to pruning with a high number of buds/ha (>120-150 k/ha). Excessive bud loads lead to slower growth right after bud break, increasing the risk of poor vigour before bloom. This mainly translates into thin shoots (<8 mm at the third internode), which is not optimal for reaching good fruit quality. Under most conditions in SA, 'Sugra35' should be pruned with an average of 90 – 110 k buds/ha. An excessive number of shoots per hectare decreases light diffusion and ventilation.
Nutrition It is important to understand the natural behaviour of the variety. The correct nutrition plan is crucial for preserving vine balance and allowing the plant to optimise yield and quality. 'Sugra35', although a rustic variety that performs well in suboptimal growing conditions, performs better with the correct nutrition plan.
The initial slow growth (in many cases aggravated by high bud load or cold springs) may persuade producers to increase the units of nitrogen (N) applied before bloom, creating a surplus availability of N at bloom when the vigour resumes. The excessive vigour is expressed by excessive lateral growth creating poor light and ventilation conditions.
It's also important to control the vigour so that shoot tip growth is slow after veraison. Excessive application of N delays sugar accumulation, increases vine susceptibility to diseases, and decreases fruit quality at postharvest. Most of 'Sugra35' vineyards in SA with an average crop load of 30 – 35 tons/ha, require a range of 40 – 60 N kg units/ha. It is extremely important to continuously monitor the soil and vine nutrition status through soil and petiole analysis. Sun World Technical Support (GTS) can provide optimal nutritional advice for its varieties.
Fruit Quality
Irrigation Water management is the most crucial practice in vineyards. All varieties have different irrigation patterns, and it is very important to have the correct tools (soil and vine) to check vine water consumption. Sun World Technical Services is focusing on building optimal irrigation curves for its varieties in the different regions of SA. Specific focus is on avoiding excessive irrigation close to harvest, which leads to:
- reduced sugar accumulation
- increased risk of cracking
- poor postharvest quality.
Light Correctly managing vigour through nutrition, pruning and canopy management allows for optimal light distribution in the vineyard. All Sun World varieties enjoy good light distribution, particularly between veraison and harvest. Excess shade is always detrimental to fruit quality. In 'Sugra35' we aim to keep the LAI (Leaf Area Index) after veraison between 3 and 4 under the vine and 1.5 and 2.5 between vines. The objective, between veraison and harvest, is to have high diffuse light in the vineyard and protect the clusters from direct sunlight.
Crop Load All Sun World varieties have been bred for high fertility and in most South African conditions, Sun World varieties easily reach economically sustainable crop load. Overcropping is a potential challenge for fertile varieties, where producers need to draw a fine line between economic return, a sustainable crop, and climatic patterns that affect the crop forecast. Excessive crop loads lead to risk of Bunch Stem Necrosis (a problem commonly found in South African vineyards), lower berry size and unevenness, delay in sugar and colour accumulation, and poor postharvest quality.
Sun World's Global Technical Services team provides technical support to more than
2 000 licensed producers in >15 countries, and Sun World International LLC is a global variety development and licensing business. The company mission is to drive the growth of fruit breeding, varietal development, licensing and agricultural technologies.
The California-based company has a network of licensed producers and marketers and maintains offices in the US, Europe, Australia, South America, Israel, North Africa, and SA.
For more information contact:
Michele Melillo, VP of Global Technical Services (GTS), at mmelillo@sun-world.com
Robey Leibbrandt, GTS Agronomist, rleibbrandt@sun-world.com
Robert Oosthuizen, GTS Agronomist, roosthuizen@sun-world.com
Tharien Hansen, GTS Agronomist, thansen@sun-world.com
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