Table grape growth and yield are restricted on sites with very heavy clays or very shallow soils, poorly drained sites, high salt concentration and extreme pH; because nutrients cannot be sufficiently available.
Supply of correct nutrients positively affects table grape yield.
Production of higher yield comes from controlling the number of grape bunches and size of grape berries. Even berry size is highly desirable to ensure even grape maturity in order to maximize production per area. Physical or nutritional crop manipulation is important to ensure even berry size and consistent maturity to meet market specifications.
Nitrogen is one of the most important elements governing table grape yield. It promotes strong, early growth and bunch and berry weight. However too much nitrogen can delay maturity and increase disease risks as the grapes near harvest.
Potassium is needed in large quantities and throughout the season, particularly during fruit fill for sugar assimilation. In trials conducted in Chile, very high rates of potassium (600 kg/ha of K2O) nearly doubled yields compared to untreated vines.
Calcium is important for early crop development and healthy growth, leading to high grape crop yields.
Magnesium is needed to maintain photosynthesis and the synthesis of proteins required for high yields.
Of the micronutrients, boron and zinc are the most important for fruit set and final yield in table grapes, and need to be available at higher quantities than other nutrients.
Iron and to a lesser extent manganese, are important for early leaf production and photosynthesis to ensure better berry development and table grape yield.