Balancing yield and quality in grapes requires a balanced nutrient management approach that considers appropriate soil and foliar applied nutrition to meet crop demands. Primary and secondary nutrients are required in the greatest amounts and micronutrients are typically required less, though just as essential. Nitrogen, phosphorus, potassium, calcium, and magnesium are critical primary and secondary nutrients to consider for a successful crop and healthy vine.
Nitrogen is a key component of amino acids, proteins, chlorophyll and other cell constituents, all of which are essential for crop growth and development. Depending on overall crop goals, typical nitrogen demand ranges from 30-50 pounds per acre. An appropriate nitrogen balance is critical. Too much nitrogen can result in overly vigorous vines later in the season that contribute to shading of the crop and subsequent delays in maturity. Too little nitrogen can result in poor shoot growth and subsequent sunburn in addition to yield reductions. The source of nitrogen can also influence cation uptake of elements like potassium, calcium, and magnesium, and contribute to changes in soil solution pH.
Nitrate carries cations with it. Ammonium uptake hampers cation uptake.
Nitrate nitrogen improves plant uptake of potassium, calcium and magnesium.
Phosphorus is essential for plant metabolism, energy transfer, and transport of photosynthates. It has a direct effect on yield and quality. Deficiencies can result in reduced growth and berry weight, and induce premature ripening. It can also hinder the overall production and utilization of carbohydrates.
Potassium is involved in the active translocation of sugars from the leaf to the fruit. Thus, it has an important role in determining fruit quality, brix, and yield. Grapevines have a relatively high potassium requirement compared to nitrogen with over 1.5 times the removal per ton of grapes. When potassium is properly balanced with nitrogen, plant growth and vigor is well managed and fungal disease incidences like Botrytis have shown reductions.
Calcium is a key component of strong cell walls and membranes and supports optimum plant health by regulating stress responses. Calcium, along with potassium, regulates the opening and closing of the guard cells around the stomates in leaves. Calcium’s immobility in the plant requires periodic supplementation to maintain adequate levels in the vine. Plant tissues that lack sufficient Ca lose the ability to regulate the stomates and plants can become overheated. When plants overheat, the current crop suffers reductions in weight and quality and stress can compromise next year’s crop potential.
Magnesium is needed for many processes including the transfer of energy, protein synthesis, and chlorophyll production. As much as 25% of the plant’s magnesium is localized in the chloroplast which helps convert sunlight energy into plant energy. Magnesium uptake, like other positively charged ions, can be depressed by imbalances of cations like K+, Ca2+, and NH4+. Magnesium deficiencies can result in reduced photosynthesis, lower plant sugars and delayed maturity.
Reach out to your local Yara Agronomist to learn more about the role of specific nutrients in grapevines and how to best utilize these products in your comprehensive nutrition program.