Optimize Nutritional Applications in Your Vineyard by Applying Agro-K’s 5Rs
Growing grapes – like any crop—requires careful management of resources such as labor and crop inputs. Applying the Right nutrients at the Right time, in the Right form, in the Right mix, to the Right place in the plant (Agro-K’s 5Rs of crop nutrition) maximizes the beneficial impacts of these crop inputs while optimizing expenses such as labor. There are multiple times during the growing season where applying nutrients can have beneficial effects on yield and crop quality. Applying the principles behind Agro-K’s 5Rs, when are the key points of development for your crop and what should be applied to really optimize those nutritional dollars?
Sean Jacobs, Senior Agronomist for Agro-K, says if he had to pick a few key windows of opportunity where applying the right nutrients makes the largest impact on the crop of grapes, they would be bud differentiation (7 to 14 days post-bloom), berry set, and veraison.
Early Calcium is Key
Getting calcium into the plants early in the season is essential for maximizing both leaf and fruit size. Plant (leaf, fruit, and structural) growth occurs in two phases, cell division and cell expansion. In these phases, the potential number of cells that can be created during cell division and the limit of how large those cells can expand later are both dependent on the concentration of available calcium as new cells are created. Calcium is the first “choke-point” in the long journey to larger, more durable fruit.
As fruit development progresses, cell division ends, and cell expansion begins. “Cells will get bigger, but there will not be significantly more cells created,” Jacobs says. “It’s like a balloon; once the balloon is made, the amount of latex in it is fixed. That amount of latex dictates the balloon’s maximum size. You can only blow it up to the limits of the amount of latex it contains.”
Jacobs recommends Agro-K’s Vigor-Cal-Bor-Moly™, which is formulated to provide calcium, boron, and molybdenum. During fruit cell division molybdenum and boron act synergistically to enhance calcium uptake and assimilation. Calcium thickens cell walls, providing strength and structure to the fruit cells, ultimately helping with berry quality and shelf life. Vigor-Cal-Bor-Moly applications can start as early as pre-bloom.
Bud differentiation — seven to 14 days post-bloom — is a key window of opportunity for other nutrients as well, Jacobs explains. It’s already time to plan for the following year’s crop, even though this year’s crop hasn’t developed yet. The flower and leaf buds for the next season are simultaneously forming during this period and having the right environmental conditions and right nutrients in place will influence how many flower buds develop.
“While these buds are forming you want to provide the right micronutrients to encourage healthy bud formation in support of next year’s crop,” Jacobs says. “The shoots and leaves are still expanding, the current fruit is developing, and next year’s buds are forming, so there are many processes going on within the plant at the same time.”
Along with the Vigor-Cal-Bor-Moly, Jacobs recommends Micro SeaMix, which provides key micronutrients needed by the plant at this point. Agro-K’s Micro SeaMix contains manganese, magnesium, copper, zinc, molybdenum, and the seaweed species Ascophyllum nodosum. The seaweed helps with nutrient absorption, rachis elongation, and stress mitigation. Magnesium Dextro-Lac® provides an extra shot of magnesium, which is a vital element in chlorophyll. Extra magnesium helps keep leaves resistant to sun damage and aging, so they are productive for a longer time, Jacobs says. Lastly, nitrogen, phosphorus, and potassium – the big three – can’t be forgotten but getting the right nutrient ratios is critical, making AgroBest® 9-24-3 ideal during this window of opportunity.
Setting the Size
Additional applications of Vigor-Cal-Bor-Moly and AgroBest 9-24-3 are also important at berry set and development to support cell division, cell wall structure and metabolic processes, Jacobs says. Rachis development, which is accelerating now, can affect fruit quality. If the rachis is too short, berries will become packed together limiting their size and the amount of air circulation within each cluster, increasing disease pressure.
“Cell division is important in the developing fruit and is also important in the growth of the rachis,” Jacobs says. “A seaweed product such as Symspray, which is nutrient-enhanced Ascophyllum nodosum, helps with calcium uptake and rachis elongation, spacing out the berries.”
Sweetening the Fruit
Veraison, which is when the berries begin the ripening process, is another window of opportunity, Jacobs says. Once the grapes are at about 16 Brix the crop is at an inflection point; enough acids have accumulated within the berry that they begin to be metabolized, releasing hydrogen protons. Hydrogen protons flow out of the berries, allowing sugars to go in — even against ever more concentrated gradients of sugar. Sugar doesn’t do this by itself. Potassium becomes the key element here. Normally, soluble solids such as sugars move naturally from higher concentrations to areas of lower concentration. But a special type of pump—a symporter—exchanges hydrogen inside the berry for potassium outside the berry. This exchange drives a pump powerful enough to move sugars against a concentration gradient that by the end of ripening is substantially more concentrated within the berry than without.
“KDL/Potassium Finishing Solution 0-0-24 provides the potassium needed in the right formulation for easy absorption,” Jacobs says. “KDL stands for potassium dextro-lac and is a sugar complex. It is rapidly absorbed and used by the plant and does not require much energy for assimilation. Agro-K’s Micro SeaMix also has a role to play during this window of opportunity. It supports the photosynthetic machinery operating at maximum capacity despite increased oxidative and heat stresses experienced as the season progresses from ripening to harvest.”
Jacobs acknowledges that there are other time periods where foliar nutrient applications would be beneficial. Certain fields may need more than others. But focusing on these three time periods are good first steps towards optimizing the return on your investment.