Post-Harvest Nutrition in Vines
Now that harvest has begun and the end of another grape growing season is in sight, it’s time to take advantage of one of the grape vine’s critical phenological changes – pre-dormancy root development and nutrient storage. This is when vines “fatten up before hibernation,” drawing nutrients away from leaves, expanding roots to capture more nutrients and storing those nutrients in woody tissue. This is what supplies the energy necessary for bud-break and early shoot/root expansion next year. At this time, I prefer a post-harvest liquid fertilizer application to provide a solid nutrient foundation for next season. Key components in this application can include nitrogen, potassium, calcium and zinc depending on soil/tissue availability and harvest removal numbers.
It is very important to understand that we are mining nutrients from the soil when we pull fruit off the vine. For every ton of wine grapes harvested, we remove approximately 8 lbs of nitrogen, 3 lbs of phosphorus and 13 lbs of potassium. The plant needs to replace those nutrients, either through mining the soil with its roots or with supplemental fertilization. The Best Management Practice (BMP) nutrient budget that I use takes all inputs into consideration (soil, water, organic matter and fertilizer). Note that credits are given for soil nitrogen, water nitrogen and organic matter. The resulting deficit needs to be made up through fertilization. A vine has two peak nitrogen uptake windows – bud-break through bloom and post-harvest prior to dormancy. I would apply 80% of the vines’ N requirements in that first window and the remaining 20% post-harvest.
One of my go-to post-harvest blends is a 12-0-8 with 3% Ca, 2% Zn and 10% Humic Acid. It utilizes Nucleus 0-0-21, Axilo Ca & Zn, Hydra-Hume and Asset RS for immediate nutrient availability, rapid uptake and root stimulation. As always, consult with your local Helena Representative to determine the ideal liquid fertilizer blend necessary to address your specific situation.
- Paul W. Crout, CCA, PCA, Coastal Product Manager/Agronomist