Post-Harvest Nutrition in Vines
As harvest begins and the end of another grape growing season nears, it is easy to overlook one of the more critical phenological changes a grape vine makes in its growth cycle - pre-dormancy root development and nutrient storage. This is the period in which vines “fatten up before hibernation” and draw nutrients away from the leaves, expand roots to capture more nutrients and store those nutrients in woody tissue in order to supply the energy necessary for bud-break and early shoot/root expansion next year. I always reserve a post-harvest liquid fertilizer application to address this opportunity and provide a solid foundation of nutrition for next season. Key components in this fertilizer application can include nitrogen (N), potassium (K), calcium (Ca) and zinc (Zn) depending on soil/tissue availability and harvest removal numbers.
It is very important to understand we are mining nutrients from the soil when we pull fruit off the vine and haul it away. For every ton of wine grapes harvested, we remove approximately 8 lbs of N, 3 lbs of phosphorus (P) and 13 lbs of K. The plant needs to replace those nutrients through either mining the soil with its roots or supplemental fertilization. I use a nutrient budget that (N Management Planning Worksheet) takes all inputs into consideration (Soil, Water, Organic Matter and Fertilizer) as a Best Management Practice. Note that credits are given for soil N, water N and organic matter. The resulting deficit needs to be made up through fertilization. A vine has two peak N uptake windows: bud-break through bloom and post-harvest prior to dormancy. I recommend applying 80% of the vines’ N requirements in the first window and the remaining 20% post-harvest(see Nutrient Uptake Curve above).
One of my reliable 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®andAsset® RS for immediate nutrient availability, rapid uptake and root development. 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