Since bloom was accelerated by the recent warm days, most of you will have already collected and submitted your bloom time tissue samples to monitor vine nutrient status. Many growers are making the switch to using leaf blades rather than petioles based on my recommendations. While this may seem a little unnerving for some, using leaf blades for nutrient tests has the following advantages:
- outperform petioles in predicting vine responses to nitrogen, phosphorus and potassium
- have a larger dynamic range and lower variance for most nutrients than petioles
- values from leaf blades can diagnose some nutrient deficiencies better than values from petioles
- leaf blades are the logical choice since the blade is metabolic ‘work-horse’ of the canopy.
For those of you who are concerned about making the switch to leaf blades because all of your past records are based on petiole values, consider sending in both leaf blade and petiole samples for 1 or 2 years in some blocks to help make this transition. Petioles have a few advantages as well:
- smaller size reduces contamination from dust or chemicals
- require more leaves to be sampled from a given block which should decrease sampling error have been the basis of the U.S. grapevine nutrient tests
Whether you use leaf blades or petioles for your vine nutrient analyses is your choice. My lab will continue to monitor both tissues in our research to provide information for both types of tissue analyses.
Research has also shown that sampling at veraison instead of bloom can provide a better indication of vine nutrient status for routine monitoring. Nutrient concentrations in leaves and petioles are less stable near bloom-time because of greater fluctuations in weather conditions and rapid shoot growth at this time of year.
Guidelines for interpreting your nutrient analyses are available here with information explaining how the guidelines were derived. The quantities of nutrients required by Pinot noir and the time of the season when nutrient uptake from soil occurs is also summarized in this document. Keep in mind that nutrient guidelines should not be considered absolute values that you must obtain or avoid in your vineyard blocks. Tissue nutrient guidelines cannot be rigidly defined and followed in practice because many factors influence nutrient status, including rootstocks and scions, soil type, recent weather conditions, and recent inputs or practices (fertilizer, tillage, sprays, irrigation, etc.). However, nutrient test results from the same vineyard blocks over years can provide a useful gauge of vine nutritional health and indicate when action should be taken to meet your production goals.
Here are some additional key points to remember about grapevine nutrient tests:
- Keep records from the same blocks over years. Examining trends over years is really your primary goal in routine nutrition testing. This is far more valuable than single season results and some testing labs are now providing the past few years of data with your current season test results. Once you have experience with certain blocks, you can consider skipping every other year to save money.
- Be consistent in the way you sample your vineyard blocks (follow the same pattern each year or designate and flag certain rows to revisit each year).
- Avoid sampling from problem areas within a block and avoid leaves with any damage.
- Sample within 1 to 3 days of bloom or veraison every year.
- Collect samples in paper bags and submit them to the lab the same day.