Petiole Sampling for Determining Fertilization Needs in Cold Climate Grapes
Assessing the nutritional status of your grapevines through mature leaf petiole sampling is essential for maintaining vineyard health and productivity. Here’s how to effectively sample petioles to monitor and manage your vines’ nutritional needs.
Timing for Petiole Sampling
There are two recommended times for petiole sampling: at bloom and during veraison. Each timing has its advantages:
– Bloom Time Sampling: Preferred by some because it allows ample time to address nutrient deficiencies, particularly nitrogen and boron.
– Veraison Sampling: Others advocate for this period because nutrient concentrations are more stable, and results are more reliable.
The most critical aspect is to be consistent with your sampling time each year. This consistency enables you to compare data across growing seasons, assess the effectiveness of your fertility program, and diagnose any nutrient-related issues.
Instructions for Collecting Petiole Samples
1. Divide the Vineyard:
– Segment your vineyard into sampling areas based on soil type, cropping history, and grape variety.
– Separate samples by variety and age (e.g., separate samples for a 3-year-old Marquette block and an 8-year-old Marquette block).
– If a specific area shows symptoms of nutrient issues, collect a separate sample from that area.
2. Collect Leaves/Petioles:
– Gather 50-100 leaves/petioles. Use the higher end of the range for varieties with smaller leaves like Foch and Marquette.
– Randomly collect from 20-30 vines within each sampling unit, taking 2 leaves per vine from both sides of the rows and canopy.
– Select leaves from shoots that are well-exposed to sunlight, healthy, and free from insects, diseases, or physical injury.
3. Sampling During Different Stages:
– At Full Bloom: Collect leaves opposite the first or second flower cluster of a shoot.
– At Veraison: Collect the 5th to 7th fully mature leaves from the tip to the base of the shoot (ensure the shoot has not been pruned).
4. Preparing Samples:
– Separate the petioles from the leaf blades. If rinsing is needed, remove the leaf blades after washing. Do not soak leaves in water as it can cause nutrient leaching.
Photo credit Jean Riesterer-Loper
– Place the petioles in a labeled clean paper bag or a bag provided by the tissue analysis lab. Accurate labeling is crucial for record-keeping.
5. Drying and Shipping:
– Let the petioles dry at room temperature or send them immediately to the laboratory. Avoid using plastic bags.
6. Laboratory Coordination:
– Contact the tissue analysis laboratory before collecting and submitting your samples to understand any specific requirements they may have.
7. Nutrient Testing:
– Request testing for the following nutrients: Total nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), zinc (Zn), boron (B), iron (Fe), and copper (Cu).
By following these guidelines, you can ensure that your grapevines receive the necessary nutrients to thrive, ultimately leading to a more productive and healthier vineyard. Consistent petiole sampling is a valuable tool in your vineyard management toolkit, helping you make informed decisions year after year.
Sufficiency range for nutrients in Cold-Hardy Grape petioles (Based on Domoto and Rosen)
Nutrient | Full bloom (mid to late June) | Veraison (mid July to mid August) |
Nitrogen (%) | 1.20 – 2.20 | 0.90 – 1.30 |
Phosphorus (%) | 0.15 – 0.60 | 0.12 – 0.40 |
Potassium(%) | 1.50 – 4.00 | 1.50 – 2.50 |
Calcium (%) | 0.70 – 2.00 | 1.00 – 2.00 |
Magnesium (%) | 0.20 – 0.50 | 0.25 – 0.45 |
Sulfur (%) | > 0.12 | > 0.12 |
Manganese (ppm) | 20 – 150 | 30 – 150 |
Boron (ppm) | 25 – 50 | 25 – 50 |
Copper (ppm) | 5 – 10 | 5 – 15 |
Zinc (ppm) | 20 – 100 | 30 – 50 |
Iron (ppm) | 40 – 180 | 30 – 100 |