Grapevine Nutrient Management: Petiole Sampling and Analysis

Grapevine nutrient status can be determined by three methods:  

1. Observing visual symptoms.

2. Analyzing vine tissue samples.

3. Performing soil tests.

These methods should be performed regularly by scouting visual symptoms each season, analyzing tissue samples either annually or every other year, and performing soil tests both prior to planting and once every three to five years after planting.

Of these three analyses, tissue analysis is the preferred tool for monitoring the nutrient status of your grape varieties. Tissue analysis serves two purposes: to determine the nutrient status of the vine, and identify a suspected nutrient deficiency observed in the vineyard. By directly monitoring vine nutrient status, fertilizer programs can be tailored as needed and may end up cutting grower costs.

While tissue analysis may be performed on different types of tissues (petiole and leaf blades), petiole tissue analysis (Fig. 1) is recommended for the eastern United States. This is primarily due to a lack of historical data for nutrient range recommendations of leaf blade tissue in our region.

Answers to Common Questions About Petiole Analysis

Soil vs. Tissue Testing

Soil testing is important both before planting and for established vineyards to monitor the overall balance of major nutrients and soil pH, a primary determinant of nutrient availability. However, there is a poor relationship between soil and plant nutrient levels. While a soil may be high on a specific nutrient, the same nutrient may be deficient in the vine; or the vine may show adequate levels of another nutrient while the soil test indicates a deficiency. This poor relationship may be explained by several factors related to the vine (e.g., crop levels), soil properties (e.g., soil pH, compaction), and environmental conditions (e.g., excessive rainfall, drought). For these reasons, petiole analysis is generally more useful and reliable for judging vine nutrient status than soil tests alone. However, the combination of soil and plant analysis provides the best assessment of fertility status and adjustment needs.

Timing of Petiole Sampling

Troubleshooting foliar symptoms: If you observe leaf symptoms and suspect a nutrient deficiency, collect petiole samples from vines showing leaf symptoms and from healthy asymptomatic vines. The two samples should be sent and analyzed separately for comparison purposes. This will allow you to diagnose whether the problem is related to the vine nutrient status. For troubleshooting purposes, samples should be collected anytime leaf symptoms appear during the growing season.

Routine vine nutrient assessment:

Full bloom (Fig. 2): When approximately 50 to 80% of flower caps have fallen, sample petioles from leaves that are opposite to inflorescences (flower clusters; Fig. 3). For general vine nutrient assessment, bloom time sampling is not recommended due to the frequent changes in tissue nutrient concentrations. However, bloom time sampling may be useful as a follow-up to nutrient adjustments during the previous season.

Veraison (Fig. 4): Initiation of fruit ripening, which corresponds to 70 to 100 days following bloom (mid-July to mid-August), is the ideal time for routine petiole sampling. This is due to the increased stability of nutrient concentrations relative to earlier in the season during bloom. For example, veraison sampling gives a better measure of Potassium (K) levels, which are especially critical for wine grapes since they are related to wine quality (e.g., high fruit K leads to high pH and unstable wines).

Which Vines Should I Sample?

• If you grow more than one variety, sample each variety separately.
• It is unnecessary to sample non-bearing vines (first and second year of establishment) unless you observe foliar symptoms.
• Begin tissue analysis when vines are producing (usually third year) and repeat every year until yields are stable and yearly fertilizer needs are determined.
• For mature vines, tissue analysis is done annually or every other year.

Where Do I Send My Samples?

The following is a list of labs that perform tissue analysis for a fee. Petiole analysis is usually performed for nitrogen, phosphorus, potassium, magnesium, calcium, manganese, iron, zinc, boron, and copper. Laboratory results will show the level of each nutrient and describe them as “adequate,” “deficient,” or “excessive.”

A & L Great Lakes Lab, Inc.
3505 Conestoga Drive
Fort Wayne, IN 46808
219-483-4759
algreatlakes.com

Agricultural Analytical Services
The Pennsylvania State University
University Park, PA 16802
814-863-6124
agsci.psu.edu/aasl

Brookside Farm Lab
200 White Mountain Dr.
New Bremen, OH 45869
419-977-2766
blinc.com

Dairy One
730 Warren Rd.
Ithaca, NY 14850
607-257-1272
dairyone.com

Spectrum Analytics
1087 Jamison Rd. NW
Washington Court House, OH 43160
800-321-1562
spectrumanalytic.com

What Should I Sample?

• At veraison, sample one or two petioles per vine for each variety.
• Sample petioles from mature, fully expanded leaves located five to seven leaves from the shoot tip (Fig. 5).
• Detach each petiole from the leaf blade immediately.
• Place petioles in a paper (not plastic) bag (Fig. 6).
• Label each sample and keep records of the following: varieties sampled, vineyard block where samples are collected, sampling date, and vineyard conditions.
• Prior to shipping, allow samples to dry either by oven at 200 F for 30 minutes or one day in a warm, dry, well-ventilated location.

What are Common Nutrient Deficiencies in Ohio Vineyards?

Nitrogen (N), potassium (K), and magnesium (Mg) are the most common nutrient deficiencies observed either visually or by petiole analysis. Other nutrient problems occur occasionally and include boron (B), zinc (Zn), and iron (Fe). Normal ranges for nutrient levels at full-bloom and veraison are listed in Table 1 below.

Take-home Message

Be proactive, not reactive: Do not wait until you see visual symptoms to correct a nutritional problem. If you see it, the problem already exists, and the damage has already been done on growth, yield, and fruit quality. The goal of fertilization is to prevent nutrient deficiencies and excesses from occurring in the first place.

Additional Resources

Dami et al. (2005). Midwest Grape Production Guide. Ohio State University Bulletin 919. Columbus, OH: Ohio State University. Available at
extensionpubs.osu.edu

Moyer et al. (2018). Vineyard Nutrient Management in Washington State. Washington State University Bulletin #EM11E. Available at
pubs.extension.wsu.edu/vineyard-nutrient-management-in-washington-state-replaces-pnw622-publication

Wolf, T. (2008). Wine Grape Production Guide for Eastern North America. NRAES-145.