Petiole Sampling and Analysis in Vineyards

By Macy Lacasse and Kathryn Carter, OMAFA

Grapevine nutrient status in vines can be determined by monitoring visual symptoms, analyzing tissue samples or soil testing.

Nutrient levels should be monitored in vineyards regularly by looking for visual signs of nutrient deficiency during regular scouting, and through annual (or every two year), tissue analysis.

Monitoring for Nutrient deficiency

Scouting for symptoms of nutrient deficiency can be helpful in pinpointing areas to conduct tissue and petiole analysis. However, do not rely on visual symptoms alone for monitoring for nutrient deficiencies. Often leaf symptoms can look similar to other nutrient deficiencies, or other non-nutrient related issues (virus, trunk disease).

Soil tests prior to planting and once every three to five years after planting can provide valuable information on the availability of nutrients in the soil, and soil pH. Soil analysis can also be a useful tool in monitoring changes in the soil pH and soil organic matter that can impact nutrient supply in the soil over time. However, there can be a poor relationship between soil and vine nutrients, and in some cases nutrient levels may be high in the soils, but deficient in the vine. Differences in nutrient levels in the soils and vine can be a result of soil properties (pH, or compaction), or environmental conditions (drought, excess rain) that influence nutrient uptake. 

Tissue analysis is the best tool for assessing nutrient status in grapes as it provides insights into the nutrient status of the vine and can be used to ensure that grapevines receive the optimal levels of nutrients needed for healthy growth and fruit production. While tissue analysis can be assessed using petioles or leaf blades, petiole analysis is recommended in Ontario due to the lack of historical data on nutrient recommendations for leaf blade tissue. Integrating both soil and petiole sampling offers a comprehensive understanding of vineyard nutrient dynamics.

Timing for Petiole Sampling

Grapevine nutrient guidelines for petiole sampling have been developed for two growth stages: full bloom (50 to 80% flower caps have fallen) and veraison (initiation of fruit ripening which occurs about 70 to 100 days after bloom). Nutrient concentrations fluctuate in the vine over the growing season, therefore, sampling at specific growth stages ensures results are representative of the vine’s nutrient state during critical periods of development.

Veraison vs. Bloom

Sampling at bloom typically reflects the nutrient status before the significant energy demands of fruit set and development. This timing allows for the early detection of nutrient deficiencies, which can be corrected to support fruit set and early growth. In contrast, veraison sampling provides insight into nutrient status during the crucial period of berry ripening. Both timings offer valuable information, but they serve different purposes in managing vine nutrition throughout the growing season.

How to Conduct Petiole Sampling:

1. Selecting Representative Vines
   • Choose vines that are typical of the vineyard block in terms of growth and health
     • Avoid vines that are stressed, diseased, unusually vigorous.
     • Sample from vines that are the same age, variety and rootstock, growing on similar soil types.
2. Timing the Sample Collection
   • Bloom: collect samples when approximately 60-70% of the flowers are in full bloom. This stage provides insights into the nutrient status during early growth.
   • Veraison: collect samples at the onset of berry softening and colour change. This stage is crucial for assessing nutrient status during fruit ripening.
3. Collecting the Samples
   • Always collect petioles from the same leaf position on each vine. Typically, the petiole of the leaf opposite the first flower cluster is used at bloom (Fig.1), and the petiole of the most recently matured leaf (usually 5 to 6 leaves from the end of an actively growing shoot) is used at veraison (Fig.2).
   • Collect about 75 to 100 petioles per vineyard block.
   • If trying to diagnose a problem, take a sample from “unhealthy” vines and a separate sample from “healthy” vines for comparison.
   • Use clean paper bags (NOT plastic) to store samples. Label the bags with the vineyard block, sampling date, and growth stage.
4. Preparing Samples for Submission
   • Clean the petioles – gently rinse the petioles with distilled water to remove dust and surface residues. Do not soak them, as excessive moisture can alter the sample.
     • Dry the petioles – air dry the petioles in a shaded, well-ventilated area. Avoid direct sunlight or high heat, which can damage the tissue.
   • Packaging – place the dried petioles in labelled paper bags and send to the lab.

Figure 1 Collect petioles at bloom from leaves adjacent to flowering clusters. Figure 2 Collect petioles at veraison from most recently matured leaf (5 or 6 leaves in) on actively growing shoots.

Where to Send the Samples:

A list of OMAFRA accredited labs can be found at: Soil, leaf and petiole testing labs.

How to Interpret Petiole sample Analysis:

Interpreting the results of petiole analysis involves comparing the nutrient levels in the samples to established sufficiency ranges for grapevines in Ontario (Table 32).  When interpreting tissue analysis results, take into consideration other information such as vine growth, weather conditions, fertilizer applications and past experience.

Table 1 Nutrient Sufficiency Range of Grape Petioles

References

Dami, I. & Smith, M. (September 30, 2019). Grapevine nutrient management: petiole sampling and analysis. Ohioline. https://ohioline.osu.edu/factsheet/hyg-1438#:~:text=At%20veraison%2C%20sample%20one%20or,from%20the%20leaf%20blade%20immediately.

Fiola, J. (April 20, 2021). Tissue sampling for vineyards. University of Maryland Extension. https://extension.umd.edu/resource/tissue-sampling-vineyards/

Hickey, C., Breeden, S., MacAllister, C., Lessl, J. & Schreiner, R. P. (February 17, 2021). The fundamentals of grapevine tissue sampling for nutrient analysis. PennState Extension. https://extension.psu.edu/the-fundamentals-of-grapevine-tissue-sampling-for-nutrient-analysis

Ontario Ministry of Agriculture, Food, and Agribusiness. (July 22, 2022). Soil management, fertilizer use, crop nutrition and cover crops for fruit production. Government of Ontario. https://www.ontario.ca/page/soil-management-fertilizer-use-crop-nutrition-and-cover-crops-fruit-production#section-12

Sharma, J. & Upadhyay, K. A. (June 2012). Leaf sampling guide for grapevines. NRC for Grapes. https://nrcgrapes.icar.gov.in/Technical%20or%20Extension%20folders/LeafSamplingGuideforGrapevines.pdf

Skinkis, P. & Schreiner, P. (December 2018).  Monitoring vineyard nutrition. Oregon State University Extension. Monitoring vineyard nutrition | OSU Extension Service (oregonstate.edu)