Like most perennial plants, the nutritional requirements of grapevines are best evaluated through a combination of soil testing, tissue analysis, observations, and past experience. Soil tests can give growers information about soil pH and basic nutrient levels in the vineyard. To ensure that your grapevines are taking up sufficient nutrients, careful observation of the foliage and periodic testing for the mineral content is essential. Here is some basic information on soil and plant tissue testing in vineyards offered by the University of Georgia Agricultural and Environmental Services Laboratory (aesl.ces.uga.edu).
Soil Analysis
Areas to sample: The first step is to determine the areas in your vineyard that will be represented by each sample. Look for differences in soil color, texture, drainage, slope, past management history, or growth of vegetation in the area. It may be helpful to use a soil map. You can draw your own or generate one using this website: websoilsurvey.sc.egov.usda.gov. Generally, a single soil sample should not represent an area over 5 acres. Collect soil samples using a soil probe, spade, or auger, randomly collecting 10-20 subsamples within each previously defined area.
Pre-plant: Sample the top 16 inches of soil, separating the top 0-8 inches from the bottom 8-16 inches into two discrete samples. While grape roots in many soils will penetrate beyond 16 inches, it is not practical to effectively incorporate desired materials (lime/fertilizer) below this depth, so assessing the top 16 inches is sufficient.
Post-plant: Collect soil samples from the upper 8 inches of soil, staying under the plant canopy.
Collect samples in the Fall/Winter when the plants are dormant and the soil is slightly damp (not dry or saturated). Avoid taking samples 6-8 weeks after applying fertilizer or lime. Mix the subsamples together and fill a soil bag (about 2 cups) to take to your local county extension office (Locate your office: https://extension.uga.edu/about/county/index.cfm)
Soil Test Descriptions & Fees
Routine Soil Analysis
Standard fertility test: $6.00 + shipping
The report will includes pH, lime buffering capacity, Mehlich I extractable nutrients (P, K, Ca, Mg, Mn, Zn) and recommendations for nutrient and pH adjustment.
Additional soil tests can be viewed here: Fee Schedule
Plant Tissue Analysis
Plant tissue analysis for grapevines, which involves testing the petioles or leaf blades, is the preferred method of monitoring the nutritional health of vineyards. Tissue analysis may be done for two reasons: the first is troubleshooting to confirm or deny a suspected nutrient problem within the grapevines, and the second is to monitor nutrient levels within the vines to detect a nutritional problem before it negatively impacts yield and fruit quality.
What to sample and how much
Analysis of petioles (~60-100 petioles) or leaf blades (~20-40 leaves) will give a reasonable estimation of nutrient status. However, petiole analysis best indicates the current movement of nutrients towards the leaf blade (nitrogen, phosphorous, potassium, and magnesium).
Site Selection
Samples should be taken from a single management area and should represent one single variety/rootstock that is maintained under the same cultural practices (i.e., fertilization, irrigation, and pruning). Generally, a tissues sample should not represent an area over 10 acres.
When to Sample:
Suspected Nutrient Problem: When troubleshooting nutrient deficiencies, collect petioles or leaf blades any time during the season from symptomatic leaves regardless of their shoot position.
Bloom: When ⅔ of the flower caps have been shed, collect petioles from leaves located opposite the first or second flower cluster from the bottom of the shoot. Bloom time is especially important because insufficient levels of micronutrients can have a season-long effect on fruit quality.
Véraison: Collect petioles from the youngest fully expanded (mature) leaves on the shoot, usually located from five to seven leaves back from the shoot tip. Sampling at veraison may provide a more accurate assessment of the status of other elements. Due to the timing, adjustments to be made to the fertility program will be applicable to the next growing season.
Handling Samples
Place in a clean paper bag and label with appropriate information so that when you receive the report, you can easily identify the variety, location, growth stage, and date. The samples should be taken to your local county extension office as soon as possible.
Plant Test Descriptions & Fees
Standard Plant Tissue: $25.00 + shipping
The report includes N, P, K, Ca, Mg, S, Mn, Fe, Al, B, Co, Zn, and Ni along with sufficiency ranges for nutrients.
For additional information or questions, contact:
Jay Lessl
jlessl@uga.edu
706-542-5350
