Tissue testing time for fruit crops

by Becky Sideman, UNH Extension Professor & Specialist, Vegetable & Berry Crops

For perennial fruit crops, leaf tissue tests, which directly measure the plants’ nutrient status, are better than soil tests at determining whether your fertility management program is meeting the plants needs or not. Tissue testing is also the only way to confirm nutrient deficiencies/toxicities in problem areas in the field. Soil testing is still important for fruit growers because pH is critical for fruit crop growth. They are also critical for new plantings, where the crop has not yet been established.

Recommendations for new fruit plantings:

  • Soil test and adjust pH the year before planting
  • Soil test during planting year and fertilize according to soil test results, adjust pH if needed

Recommendations for established fruit plantings (2 years or more):

  • Soil test every 2-3 years to ensure pH is on target
  • Tissue test every 3 years to ensure that fertility program is meeting crop needs

It is almost time to take tissue tests for fruit crops (grapes, raspberries, blueberries, strawberries and tree fruits). UNH Cooperative Extension offers tissue testing plus fertil­izer recommendations for $26.00 per sample. You can get the tissue testing form here. The second page of the form provides information on how to collect good samples. You may drop off forms, checks, and samples in paper bags at your county Extension office or you can mail directly to UNHCE/Dept. of Biological Sciences in Durham.

How to take your sample:

  • Blueberries Take at least 40 leaves from 10-20 plants during first week of harvest.
  • Strawberries Take at least 40 fully expanded leaves from 10-20 plants after renovation.
  • Brambles Take at least 60 leaves from 10-20 primocanes (non-fruiting canes) in early-mid August.
  • Grapes Take 50-75 of the youngest fully-expanded leaves from 10-20 vines at bloom time OR veraison (make sure to specify your timing in the comments box on the tissue testing form). For the bloom time sampling, use the petiole from the leaf opposite the first blossom/cluster. Separate petioles (leaf stems) from leaves, and send only the petioles for analysis.
  • Tree fruits Sample 5 leaves from each of 10 trees from late July – early August. Select shoots at eye-level from around the outside of the tree (avoid water shoots or suckers). Take leaves from the mid-portion of new shoot growth.
  • Other fruits Take the youngest fully-expanded leaves during late July – early August.

Other sampling tips:

  • Sample different varieties separately. Samples should represent plants that are planted on the same soil type and are of the same age, variety and rootstock.
  • Samples should be from trees/bushes/vines that are maintained under the same cultural practices, i.e. fertilizer, irrigation and pruning practices. If you mark the sampled trees or bushes with flagging or with latex paint, you can collect leaves from the same trees/bushes each year and see the effects of your fertilization.
  • If you are using tissue tests to diagnose a problem area, make sure to send in two samples – one from a healthy area and one from the problem area.
  • Do not sample immediately after spraying or foliar feeding (these materials can affect results). Rinse leaves or petioles with water, pat dry, and place in a paper bag to dry before sending for analysis.

Once you have collected your samples, dry the leaves or petioles out, and then send them in. If you have any questions on leaf sampling or if you need additional forms, please contact your local UNHCE field specialist or call Suzanne Hebert in the Dept. of Biological Sciences at UNH at (603)862-3200.

A note about tomato: Greenhouse tomato is the only vegetable crop where tissue testing is commonly used as a way to monitor crop nutrition throughout it’s growth. This is probably because the plants and the crop have relatively high value and a long productive season. For tomato, sample the youngest fully expanded leaf from at least 8-10 plants, and follow the same methods above for analysis.

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