Tree Fruit Soils and Nutrition











 

Leaf Sampling

Sampling Procedure (from Temperate Zone Pomology book, see references)

  1. Samples should only be collected from plantings old enough to bear a commercial crop or where a nutritional problem is suspected.

  2. Collect leaf samples during mid-July through August.

  3. A single sample should not represent an area larger than 2 hectares (about 5 acres).

  4. Include only one cultivar or strain in a sample and preferably only one rootstock type.

  5. Mark or map each plant or area sampled for future resampling.

  6. Select leaves from the periphery of trees at shoulder height or higher from the middle of the current season's terminal shoots of about average vigor.

  7. Collect 10 leaves per tree from shoots randomly selected from all sides of the tree. Select leaves free of disease or damage (unless diagnosing a trouble spot).

  8. 50 leaves per sample are sufficient unless leaves are small. 

  9. Remove leaves with the petiole (use a downward pull).

  10. For trouble spots, take a composite sample from five affected trees and five non-affected trees and label bags accordingly. 

  11. Contaminated samples (by soil, spray, or other residues that would interfere with analysis) should be cleaned with a nonionic detergent solution and rinsed with soft water (not tap water). Wash leaves ASAP and quickly (for one minute or less), 

  12. Dry leaves at 80oC or air dry. Samples should not be stored in a location that is moist where mold or damage may occur.

  13. Submit the dried sample to laboratory for analysis along with the following information: orchard name and location, date of sampling, soil type, cultivar, fertilizer practice, and special problems. Make sure the samples are labeled in a fashion that the corresponding location in orchard can be found easily.

Timing

Leaf nutrient levels change over the season.  The recommended sampling times represent a compromise between the best sampling times for various mineral elements.  Nutrient concentrations increase during the season up to about harvest.  After harvest levels of mineral elements in leaves decline.  After 1 September, the rate of decline increases and leaf analyses can no longer be a reliable indicator of nutrient status. Early in the season, growth is rapid and levels of some elements may be high and/or increasing. The most stable time for sampling therefore, has been set to be between the end of shoot growth and the start of migration from the leaves to the shoots (typically during mid-July through August).

 

Crop loads

Heavy crop loads can lead a dilution of mineral content found in the leaves.  Light crop loads tend to be associated with low N and high K.

 

 

 

 

 

Updated November 24, 2004

 

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