If you suspect a nutrient deficiency:

  1. Sample when the symptom first appears (see or Plant Deficiency Symptoms section).
  2. In the same field or area, collect similar samples of plant materials from plants that appear abnormal.
  3. Make sure that the symptoms are not due to a factor unrelated to plant nutrition. The parts of plants to sample depend on the plant and its growth stage. See are plant sampling techniques section below for a list of the best parts to sample for common crops. More specific sampling strategies may be necessary for cotton and peppers (chili). Also, many devices are available for a "quick test" of the plant nitrogen status.

Instructions for petiole or leaf sampling may differ. Also, comparing samples from both a "good" and a "bad" area often helps in determining corrective action. If specific sampling guidelines are not given here, collect recently mature leaves just below the growing point from at least 10 plants.

When gathering the tissue sample in the field, use a clean container. A plastic pail or a paper bag works best. Never use a metal container because it can contaminate the sample.

If the plant samples have soil, fertilizer, dust, or spray residues on them, they will need to be cleaned. A dry brush works best, but for stubborn residues, wipe the samples with a damp cloth or wash them with distilled or deionized water. However, do not prolong the washing because it can leach nutrients out of the tissue.

Air-dry the samples in the shade, not in the sun. To prevent contamination, place the dried samples into clean paper bags or envelops for mailing to the laboratory. Never place fresh plant tissue samples in plastic bags for mailing. The plastic bags do not allow the samples to dry, so they may decompose. It is also a good idea to take a soil sample in the same vicinity as the plant sample because the soil test may help to interpret the plant tissue analysis readings. Mail the samples to: Capco Analytical Services, Inc. 1536 Eastman Ave. Suite B, Ventura, CA, 93003

Information to Provide with the Sample and the Chain of Custody

When you mail the samples to the lab, please be sure to provide the following information on the chain of custody:

  • Type of crop
  • Variety
  • Soil type (if known)
  • Current crop fertilization and management practices (such as stand, kinds and rates of fertilizer, method of fertilizer application)
  • Last year’s crop fertilization practices and yield
  • Irrigation frequency and quality of irrigation water
  • Visual appearance of crop
  • Insect and disease problems (if any)

This information is necessary for sound interpretation of the plant tissue analysis.

Things to Avoid When Collecting Your Plant Sample

Do not sample the following:

  • Young, emerging leaves; old, mature leaves; and seeds. These plant parts usually are not suitable because they are not likely to reflect the nutrient status of the whole plant
  • Diseased or dead plants
  • Plants that have insect or mechanical damage

A single plant showing visual deficiency symptoms, unless it is possible to sample normal plants from an adjacent area in the field. Normal plants give a reference to help interpret the chemical analysis of the deficient plant sample.

Tissue Sampling Techniques for Specific Plants

Crop When to Sample Where to Sample Number to Sample
Alfalfa Early bloom  Top 6 inches or upper third of plant 12-30
Apples, pears, almonds, apricots, cherries, prunes, plums Midseason (June-July) Leaves from current season’s nonfruiting, nonexpanding spurs 50-100
Asparagus Maturity Fern, 18-30 inches above ground line 10-30 
Beans Seedling stage or All above-ground portions 20-30 
Before or at bloom Recently mature leaf  20-30 
Broccoli Before heading Recently mature leaf  12-20
Brussels sprouts Midseason  Recently mature leaf  12-20
Canola Before seed set  Recently mature leaf  60-70 
Carnations Newly planted  4th to 5th leaf pair from base 20-30
Established th to 6th leaf pair from base  20-30
Celery Midseason  Outer petiole of recently mature leaf  12-20
Chrysanthemums Before or at bloom Top leaves on flowering stem  20-30
Clover Before bloom  Upper 1/3 of plant  30-40
Corn/sweet corn Seedling stage or  All above-ground portions 15-20
Before tasseling or  First fully developed leaf from the top of the plant all above-ground portions  15-20
Tasseling to silking  First fully developed leaf from the top of the plant  Leaf opposite and below ear 12-20
Cotton Full bloom Recently mature leaf from main stem  40-50 
Cucumbers Before fruit set Recently mature leaf  12-20
Grapes At bloom Petioles or leaves adjacent to basal clusters at bloom 50-100
Grasses/forage mixes Stage of best quality (before seed emerges)  Upper 4 leaves  30-40 
Head crops (cabbage, cauliflower) Before heading  Recently mature leaf at center of whorl  12-20
Leaf crops (such as lettuce, spinach) Midseason  Recently mature leaf  12-20
Melons Before fruit set  Recently mature leaf  12-20
Ornamental trees and shrubs Current year’s growth Recently mature leaf  30-70
Peaches and nectarines Midseason (June-July) Midshoot leaflets/leaves  25-100
Peanuts Before or at bloom  Recently mature leaves 40-50 
Peas Before or at bloom Leaves from 3rd node from top 40-60
Pecans Midseason Midshoot leaflets/leaves  25-60
Peppers Midseason  Recently mature leaf  25-50
Pistachios Mid- to late season (August) Terminal leaflets from non-fruiting shoots  25-60
Poinsettias Before or at bloom  Recently mature leaf  15-20
Potatoes Before or at bloom  3rd to 6th leaf from growing tip 25-30
Raspberries Midseason  Recently mature leaves from laterals of primocanes 30-50
Root/bulb crops (such as carrots, beets, onions) Midseason before root or bulb enlargement Recently mature leaf  20-30
Roses At bloom Recently mature compound leaf on flowering stem  25-30
Small grains (barley, oats, wheat, rye, rice) Seedling stage   All above-ground portions  25-40
Before heading 4 uppermost leaf blades  25-40
Sorghum (milo) Before or at heading 2nd leaf from top of plant  20-30
Soybeans Before or at bloom Recently mature, trifoliate leaves from the top of the plant 20-30 
Strawberries Midseason Recently mature leaves  25-40
Sugar beets Midseason  Recently mature leaf at center of whorl  25-30 
Sunflowers Before heading  Before heading  20-30 
Recently mature leaf Recently mature leaf 20-30 
Sweet potatoes Midseason or 3rd to 6th leaf from tip center  20-30
Before root enlargement  Mature leaves  25-35
Tomatoes (field) Midbloom  3rd to 4th leaf from growing tip 15-20
Tomatoes (trellis or indeterminate) Midbloom from 1st to 6th cluster stage  Petiole of leaf below or opposite top cluster  12-20
Turf Active growth  Leaf blades. Avoid soil contamination.  2 cups
Walnuts June-July Terminal leaflets/leaves from non-fruiting shoots  25-40