Sampling Instructions

students outside in a field transferring soil into a bucket

Sampling Instructions

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Plant Disease Diagnostics

Soil Nutrient Diagnostics

Plant Nutrient Diagnostics

Compost Sampling Instructions

Plant Disease Diagnostic Sampling Instructions

In order for diagnosis of your sample to be effective and accurate, please carefully follow the below shipping requirements. 

  1. Always select fresh plant material that is symptomatic but not dried out, dead, or decaying. We are unable to diagnose plants that are already dead. 
  2. Do not ship live insects or arthropods. Crushed insects and insects stuck to clear tape are unidentifiable. Place insects in freezer to kill them. Preserve soft-bodied insects in a leak-proof vial of alcohol. 
  3. Separate soil from plant material. If the root system is included, place a plastic bag around it and secure with a twist tie or rubber band to keep soil from contaminating leaves/stems.Place the entire sample into a sealed plastic bag. A dry paper towel can be wrapped around the plant to absorb excess moisture and prevent the plant from sticking to the plastic. 
  4. Never add water to the sample for shipment–water will degrade the sample and prevent an accurate diagnosis. 
  5. Ship in a crush-proof container such as a box. A box helps protect the sample and helps us provide an accurate diagnosis. Ship to the Plant Diagnostic Lab.
  6. Email us the tracking information so we know when to expect your package! 

Soil Nutrient Sampling Instructions

Follow the instructions below to obtain a representative sample. Limestone and fertilizer recommendations based on improperly collected soil samples may be inaccurate and possibly harmful to plants.  

Tools: 

  • A stainless steel soil-sampling probe, an auger, or a shovel/trowel  
  • Clean bucket 
  • Plastic bags or waterproof lined paper bags 
  • Permanent marker 

When and How to Sample: 

Samples may be collected any time of year the ground is not frozen. The waiting period for results is longest in April and May. Testing the soil in the fall is highly recommended. 

Submit a separate sample for areas differing in topography, drainage, soil texture, with different crop growth or intended crop usage, soil color, or fertilizer/amendment history. For example, a homeowner may submit one sample from a vegetable garden, one from a flower bed, and one from a front lawn. A farmer may submit a sample from each field, different crops, or from an area of low and/or high productivity. Under no circumstances should samples represent areas larger than 15 acres. Avoid sampling unusual spots such as former sites of manure or compost piles and areas where limestone or fertilizer has been spilled in previous years. The soil sample should accurately represent the entire sampling area. 

Sample Collection 

  1. Using an auger, spade, trowel, or bulb planter, collect cores or thin slices of soil from 12 or more random, evenly distributed spots (sampling points) in your sample area (see the diagram above) to the appropriate depth indicated below.  
    1. Grass – 3 to 4 inches,  
    2. Flowers, vegetables, small fruits – 6 to 8 inches 
    3. Trees and shrubs – 8 to 10 inches 
    4. Crop field: 6 to 8 inches or the plough layer depth 
  2. When using a soil probe, insert it into the soil to the proper depth (e.g., 0-6” or 0-8” for flowers, vegetables, and fruits). If a tool such as a spade is used, dig a V-shaped hole to the sampling depth; then cut a thin (approximately 1 inch thick) slice of soil from one side of the hole. For the sample, save a 1-inchwide strip of soil from the center of the spade. 
  3. Remove the soil core or the slices and place them into a clean bucket. Repeat this process at each predetermined subsampling point within your designated area. Thoroughly mix the soil to obtain one representative sample from that sampling area. Transfer at least 1 cup of this mixed soil to a plastic zippered bag. 2 cups if requesting extra tests. 
  4. Using a permanent marker, label each plastic bag with a sample ID (e.g., “front lawn,” “garden1”) that matches exactly the sample ID in your sample submission form. 
  5. Samples can be submitted in person or mailed. When mailing samples, place the sample bags and the submittal form in a sturdy box or envelope. Seal the box with packing tape and mail it to the Soil Nutrient Analysis Lab.  

Plant Nutrient Sampling Instructions

Plant tissue nutrient analysis measures the nutrient levels inside leaves or other plant parts at a specific point in time. Proper sampling is essential for accurate plant tissue analysis. The best sampling time, sample size, and plant part to collect depend on the crop. For best results, call the Soil Nutrient Analysis Laboratory at (860) 486-4274 or review the Crop-specific Sampling Guidelines below before collecting samples. 

When to sample 

In general, collect tissue samples during active growth, before plants reach senescence or severe decline. For many crops, this is mid-season, when plants are fully leafed out and still responsive to management. Some perennial crops have specific sampling windows, which are noted in the crop-specific guidelines. 

What plant parts to sample 

For most crops, collect the most recently mature leaves: the youngest leaves that are fully expanded, not the newest emerging leaves. 

  • Turfgrass: collect clippings from mowed turf, not whole plants. 
  • Grapes and some other crops: collect petioles instead of whole leaves. 

See the crop-specific guidelines on the lab’s website for crop-specific details. 

Avoid leaves that are dusty, dirty, diseased, or heavily insect-damaged unless you are specifically asked to submit symptomatic tissue. 

How many plants to sample 

Keep each sample as uniform as possible. Do not mix varieties, plant ages, or very different soil or management conditions in a single sample. 

As a general rule: 

  • For most field and vegetable crops, collect leaves from about 10 to 30 plants. 
  • For tree and small fruit crops, collect about 30 to 50 leaves. For grapes, collect about 60 petioles. 
  • For turfgrass, collect clippings from many small areas and combine them into one composite sample. 

Diagnostic samples (problem vs. normal) 

If some areas look poor and others look normal, collect one sample from the affected plants and one from healthy plants. Label each clearly as “problem” or “normal.” This side-by-side comparison makes it easier to determine whether nutrient status is contributing to the problem. 

Pairing tissue and soil samples 

Whenever possible, submit a soil sample from the same area at the same time. The soil test shows the nutrient and pH conditions around the roots, while the tissue test shows what the plant actually took up. Together, they provide a clearer picture of whether problems are related to fertility, pH, root issues, or other stresses. 

Handling, packaging, and submitting 

If leaves are dusty or soil-splashed, quickly rinse them in a mild, phosphate-free dish soap solution for less than 1 minute, then rinse in clean water. Do not soak tissues. Shake off excess water and air-dry them on clean paper towels at room temperature. 

Once dry, place the tissue in a clean paper bag or envelope. Do not seal dried tissue in plastic bags for mailing. If samples cannot be dried before shipping, deliver them the same day or ship them promptly so they do not mold or decay. 

Label each sample clearly with a unique sample ID, crop name, and plant part sampled, and complete the Plant Tissue Nutrient Analysis submission form. Send the completed form, samples, and payment to the address below. Attach a check or money order to the form. If you paid online, write the online order number on the form. 

Turnaround and notes 

  • Results are usually available in about 2 weeks. 
  • Fertilizer recommendations are not provided with tissue analysis. Tissue results should be interpreted together with soil test results and field observations. 

Further questions 

If your crop is not covered here, or if you are unsure how or when to sample, contact the Soil Nutrient Analysis Laboratory for guidance before collecting samples. 

Crop-specific sampling guidelines 

Green beans can be sampled in the summer.  Ten of the uppermost recent fully developed trifoliate leaves are needed (A trifoliate is a leaf made of three leaflets. It resembles ground clover.  

Field tomatoes should be sampled during midbloom.  Fifteen compound leaves adjacent to the inflorescences (a cluster of flowers arranged on a single stem) are required.  

Greenhouse tomatoes can also be tested.  Twenty-five mature leaves from new growth should be collected during maturity prior to fruiting.  

Peppers can be tested during flowering or fruiting.  In both cases, twenty-five mature leaves from new growth are required.  

Cabbages can be sampled throughout most of their growing season.  Fifteen whole tops can be provided from two to six weeks of age.  After two months through maturity, twelve wrapper leaves can be used.  At maturity, it is also possible to test using fifteen midribs from wrapper leaves. 

 Both Brussels sprouts and broccoli can be tested using twelve mature leaves from new growth.  The former should be collected at maturity and the latter during heading.  

Cucumbers, watermelons, and muskmelons can be tested from the appearance of flowers through harvest using twelve of the fifth leaf from the tip.  Cucumbers can also simply be tested during the summer using fifteen mature leaves from new growth.  Watermelons can also be tested during the small fruits stage using twelve mature leaves from new growth.  

Pumpkins and zucchinis can be tested using twelve mature leaves from new growth.  The former should be sampled during the summer while the latter should be sampled during maturity prior to fruiting. Squash can be sampled in the summer.  Twelve mature blades from new growth are needed.  

Turf Grass Sample Collection 

Bluegrass, tall fescue, and perennial ryegrass samples submitted for testing should consist of one to two cups of clippings collected during the summer.  

  • Plant part: Recently mowed clippings, not thatch or roots. 
  • Growth stage: Normal mowing height during active growth. Avoid sampling during extreme drought or immediately after heavy fertilization if possible. 
  • Sample size: Collect clippings from several passes of the mower in the area of interest, or hand-clip multiple small patches with clean shears. Combine into one composite sample, roughly a large handful of dried material (at least half a pint). 
  • Special notes: 
    • Keep soil, thatch, and seedheads out of the sample as much as possible. 
    • For comparison, submit separate clipping samples from poor and good areas. 

Suggested Cleaning Methods for Turfgrass Samples 

Turfgrass that has recently been sprayed with micronutrients or pesticides should not be used for testing. Washing clippings to remove soil and dust particles is recommended prior to sending the samples to the lab for analysis. If you rinse one collection of clippings and not all, the nutritional analyses may not be comparable because the concentration of some nutrients, such as K, is mobile and a portion of the K may be removed during washing. Unwashed samples may appear to have a higher concentration than washed samples, and there may be a deficiency in the washed samples when, in fact, an adequate supply of K exists. https://edis.ifas.ufl.edu/publications/EP539.   

Washing: Using a clean bucket, wash each sample separately. Fill the bucket with water that is at least 4 times the volume of the clippings. Mix clippings into the water by hand or with a mixing spoon so that debris such as fertilizer granules or sand particles are washed off of the tissue and sink to the bottom. The tissue will float. Do not wash clippings for more than 30 to 60 seconds, as some nutrients may leach out.   

Drying: Find a dry, wind-free spot. Label pieces of newspaper (or any clean dry paper) to match labels on sample containers. Remove the clippings that are floating on the surface of the water and squeeze to get rid of excess water. Spread the washed clippings into a thin layer (less than 1 inch deep) on the newspaper to air dry. Do not use an oven or microwave. Allow the clippings to dry completely (in a dry room, overnight is usually sufficient). When dry, the tissues will blow away easily so be careful in handling them to prevent cross-contamination of samples. Once the tissue has dried, they are stable and will not decay. 

Apples, apricots, and cherries can all be sampled during the summer.  Provide fifty mature leaves from new growth for testing.  

Pears and plums are also sampled during the summer.  The former requires fifty midshoot leaves from new growth (i.e., leaves in the middle of a newly developed branch), while the latter requires twenty-five whole leaves from midshoot growth.  

Peaches and nectarines require twenty-five midshoot leaves  (i.e., leaves in the middle of a newly developed branch), collected during the spring fruit set.  

Strawberries can be tested using twenty-five mature leaves from new growth collected at flowering.  

Blueberries should be sampled during the summer.  Seventy-five mature leaves from new growth should be collected. 

Raspberries can be tested two to three weeks after harvest using fifty mature leaves collected from the midsection of the primocanes. (A primocane is a first-year cane on raspberry or other bramble plants. In summer-bearing types, these canes fruit in their second year, at which point they are called floricanes.) 

Table and wine grapes are to be sampled when in bloom.  Fifty petioles from leaves opposite of the basal flower clusters should be collected. The petiole is the “stem” of a leaf.  It connects the leaf to the branch.  Wine grapes can also be sampled in the early summer using 15 whole leaves opposite from bunch clusters (i.e a fruiting body on a grape vine) . 

Currants should be sampled when the fruit is ripening.  Fifty mature leaves from new growth are needed for testing.  

Christmas Trees  

Balsam fir, concolor fir, white fir, Scots pine, and white spruce can all be tested during the summer using the needles from twenty-five 2”-3” terminal clippings.  

Greenhouse Crops  

Mums can be sampled from just prior to flower bud set through harvest.  Thirty samples of the fourth leaf from the tip would be needed.  

Poinsettias require twenty-five mature leaves from new growth, which can be collected from prior to bract coloration through flowering. 

Easter lilies should be tested using 25 mature leaves from new growth before bud expansion.  

Compost Sampling Instructions

For compost testing, the goal is to send Soil Nutrient Analysis Lab (SNAL) a sample that truly represents the whole pile. Compost can vary a lot within the same windrow or pile, so a single grab sample from one spot is rarely enough. 

Collect a representative composite sample 

Plan to build one composite sample from multiple subsamples taken from different areas and depths. 

  • Sampling locations: In most cases, collect material from at least 5 different spots around the pile or along the windrow (more if the pile is large). 
  • Sampling depths: At each location, take subsamples from three depths: 
    1. near the surface 
    2. midway into the pile 
    3. closer to the core (interior) 

If you have multiple piles or windrows, sample them separately and submit separate composite samples. 

Supplies you will need 

  • Clean auger, soil probe, or spade 
  • Clean 5-gallon plastic bucket 
  • Clean plastic tarp (helpful for mixing) 
  • Sturdy sample container (heavy zip-top freezer bag or wide-mouth plastic bottle), 1–2 quarts capacity 
  • Permanent marker for labeling 

Step-by-step 

  1. At the first location, collect about 1 pint from each of the three depths (surface, mid, core). Put all material into the clean 5-gallon bucket. 
  2. Repeat at each sampling location, adding all subsamples to the same bucket. 
  3. Mix thoroughly to make the material as uniform as possible. 
    • Mixing is often easier if you dump the contents onto a clean tarp, mix well, then return it to the bucket. 
  4. Take the composite sample from the well-mixed material. 
    • Submit about 1–2 quarts, depending on the analyses requested. 
  5. Package and label the sample clearly (sample name/ID, pile or windrow ID, date collected). 
  6. Complete the SNAL compost submission form and include any required payment information as indicated on the form. 

Drop off the sample at the lab directly or mail it promptly so the sample arrives quickly at the center. Shipping early in the week helps avoid weekend delays.