Soil Tests

Blueberries November 28, 2011 Print Friendly and PDF

Knowing the type and amount of nutrients in your soil, could save you, as a blueberry producer, money. To do this, it is important to have your soil tested.

According to the United States Department of Agriculture, nutrient management is important part of growing blueberries. Testing your soil for nutrients and pH is important to provide your plants with the proper balance of nutrients while avoiding over-application. The cost of soil testing is minor in comparison to the cost of plant materials and labor. Correcting a problem before planting is much simpler and cheaper than afterwards.

Kenny Bailey of the North Carolina State University Cooperative Extension service says plants require 16 essential nutrients to grow. In the publication, Importance and Step by Step Instructions for Taking a Soil Test for Homeowners,Bailey states nitrogen, phosphorous and potassium are major elements and are required in relatively large amounts. Other nutrients, such as calcium, sulfur and magnesium are minor elements and are required in moderate amounts. Still other nutrients are required in extremely small amounts, and are still just as important as the major nutrients. If any of the 16 essential elements are not present in adequate amounts, plant growth and development will decrease. On the other hand, if some of the same nutrients are present at excessive levels, they can be toxic to plants and be a source of pollution in the environment.

To make sure your soil has an adequate amount of nutrients, collect soil samples and have them tested. The best time to collect samples is before spring fertilization or after harvest from uniform sampling areas with similar management. Use a soil tube, soil auger or a spade to take samples. Sample to the plow or rooting depth (usually 6 inches to 12 inches deep). Each sample should represent a uniform area. Size up the area and observe these variations:

  • Differences in texture (sand, silt, clay),
  • Color,
  • Slope,
  • Degree of erosion,
  • Drainage, and
  • Past management (fertilization, manure application, rotation, irrigation type, and so on).

Julie Treat, Arkansas Cooperative Extension Service horticulturist, shows the proper method for collecting a soil sample to send in to your local Cooperative Extension Service office in Collecting a Soil Sample (Video).

 

Obtaining Soil Samples

Here's how the USDA recommends obtaining soil samples:

  • Take 15 to 20 subsamples in zig-zag form shown from each uniform area. Mix thoroughly in a plastic container and fill a plastic bag with a pint of soil. This is the composite sample, which represents the field or area. Label each container with your name and address and the field or sample identification (ID) corresponding to the ID on the information sheet.
  • Avoid (or sample separately, if of interest) such areas as:
    • Dead or back furrows,
    • Manure piles,
    • Old straw piles,
    • Waterways,
    • Terraces,
    • Fencerows, and
    • Unusual or difficult spots.
  • Repeat the sampling procedure outlined on each uniform area you want tested.
  • Air-dry the samples before mailing.
    • Do not use heat for drying.
    • Wet samples will delay analyses up to one week.

Where to Send Soil Samples

According to the Natural Resources Conservation Service Conservation Practice Standard Code 590, soil test analyses should be performed by:

  • Laboratories successfully meeting the requirements and performance standards of the North American Proficiency Testing

Program (NAPT) under the auspices of the Soil Science Society of America, or

  • State recognized programs that consider laboratory performance and proficiency to assure accuracy of soil test results.

For blueberry producers growing traditional crops, a list of laboratores is available from the American Horticultural Society. For producers growing organic crops, a list of laboratories is available from the National Sustainable Agriculture Information Service -- ATTRA.

Soil and tissue testing shall include analyses for any nutrients for which specific information is needed to develop a specific nutrient plan. Request analyses necessary for monitoring or amending the annual nutrient budget, for example, pH, electrical conductivity (EC), soil organic matter, nitrogen, phosphorus and potassium.

Growers also can contact their local Cooperative Extension Service office for information about soil testing labs.

Costs

Depending on which tests are needed, a soil test is relatively inexpensive. A private laboratory can provide pH, macro and secondary nutrient levels and a fertilizer recommendation for between $7 and $10, according to Natural Resources Conservation Services. Home soil testing kits, which cost from a few dollars to several hundred dollars, are available at stores and on the Internet. Although most home soil test kits are inexpensive, they provide only provide a generalization of nutrient levels.

After Test Results are In

Soil tests are not complicated to read, but you should know what to expect when the test results are in. Washington State University Cooperative Extension Service has some tips for homeowners to follow when reading soil test results. These are:

  • Be sure you understand what units of measure, parts per million (ppm) or pound per acre, the soil lab you choose uses.
  • Results from soil tests do not always translate easily into actions to take. Ask your soil testing lab if they offer advice or interpretation of the results.
  • Be careful with home soil testing kits. Often these kits are not very sophisticated and may only offer information on relative levels of nutrients or acidity. The chemicals in home tests have a limited life span and have the potential to be inactive by the time you use them.

Be sure to follow the recommendations you get to correct any inadequacies, eliminate hardpans, improve soil structure and adjust organic matter to acceptable levels for your particular blueberry bushes.Blueberry plants will perform poorly in areas with large amounts of wood ash. This may occur in sights where windrows, rows of vegetative debris, were recently burned on newly cleared land. These areas have high concentrations of minerals, salts and a high pH level. The location of these windrows should be considered when laying out the field to reduce problem areas after planting.


Once your crop is established, continue to take periodic soil samples. The USDA says people could save as much as $100 per acre by spending a few dollars on soil tests.

Reference:

Baily, Kenny. Importance and Step by Step Instructions for Taking a Soil Test for Homeowners. Retrieved 19 May 2010.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.