Factors to Consider
in Selecting a
Soil Testing Laboratory
Peter Bierman, Land Resources Agent
Tom Jahns, Land Resources Agent
Soil testing is an integral part of efficient nutrient management for both farm fields and home gardens.
There are many different types of chemical tests that can be done on soil. When you send a soil sample
for analysis it is important to select the tests that will provide you with the most useful information. This
factsheet provides guidelines for selecting which chemical tests you should request and some options
for soil testing laboratories that use these procedures.
TypeS oF SoiL TeSTS on that site. The need for fertilizer is determined
Soil tests are designed to extract a portion of an through calibration experiments where different
essential plant nutrient from the soil. The results amounts of fertilizer are added to fields with dif-
of these tests can be correlated with the availabil- ferent soil test values. A crop is grown and the
ity of that nutrient for uptake by plant roots, and yield of the crop is used to develop recommen-
therefore, the need for additional amounts of the dations for how much fertilizer to apply at dif-
nutrients for good crop growth and yield. Most ferent soil test levels. This “calibration” research
soil tests are indexes of nutrient availability rath- is performed using specific soil test procedures.
er than measures of absolute amounts. Indexes Thus to effectively use the recommendations de-
tell whether nutrient availability is low, adequate veloped from the research, a soil sample must be
or high. This is more useful than knowing total analyzed using those same procedures.
amounts, because not all of a nutrient in the soil
is in a form that plants can use. In addition to the need to select the right soil
test, fertilizer recommendations are most accu-
The use of relative indexes, rather than total rate when the calibration research is done in the
amounts, means that different types of soil tests same geographical area as the soil that is being
for the same nutrient can differ numerically tested. For example, fertilizer recommendations
– even though they are all “good” soil tests. developed for a specific soil test in Washington
However, some soil tests are better adapted to may be very different than those developed us-
the characteristics of soils in different regions of ing the same soil test in Alaska. This is due to
the country. They work better on those soils than factors like the differences between soils and
alternative procedures. For this reason, it is im- climatic conditions of Alaska and Washington
portant to use the specific soil tests that are best that have an effect on plant growth. These fac-
suited for your Alaskan soil. tors result in differences in yield potential for
crops grown in different regions of the country,
After the nutrient level of a soil is determined by which leads to differences in the total amount
laboratory analysis, the next step is to develop of plant nutrients and fertilizer required for
a fertilizer recommendation for a specific crop maximum yield.
ALASkA SoiL TeST RequiRemenTS Cooperative Extension Service of one group of
The following methods are the standard soil laboratories over others not appearing on the list.
tests used by the University of Alaska Fairbanks However, soil types and growing conditions in
Agricultural and Forestry Experiment Station (AFES) Alaska are unique, so the number of soil testing
Soil and Plant Analysis Laboratory. They should be laboratories offering the exact set of tests used in
requested when using soil test laboratories outside of Alaska is very limited.
Alaska to ensure that your results will correlate with
our existing UAF fertilizer recommendations. Soil and Plant Analysis Laboratory
Agricultural & Forestry Experiment Station
University of Alaska Fairbanks
Nitrogen: nitrate (NO3-N) and ammonium (NH4-N) 533 E. Fireweed
2 Normal KCl extraction method Palmer AK 99645
Phosphorus: Mehlich-3 extraction method
SoilTest Farm Consultants
Potassium: Mehlich-3 extraction method 2925 Driggs Dr.
Soil pH: 1:1, soil:water method Moses Lake WA 98837
Lime Requirement: SMP Buffer method www.soiltestlab.com
Request test group S3. In addition to the basic Alaska
In addition to selecting the right soil tests, cost soil test requirements, you will receive results for organic
is an important factor in selecting a soil testing matter, soluble salts, sulfur, magnesium, boron, zinc,
laboratory. Laboratories offer standard packages copper, and iron.
of tests, which are usually the cheapest option if
all the tests you need are in one of the packages.
However, some packages may include a number A&L Eastern Agricultural Laboratories
of tests that you don’t really need and may be 7621 Whitepine Road
more expensive than a package from another lab- Richmond VA 23231
oratory that doesn’t include as many tests. Most 804-743-9401
laboratories also offer individual analyses for ad- www.al-labs-eastern.com
ditional tests that are not part of their standard Request soil test package MES1, along with individual
packages. This may allow you to add to the pack- analyses for ammonium-N and nitrate-N. In addition to
age to get all the necessary tests, although these the basic Alaska soil test requirements, you will receive
separate tests can have a relatively high individu- results for organic matter, magnesium, calcium, cation
al cost. Always call a laboratory for current prices exchange capacity, and percent base saturation.
and assistance in finding the least expensive way
to meet your soil testing requirements.
SoiL TeSTinG LAboRAToRieS 308 South Main St.
The following list of laboratories provides some New Knoxville OH 45871
options for meeting your soil testing needs. 419-753-2448
The list includes the UAF-AFES Soil and Plant www.blinc.com
Analysis Laboratory and three laboratories out-
side of Alaska that are certified by the National Request soil test package S001AN. In addition to the
Association of Proficiency Testing (NAPT). The basic Alaska soil test requirements, you will receive
list is not exhaustive and is only intended to results for organic matter, sulfur, magnesium, calcium,
provide some examples of suitable soil testing manganese, zinc, copper, boron, iron, cation exchange
laboratories. It is not an endorsement by the UAF capacity, and percent base saturation.
If you use one of the other laboratories, you can
list your local extension agent on the submittal
form as someone who should receive a copy of
the results. You will need to call or visit the Web
site of the laboratories outside of Alaska to obtain
a submittal form and current lab prices. Samples
for analysis must include prepayment. These
laboratories may automatically send you fertilizer
recommendations appropriate for their local con-
ditions, but it is best to have your results inter-
preted by someone who uses Alaskan research
as a basis for fertilizer recommendations.
If you decide to use a soil testing laboratory outside
A major limiting factor in selecting a suitable soil of Alaska, it is important to:
testing laboratory is that the majority of labora-
tories in the western United States do not offer 1) Request soil test procedures with proven
the Mehlich-3 extraction method. The Mehlich-3 effectiveness on Alaskan soils.
method is effective in extracting available phos- 2) Use Alaskan fertilizer recommendations to
phorus from the acidic soils found in many parts interpret the soil test results rather than rely
of Alaska, but is not suitable for the alkaline soils on fertilizer recommendations developed for
that dominate many western states. One labo- another state.
ratory in the Pacific Northwest that does offer 3) Select a laboratory that is certified by the
Mehlich-3 is SoilTest Farm Consultants in Moses National Association of Proficiency Testing
Lake, Washington. This laboratory will also au- (NAPT).
tomatically forward your soil test results to the 4) Compare the prices charged by different labo-
UAF Cooperative Extension Service so that your ratories for a similar series of tests.
district extension agent can contact you. Your dis-
trict agent can then provide UAF fertilizer recom-
mendations based on the soils in your area. The For information on how to collect a representative
UAF-AFES Soil and Plant Analysis Laboratory soil sample to submit to a laboratory for soil
continues to provide the service of sending your testing, see the uAF-CeS publication Soil
soil test results to your UAF district extension Sampling (FGV-00044).
agent for interpretation.
Visit the Cooperative Extension Service Web site at
157/12-04/PB-TJ/1000 Reprinted October 2006
The University of Alaska Fairbanks Cooperative Extension Service programs are available to all, without regard to race, color, age, sex, creed,
national origin, or disability and in accordance with all applicable federal laws. Provided in furtherance of Cooperative Extension work, acts of
May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Anthony T. Nakazawa, Director, Cooperative Extension Service,
University of Alaska Fairbanks.
The University of Alaska Fairbanks is an affirmative action/equal opportunity employer and educational institution.