Soil test may refer to one or more of a wide variety of soil analyses
conducted for one of several possible reasons. Possibly the most
widely conducted soil tests are those done to estimate the
plant-available concentrations of plant nutrients, in order to
determine fertilizer recommendations in agriculture. Other soil tests
may be done for engineering (geotechnical), geochemical or ecological
1 Plant nutrition
1.1 Storage, handling, and moving
3 See also
5 External links
In agriculture, a soil test commonly refers to the analysis of a soil
sample to determine nutrient content, composition, and other
characteristics such as the acidity or pH level. A soil test can
determine fertility, or the expected growth potential of the soil
which indicates nutrient deficiencies, potential toxicities from
excessive fertility and inhibitions from the presence of non-essential
trace minerals. The test is used to mimic the function of roots to
assimilate minerals. The expected rate of growth is modeled by the Law
of the Maximum.
Labs, such as those at
Iowa State and Colorado State University,
recommend that a soil test contains 10-20 sample points for every 40
acres (160,000 m2) of field.
Tap water or chemicals can change
the composition of the soil, and may need to be tested separately. As
soil nutrients vary with depth and soil components change with time,
the depth and timing of a sample may also affect results.
Composite sampling can be performed by combining soil from several
locations prior to analysis. This is a common procedure, but should be
used judiciously to avoid skewing results. This procedure must be done
so that government sampling requirements are met. A reference map
should be created to record the location and quantity of field samples
in order to properly interpret test results.
Storage, handling, and moving
Soil chemistry changes over time, as biological and chemical processes
break down or combine compounds over time. These processes change once
the soil is removed from its natural ecosystem (flora and fauna that
penetrate the sampled area) and environment (temperature, moisture,
and solar light/radiation cycles). As a result, the chemical
composition analysis accuracy can be improved if the soil is analysed
soon after its extraction — usually within a relative time period of
24 hours. The chemical changes in the soil can be slowed during
storage and transportation by freezing it. Air drying can also
preserve the soil sample for many months.
Soil testing is often performed by commercial labs that offer a
variety of tests, targeting groups of compounds and minerals. The
advantages associated with local lab is that they are familiar with
the chemistry of the soil in the area where the sample was taken. This
enables technicians to recommend the tests that are most likely to
reveal useful information.
Soil testing in progress
Laboratory tests often check for plant nutrients in three categories:
Major nutrients: nitrogen (N), phosphorus (P), and potassium (K)
Secondary nutrients: sulfur, calcium, magnesium
Minor nutrients: iron, manganese, copper, zinc, boron, molybdenum,
The amount of plant available soil phosphorus is most often measured
with a chemical extraction method, and different countries have
different standard methods. Just in Europe, more than 10 different
soil P tests are currently in use and the results from these tests are
not directly comparable with each other.
Do-it-yourself kits usually only test for the three "major nutrients",
and for soil acidity or pH level.
Do-it-yourself kits are often sold
at farming cooperatives, university labs, private labs, and some
hardware and gardening stores. Electrical meters that measure pH,
water content, and sometimes nutrient content of the soil are also
available at many hardware stores.
Laboratory tests are more accurate
than tests with do-it-yourself kits and electrical meters. Here is an
example soil sample report from one laboratory.
Soil testing is used to facilitate fertilizer composition and dosage
selection for land employed in both agricultural and horticultural
Prepaid mail-in kits for soil and ground water testing are available
to facilitate the packaging and delivery of samples to a laboratory.
Similarly, in 2004, laboratories began providing fertilizer
recommendations along with the soil composition report.
Lab tests are more accurate, though both types are useful. In
addition, lab tests frequently include professional interpretation of
results and recommendations. Always refer to all proviso statements
included in a lab report as they may outline any anomalies,
exceptions, and shortcomings in the sampling and/or analytical
Some laboratories analyze for all 13 mineral nutrients and a dozen
non-essential, potentially toxic minerals utilizing the "universal
soil extractant" (ammonium bicarbonate DTPA).
Common mineral soil contaminants include arsenic, barium, cadmium,
copper, mercury, lead, and zinc.
Lead is a particularly dangerous soil component. The following table
University of Minnesota
University of Minnesota categorizes typical soil
concentration levels and their associated health risks.
Children and pregnant women should avoid contact with soil estimated
total lead levels above 300 ppm
Extracted lead (ppm)
Estimated total lead (ppm)
Six gardening practices to reduce the lead risk
Locate gardens away from old painted structures and heavily traveled
Give planting preferences to fruiting crops (tomatoes, squash, peas,
sunflowers, corn, etc.)
Incorporate organic materials such as finished compost, humus, and
Lime soil as recommended by soil test (pH 6.5 minimizes lead
Discard old and outer leaves before eating leafy vegetables; peel root
crops; wash all produce
Keep dust to a minimum by maintaining a mulched and/or moist soil
Plant tissue test
Soil Science - Malcolm E. Sumner - Google Books. Books.google.com.
^ Jordan-Meille, L.; Rubæk, G. H.; Ehlert, P. a. I.; Genot, V.;
Hofman, G.; Goulding, K.; Recknagel, J.; Provolo, G.; Barraclough, P.
(2012-12-01). "An overview of fertilizer-P recommendations in Europe:
soil testing, calibration and fertilizer recommendations".
and Management. 28 (4): 419–435.
doi:10.1111/j.1475-2743.2012.00453.x. ISSN 1475-2743.
^ "wlabs.com". wlabs.com. Retrieved 2012-11-08.
^ Carl J. Rosen. "
Lead in the Home Garden and Urban
Extension.umn.edu. Retrieved 2012-11-08.
Colorado State University
Colorado State University Extension Service
Mail-in soil test kits and nutrient management/fertilizer reports
Field Book for Describing and Sampling Soils
Topics in soil science
Environmental soil science
Agricultural soil science
Soil retrogression and degradation
Soil compaction (agriculture)
Pore space in soil
Pore water pressure
Soil organic matter
Soil water (retention)
USDA soil taxonomy
World Reference Base
Soil Resources (1998–)
FAO soil classification (1974–98)
Soil Classification System
Soil Classification System
Référentiel pédologique (French classification system)
Canadian system of soil classification
1938 USDA soil taxonomy
List of U.S. state soils
List of vineyard soil types
Types of soil
Soil guideline value
Soil salinity control
Soil policy (Victoria, Australia)
Canadian Society of
International Union of
Soil and Water Conservation Society
National Society of Consulting
Soil Science Society of America
National Society of Consulting
Australian Society of
Soil Science Incorporated
International Year of Soil
World Congress of
Impervious surface/Surface runoff
Category soil science
Index of soil-related articles