pH is an indication of the relative acidity or
alkalinity of the soil. It is based on a logarithmic
scale from 0 to 14, with 7 being neutral. Being a
logarithmic scale each change of 1.0 unit is a 10x
unit change. For example a soil pH of 6.0 is 10
times more acid that a pH of 7.0. A soil pH of 5.0
is 100 times (10x10) as acid as a pH of 7.0. Most
plants perform best and a wider range of nutrients
are adequately available with a soil pH between 6.0
and 7.0. However, some plants require more acid
soils. Few, if any do better with soil pH higher
than 7.0. For more information on
soil pH click here.
This is a test that is conducted to determine the
amount of lime to apply in order to reach the
desired soil pH. It does not represent the intended
or target pH for that crop or plant. This test is
required due to the effect of the soil CEC. For more
buffer pH click here.
All are reported with a status assignment (Low,
Medium, Good, High, and Very
High). The standard agricultural report has
the first letter of each status printed with the
result, while the other reports use the bar graphs
to indicate the status.
Reported in pounds per acre or parts per million
(ppm x 2 = lb./A), depending on the report. These
status ranges may be unique for specific crops or
Potassium (K), Magnesium (Mg), Calcium (Ca)
These are the three major cation elements and are
reported in the same format. The amount contained in
the sample is reported in either pounds per acre or
parts per million (ppm), depending on the report
format. These status ranges may be unique for
specific crops or plants. Additional information is
reported as the percent saturation of each element.
Percent saturation is best described as the percent
of the CEC that is occupied by the element. The
desirability of a particular
percent saturation for each of these nutrients
is sometimes affected by other soil conditions and
the plant species to be grown. For more information
magnesium click on the individual element.
Sulfur (S), Boron (B), Zinc (Zn), Manganese
(Mn), Copper (Cu), and Iron (Fe)
Each element is reported in parts per million
(ppm). The reported Cu and Mn recommendations are
derived by a proprietary formula that calculates the
effects other soil factors on the availability of Cu
and Mn. For more information on
iron click on the individual element.
This is the Bray P2 phosphorus test.
It is a test developed many years ago to monitor the
effects of large applications of rock phosphate
fertilizer, which is very slowly soluble. It is
sometimes used as an indicator of the "reserve"
phosphorus supplying power of the soil. This is a
controversial practice and Spectrum Analytic does
not use this value in evaluating soils or making
Sodium is reported both as parts per million (Na
ppm) and percent saturation (Na Sat %). Sodium is
not a nutrient, and it is typically a major
component of the soluble salts value (see the
following section on soluble salts). High levels of
Na are detrimental to both plant growth and soil
structure, and many of the guidelines are based on
the percent saturation of Na.
Soluble Salts (Salts)
Soluble salts are reported as a measurement of
electrical conductance of the soil solution called
millimhos/centimeter (mmhos/cm). This value
increases as the salt content of the soil increases.
High levels of soluble salts are generally damaging
to plant growth. However, plant tolerance of soluble
salts is highly variable between species.
Nitrate-N is the predominant form of N used by
most plants. It is also the form most easily lost
through adverse environmental and soil conditions.
The level of nitrate reported is NOT used in the
nitrogen recommendation due to the many variables
that can affect ultimate plant availability.
Soil texture refers to the percent sand, silt,
and clay contained in the soil. The proportions of
these components determine the name assigned to the
soil (sandy loam, silty clay, etc.) as shown in the
USDA textural triangle. The name of the texture is
reported in one column, with the percentages of
sand, silt, and clay in the following 3 columns.
This information has several applications, but is
probably used most frequently to identify drainage
characteristics of the soil