Page 21 - GM Fall 2025 flipbook

Part 2:
TO SOIL TEST ANALYSIS
Each category affects one
another, and inadequate or deficient
soil chemistry negatively impacts
physical properties and biological
factors.
TESTING YOUR SOIL
Can we examine our soil test to
determine if the soil’s chemistry is
within range? Follow the procedure
below when scanning your soil tests
to help determine whether the soil
has enough specific elements and if
the key cations are water-soluble.
What do you need?
•  Standard Soil test: Uses an acid to
extract and report the amounts of
elements in the soil and calculate
the base saturation percentage.
•  Saturated Paste test: This test is
like a standard soil test; however,
water is used as the solvent to
report the water-soluble elements
(a salinity test can also be used).
Are both tests required?
Yes, both tests are essential for
ensuring accuracy. The standard soil
test provides information about the
nutrient environment available to
your plants in the soil. In contrast, the
saturated paste test reveals the
water-soluble nutrients accessible to
plants and the soil structure.
Do we need an irrigation water
test? Maybe. This is the next level of
investigation to determine what
could be causing soil porosity issues.
WHAT WILL WE BE LOOKING FOR?
From the Standard Soil tests, review
the percentages of the following four
elements in the following order:
Sodium: less than 2%
Calcium: 68%
Potassium: 5%
Magnesium: 12%
Soil testing through chemical
extraction assesses the percentages
of sodium, calcium, potassium, and
magnesium. These four elements are
alkaline and are commonly referred
to as “bases.” Reports also indicate
the levels of aluminum and hydrogen
will contribute to soil acidity.
Soil tests reveal the soil’s
capacity to attract positively charged
cations, known as Cation Exchange
Capacity (C.E.C.) and Total Exchange
Capacity (T.E.C.). A higher C.E.C.
signifies a greater ability of the soil to
retain positively charged cations.
Additionally, a higher C.E.C. indicates
that it will require more inputs to
alter the nutrient composition
compared to soil with a lower C.E.C.
Principal Base Elements
Sodium should be maintained at low
levels in the soil, at 2% or less of the
total cations. High sodium
concentrations can disperse clay and
organic matter aggregates, reducing
porosity.
Conversely, due to its double
valence, calcium aids in forming soil
aggregates from organic matter and
clay through flocculation. Typically,
calcium is the nutrient required in the
largest quantity to optimize soil
transmission.
The most common sources of
calcium are calcium carbonate
(limestone) and calcium sulfate
(gypsum). These two products differ
in their effects: calcium carbonate
provides calcium and increases soil pH
(as both calcium and carbonate are
alkaline, leading to a rise in soil pH).
When carbonate dissolves, it converts
to bicarbonate. As the soil dries,
excessive bicarbonates bind with
calcium, transforming calcium
bicarbonate into calcium carbonate.
Calcium sulfate provides calcium
but typically does not alter soil pH
(calcium is alkaline while sulfur is
acidic, which keeps the pH stable).
Sulfate can bond with sodium to form
sodium sulfate, which may leach
through the soil. When soil requires
calcium, calcium carbonate is applied
if the pH is below 6.3. If the soil pH
exceeds 6.3, calcium sulfate is used.
The Saturated Paste test shows
whether the key elements are water
soluble and can positively enhance soil
porosity.
1.  Potassium% must be greater than
Sodium%. Potassium meq/l should
be greater than sodium meq/l.
This indicates the wilt pressure
during stress periods.
GreenMaster • CGSA •
21