“
Knowing the CEC of your soil can
help you decide on a fertilizer application
frequency, as high CEC soils require less
frequent applications.”
Organic Matter
A soil’s organic matter reading represents the organic
constituents of the soil. Most of it is comprised of plant and
animal residues. Organic matter in the soil contributes to
the soil structure, the soil fertility and the water-holding
capacity of the soil. Soils rich in organic matter (4-5%) will
be more fertile. The organic matter in a soil can contribute
nitrogen, phosphorus and sulfur to the crop.
Sodium Absorption Ratio
The acronym SAR on a soil test report stands for sodium
absorption ratio. It is used to predict water infiltration
problems in the soil and soil-structure problems. SAR
is the ratio of sodium to calcium plus magnesium in
the soil solution. Soils with an SAR greater than 10
are considered to be sodic. Sodic soils have structural
problems, which result in poor water infiltration. The
soil tends to swell when wet and crack when dry.
pH
Soil pH is one of the most important parameters on your
soil test report. The pH level of the soil can tell you a lot
about the potential availability of plant nutrients and about
the possible toxicities of other elements, such as aluminum.
Soils with a pH greater than 7.0 are considered to be
alkaline soils. Micronutrient deficiencies, such as an iron
deficiency, are common in these soils.
Crops grown in soils with a pH level lower than 5.5 might
show toxicity symptoms of metals (e.g. iron and manganese)
and deficiencies of other nutrients like magnesium. Liming
the soil is mostly recommended in such soils. The ideal soil
pH range for most crops is between 5.8 and 6.5, a range in
which most nutrients are available for the crops.
Electrical Conductivity
The letters E and C on a soil report stands for electrical
conductivity. It is a measure of the salinity of the soil. The
EC is most commonly measured in the soil solution. Units
of expression are usually ds/m, mmho/cm or microsimens/
cm, where 1 ds/m = 1 mmho/cm = 1000 µs/cm. The EC is
one of the easiest ways to assess fertilizer levels in the soil, as
well as the yield potential and soil salinity status and suitability for what’s being grown. Different crops have different
tolerance levels to salinity. Above a certain threshold, yields
will decrease. The yield reduction is proportional to the
increase in the EC level.
Soil health is a vast field of study. Getting your soil tested for
common problems is the first step towards correcting poor
soil quality. For more information on any of the soil test
parameters, refer to maximumyield.com.
Guy Sela is a plant nutrition expert and the CEO of SMART! Fertilizer Management, which makes innovative software for
fertilizer optimization. The software provides optimized and fast fertilizer recommendations and helps growers dramatically
increase crop yields and save costs.
Maximum Yield USA | June 2016
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