June 2024 – Parks & Recreation - 49

Enhancing Soil Education
By Nathan Straume
I
have been working in the park and recreation field for more than 30
years, and I noticed early on that soil education needed improvement.
A few years ago, I decided to start educating our industry with simple
and easy-to-understand soil knowledge.
To understand soils better, we
need to look at the three main
types of soils - sand, loam and
clay. Each of these soils has unique
properties for soil health and plant
growth that contribute to a healthy
plant or tree.
Within these soil types are many
acronyms you might see when
performing a soil test to better understand
your soil and how to fix
or ameliorate it to promote better
plant or tree growth.
* NPK is the acronym used in fertilizers
to indicate the amount of
each element in the product.
* N is for nitrogen, which helps
with leaf color and growth.
* P is for phosphorus, which
helps with root growth.
* K is for potassium, which
helps with flower and fruit
production.
* pH measures the acidity or alkalinity
of your soil. It's measured
on a scale of 1 to 14, with 7 being
neutral. If your pH isn't between
5.5 and 8, then plants likely will
struggle due to nutrients being
unavailable. You can keep adding
fertilizer, but the plant or tree
cannot access it.
* EC, electrical conductivity, is the
measurement of salt in your soil.
Most plants and trees do not like
salt and will struggle to grow.
* WHC, water-holding capacity, is
the measurement of how much
water our soils will hold. Sand can
hold only 7 percent of any water
added, whereas clay can hold 50
percent of any water we add.
* OM, organic matter,
is otherwise
known as compost or humus.
We use OM to increase
the water-holding
capacity
of
our soils. When it starts to break
down, it releases nutrients back
to our plants and trees.
* CEC,
cation-exchange capacity,
is one of the hardest acronyms to
get your head around, but some
understanding of chemistry can
help with this. The soil can hold
nutrition, so when you fertilize,
it stays in the soil for the plants or
trees to uptake. Sand has a CEC of
approximately 10 milliequivalents
(mEq) as clay is closer to 30 mEq.
* WP is the wilt point. Plants and
trees show a lack of water in the
soil due to wilting or stress. Sand
has a wilt point of 2 percent of
water-holding capacity, and clay
has 28 percent.
* PAW,
plant-available water,
is readily available to plants and
trees. All soils take water and
lock it away. Any water less than
2 percent in sand or 28 percent
in clay becomes unavailable to
plants, as the roots cannot take
the water due to the suction force
required to access it.
Understanding
our soils is the key
to unlocking their
potential.
* HC, hydraulic conductivity -
otherwise known as infiltration
rate - is the measurement of
water moving through the soil.
Water moves faster through
sandy soils and slower through
clay-type soils. This is measured
in millimeters per hour.
* AFP, air-filled porosity, is the
measurement of voids in soils.
There is more void percentage in
sandy soils and less in clay-type
soils. Did you know plants and
trees need soil air for their roots
to breathe?
* BD, bulk density,
is the measurement
of the weight of soils
at their maximum or saturation.
We need to understand soil
weight if we are putting soil in a
rooftop garden or planter boxes
on above-ground structures.
It still amazes me that these acronyms
are all linked, and by altering
one, you can affect the others in a
positive or negative way. Adding
organic matter to sand will impact
its WHC, HC, AFP and CEC, to
mention a few.
We need to understand these acronyms
and how they work to obtain
suitable soil for our plants and
trees and the right balance. Understanding
our soils is the key to unlocking
their potential.
Nathan Straume is Brand Ambassador at
TerraCottem (Nathan.straume@gmail.com).
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49
June 2024 – Parks & Recreation

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