WE CAN ALL see that the daylight length is getting longer at each end of the day. In less than two weeks, spring officially begins.
For many of you, this is a much-awaited event.
Our beloved North Olympic Peninsula heralds the Spring Equinox, which, translated from its Latin origin, means aequus (equal) and nox (night) or “equal night.”
Scientifically, it is the precise time Earth’s axis is neither tilted toward the sun nor away. But as we leave the darker and cooler days of our always-mild winters for the warmer, florific sunnier days of spring, let us have a scientific discussion on soils and how they truly are the root of all your gardening concerns.
Today, we move on to soil structure.
Structure of the soil refers to type of aggregation (the way the particle size is clumped together) and thus also depicts porosity (pore space) in your soil.
Soil structure is crucial. Just like texture, it directly affects water movement through the soil, root penetration, atmospheric exchange and toxic gas release, as well as soil fertility and pH levels.
So, as you can see, soil structure is a serious gardening and produce-production concern.
Then, too, poor soil structure dramatically increases soil erosion because compacted and low-porosity soils do not allow water to be absorbed easily and causes water to run off.
So let us meet the five categories that all soils clump together as.
These aggregates that can be absorbed in the field are known as PEDS.
A sixth distinction, structureless, completes the full picture of soil texture.
• Platy structure
Like the name suggest, platy aggregates are flat, saucer or plate-like in nature and arrange themselves in horizontal configurations.
Platy structure soils tend to be either in subsurface soils or those soils that have been impacted by traffic, machinery, livestock, heavy-foot movement and severe leaching.
Platy soil structure greatly impedes downward growth of roots as well as water movement. It causes plants to grow poorly.
• Prismatic structure
The opposite of platy, the PEDS in this category are vertical and their depth is far greater than their width or length.
These PEDS also have caps or flat tops and are normally molds of adjoining aggregates.
Water moves rapidly down the sides and the vertical cracks form because of the forces of nature (dry, wet, cold).
Vertical root growth down the sidewalls of these structures further exacerbates the situation.
• Columnar structures
This group of PEDS, much like prismatic, are vertical as well, but columnar PEDS have distinct top faces.
We tend to find this structure in clay-textured soils.
They are dense and heavy and thus are difficult for roots to penetrate.
• Blocky structures
Just like the name says, these PEDS are block-like in makeup or polyhedral, a shape having many faces.
They tend to be the cast of the faces of these structures that surround and touch them, and, again, are found in high-clay-content soils.
These structures have poor fertility and can be humongous.
When tilling wet soil, you can mechanically form blocky structures that will last for years, and you know them as soil clods or soil balls.
• Granular structure
Some books will refer to these structures as “crumby” and this is the term I like to use, because I get to tell everyone “we all want crumby soils.”
For flowers and vegetable gardens, granular structure is the only way to go because these aggregate PEDS resemble cookie crumbs.
These units made up of spherical or polyhedral shapes and have irregular faces that are not cast or molds of surrounding units.
This means there is a multitude of shapes and sizes of particles and pore spaces that allow for slow but well-draining soils that do not compact easily.
Crumby soils allow for superb habitat, hosting the multitude of life that is found in all fertile soils.
This soil will allow for great retention and expulsion of gases and atmosphere.
Granular structure occurs directly in ration with organic matter in the soil, because of their vast array of particle sizes and because minerals are separated by the ever-changing (swelling and decaying) organic matter and the resulting humic acids.
Granular soils are the easiest to cultivate, plant, weed and till, and where earthworms thrive the best.
Next week, we will learn why organic matter changes the game to your soil’s favor.
So until then … stay well all!
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Andrew May is a freelance writer and ornamental horticulturist who dreams of having Clallam and Jefferson counties nationally recognized as “Flower Peninsula USA.” Send him questions c/o Peninsula Daily News, P.O. Box 1330, Port Angeles, WA 98362, or email news@peninsuladailynews.com (subject line: Andrew May).
