Skip to main content

Soil Health: Level 2 - Soil Structure

Soil macroaggregates create a soil structure which is permeable (by air and water) and stable (resistant to compaction and erosion).
  • Soil aggregates result when Mycorrhizal Fungi bind soil particulates together. To be more specific Mycorrhizal hyphae, or filaments, are responsible for increasing a plants overall root mass. These hyphae extend throughout the soils surrounding a plant, and in their search for water and nutrients end up binding soil particles together. As hyphae die and begin to decompose they release Glomalin into soil systems. Glomalin is a glue-like protein which significantly increases aggregate formation, by gluing organic matter to soil particles. This process, of binding Labile carbons (as you recall, organic matter contributes to the Labile Carbon pool) to soil particles, traps these rapidly decomposing carbons in the soil; thereby storing them for future use and preventing these carbons from being released into the atmosphere.  
  • Humic Acids have been shown to increase aggregate formation. Please see Level 2 - Carbon Compounds for a detailed description of Humic Acid's role in aggregate formation.  When Humic Acids combine with clay particles, we get the Humus-Clay Domain where most of the Nutrient holding and water holding capacity of the soil takes place!
  • Once these aggregates have been formed, as a result of both Mycorrhizae and Humic Acids, water and air can easily penetrate the soil. Macroaggregates can also be described as Water Stable Soil Aggregates. The term Water Stable Soil Aggregate can be a bit confusing. First of all, "Water Stable" means that a soil which contains water stable aggregates will not collapse when water enters the system (these aggregates remain in tact during a slake test, which is a measure of the disintegration of soil aggregates when exposed to rapid wetting); as compared to a soil which does not contain these water stable aggregates and will collapse, thereby preventing water from penetrating. Once you have fostered the creation of water stable soil aggregates, water can enter the systems and form small pools in the aggregates. These pools hold moisture, gases, bacterial colonies and labile carbons, all of which increase soil and plant health.
This image shows a macroaggregate (on the left) holding its structure during a slake test. The cylinder on the right does not clearly illustrate how a compacted soil will prevent penetration of water, but it does show how much soil will be lost as water runs off a compacted soil.
  • Tilling of soil will destroy these structures, increase erosion and create soil compaction. Tilling of soil reduces stability, by destroying the structural web created by Mycorrhizal hyphae.  Tilling destroys worms passages and other structural spaces created by soil organisms. Worm passages are tunnels which help the soil breath, by letting in water and oxygen and releasing other gases. 
  • Please see No Till and Water for interesting information on this topic.
Written by:
Aurora Fabry-Wood
Staff Biologist

Comments

Post a Comment

Popular posts from this blog

Soil Health: Level 2 - Description of Terms (Carbon Compounds)

The  Labile Carbon  is also known as the 'Rapid Cycling Carbon' and its composed of all the Soil Organic Matter that is dead and actively decomposing.  It's benefit to the soil is that it provides a source for minerals that are being recycled as potential plant nutrients, so in a sense it's Nature's fertilizer.  Active Carbon   also known as Reactive Carbon is more complex than the Labile Carbon in that its composed of all the dead and actively decomposing organic matter plus all the living soil microbial community that will eventually die and begin decomposing.   For example, the hyphae of mycorrhizae only live about 5 to 7 days before they die and start to decompose, while the fungus organism itself may live far longer.  Recalcitrant Carbons   are the Humic substances made up of complex organic chemistry, some of which is inert and some of which is very reactive and are powerful biologics, such as the Humic Acids.  Recalcitran...
9 comments
Read more

Fertilizers formulated for alkaline soils of the Southwest

Recently I was in an Albuquerque retail nursery where a fertilizer was being sold that stated it was formulated for alkaline soils of the Southwest.  It contained high levels of iron and sulfur, plus the N, P and K major nutrients.  Do any of the readers care to comment on this type of product?    Pros, Cons, etc.  I have my take on it, but I'll entertain what you want to say about it.  Michael Martin Meléndrez
9 comments
Read more

Growing Pecan Trees in Western Alkaline Soil

It's common to see nutrient and water inhibition compromise the production of pecans in the arid western states, particularly where the soils are high pH, which can tie up nutrients such as zinc, iron, phosphorus and more. Keeping soils moist is also a problem because the regions were we grow pecan are not wet bottomland soils where pecan is native, but are high and dry desert soils where irrigation is essential. If the irrigation water is high in dissolved solids, the problem is made worse. There are many good things Soil Secrets can offer pecan growers that can overcome these obstacles, by improving the moisture management of the soil, improving nutrient solutioning and availability of both the native minerals as well as the purchased minerals, and improving the porosity of the soil so that water and oxygen can penetrate meters deep without the need to subsoil with machinery. How's this done? By using the power of Nature's own bio-chemical called the Carbon Matrix. Starti...
Post a Comment
Read more