Building Great Soil Structure


How do Beneficial Bacteria + Friendly Fungi Help with Soil Structure?

By Volume: mineral solids, organic solids, water and air in the soil

Not many gardeners have the perfect soil. Both heavy clay and sandy soils are problematic when it comes to growing healthy plants. Picture the ideal soil: by volume it is about half weathered rock mineral particles, 5% organic leaf litter, compost and debris, 25% water and 25% air.  This is an ideal balance for good plant growth because roots need air as well as water for good growth.

The way these components are arranged is known as soil structure; important because compacted clays are hard for roots and root hairs to penetrate and because sandy soils allow both water and water-soluble nutrients (which plants need for good growth) to leach away, out of reach of the roots, down through the soil profile.

Individual weathered rock mineral particles come in varying sizes. Some of these particles fit closely together like stacking playing cards or pieces in a jigsaw puzzle, while others are rounded and do not snug together. This variation creates spaces of many different sizes in the soil. These spaces, known as soil pore spaces are essential for storing both air and water and for providing space for microbes, organic matter and essential nutrients.

Somewhere between compacted clay and loose sand is a loam of good tilth, composed of many soil aggregates. Soil aggregates are individual mineral soil particles that are held together in larger “clumps” by moist clay, organic matter (such as roots), microorganisms, or by organic compounds produced by bacteria and fungi. This crumb structure varies in size from microscopic to up to approximately 2 millimeters across (visible by eye).

“Well-aggregated” soils are more stable and less susceptible to erosion, with plenty of room for compost and soil microorganisms. Desirable aggregation affects the movement of water and nutrients as well as plant root growth, counter-act erosion and are stable against rainfall and water movement. Far and wide, from the U.S.D.A. to Australia, soil aggregation is valued.

Soil Life

In addition to those physical components, the soil is teaming with life, from “large” earthworms, insects, mites, protozoa and amoeba, to smaller friendly fungi and microscopic beneficial bacteria. Microorganisms are the hidden magic that allow a healthy soil to flourish. Soil microorganisms produce many different kinds of organic compounds, some of which help to bind the aggregates together and improve the soil structure. Both beneficial bacteria and friendly fungi make important contributions to soil aggregation.

Beneficial Bacteria

One way beneficial bacteria can promote the creation of soil aggregates is by producing organic compounds called “slime” or “biofilm” surrounding and protecting the bacterial colony that attaches to mineral soil particles, organic litter and roots. Biofilms are glue-like in the way they bind soil aggregates together. Plus, polysaccharides in the bacterial biofilm are more stable than plant polysaccharides, resisting decomposition long enough to be successful in holding soil particles together in aggregates.

Friendly Fungi

Friendly fungi also are important in the development of soil aggregates. There are two ways that fungi can be involved in soil aggregation. The first is mechanical.  Fungi grow in long, threadlike structures, called hyphae (pronounced high’fee). Fungi help to form aggregates in the soil by physically enmeshing soil particles with their hyphae and forming a net among soil particles. Mycorrhizal fungi and fungi that colonize fresh organic matter are believed to be the most important for assisting with stabilization of soil particles into aggregates. This fungal mycelial growth has been shown to bind soil particles together more effectively than smaller organisms, such as bacteria.

The second way fungi can form soil aggregates is similar to the bacterial method, A “bio-glue”called glomalin acts as a superglue, sticking nutrient-rich soil aggregates to the hyphae. Glomalin is formed by mycorrhizal fungi and is found in all soils. It is produced in large amounts and is extremely “tough” in that it does not dissolve in water and is resistant to decay. It functions to coat and protect the mycorrhizal hyphae from nutrient loss by gluing together soil particles into aggregates and stabilizing them.

Vegetables reaching optimum growth in soil with good aggregation and plenty of microorganisms.


The effects of aggregation are beneficial to crop plants because they promote good soil structure, reduce wind and water erosion, increase air infiltration into the soil horizon and increase water retention near roots. Further, aggregation reduces compaction which makes for vigorous root systems. Decreased fertilizer and water inputs are necessary with a well-aggregated soil.  In conclusion, the production of excellent soil structure through the development of soil aggregates can be encouraged and maintained by enriching the normal flora/fauna of the soil with the inoculation of friendly fungi and beneficial bacteria.

Adding Beneficial Microorganisms for Growth As Nature Intended

How can a gardener increase soil aggregation and achieve all the resulting benefits?  Adding compost is one way, increasing the percentage of organic matter and resulting in an increase in soil life.

Even easier is by adding easy to use, non-toxic, non-pathogenic and environmentally safe SRT (Seed Root Treatment) by SoilNoc® at, an advanced, broad spectrum mycorrhizal and bacterial root inoculum with beneficial soil biology that jumpstarts and/or restores the beneficial biology leading to great soil structure. Continue to maintain healthy soil through the use of other SoilNoc® products such as PTM+Myco (Pasture Turf Meadow plus Mycorrhizae) and/or CT+Myco (Instant Compost Tea Alternative with Mycorrhizae) for Growth as Nature intended™.


















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