Soil Biology

Soil Health and Soil Biology

A small group of scientists and practitioners in the last 20 years have worked to understand the complexities of soil biology including bacteria, fungi, protozoa, nematodes and mycorrhizae. What is not generally well understood is that these microbial populations are significantly co-dependent on plants.  The root mass (rhizosphere) provides photosynthetic by-product nutrients to these biological life forms which in turn provide soil-extracted nutrients and water to the plant. Up to 80% of all plant energy is committed to providing nutrients at root level in exchange with soil biology. The two are completely co-dependent, one cannot exist without the other, making healthy soil biology fundamental to the health of the tree.

With the wealth of decades of biological soil management experience to draw from, G.U.F undertakes this explaining the world wide failure of urban trees. Urban soils have become compacted, toxic and sterile. Many urban soils cannot provide the new NPK conditions required for complex organisms such as trees. The new NPK refers to

  • Nutrients – maintain a balance of all (total, exchangeable and available) macro and micro nutrients in a suitable pH range.
  • Physical soil state – build a physical soil structure with sufficient air and waterholding capacity to maximise plant root establishment and enable beneficial micro & macro life forms to breed, live and grow.
  • Key biology – manage the soil and plants in ways to support the ongoing key biological functions in the rhizosphere. The functions include regulating nutrient uptake, protecting against disease, building soil structure and decomposing dead plant material.

Without these conditions in place trees and urban forest will have short life spans, poor vigour, limited and slow canopy growth, be prone to structural failure and restricted shallow root systems.

A healthy soil is fundamental to growing healthy plants and in keeping a stable natural environment. Healthy Soil = Healthy Tree
In determining soil health there are many factors to consider and address.
Soil Nutrients, Physical structure and Key biology …. The new improved NPK are the main areas of focus in sustainable tree health.

The Key biology which generally live in and around soil organic matter provide an initial baseline. Historic and current usage patterns plus past and present external impacts in and around the tree’s rootzone are all observed and documented in our G.U.F Plant Health Care programs.

This ensures as much as practically feasible that soil health is improved from a known baseline and built to closely match plant requirements.
What makes G.U.F the leader in Plant Health Care is our dedicated attention to detail of the most important aspect of soil health – soil micro-biology.

What happens when soil microbiology is working?

  • Plants are healthier and tolerate adverse conditions better.
  • Plants increase their root depth and penetration in microbial improved soil.
  • Water infiltrates easily into the soil and moves into the medium evenly.
  • Air and gases moves freely through the soil.
  • Nutrient cycling occurs normally so less or no applied nutrients are needed.
  • Nutrients become plant available when the plant needs, in the quantity required.
  • Natural disease suppression occurs in the soil and on the plant.
  • Natural protection of root zone and foliage by beneficial biomass.

The Soil Biological Network

Soil life or The Soil Biological Network as it is becoming better known, is a complex network of individual soil bugs and critters, including a vast array of micro-organisms, which each interact and play important roles in the healthy function of soil with plants.
These organisms exist in a symbiotic relationship with the plant in soil, on the plant leaf and stem surfaces with most activity in the rhizosphere – the soil area closest to the roots. From understanding the principles of soil and plant microbiology, it is easy to realise that Soil Health is predominantly determined by a properly functioning Soil Biological Network – the life in the soil. And so, it makes sense that without life in the soil, it simply cannot be healthy and support healthy plants!
The Soil Biological Network is a diverse set of organisms variously extending through the soil profile ranging in size and function to include:

  • Bacteria
  • Protozoa – flagellates, ciliates and amoeba
  • Nematodes and micro-arthropods
  • Algae
  • Fungi
  • Visible insects, small vertebrates, earthworms, litter and plants.
Rod and Cocci Bacteria, 400 x magnification light microscope
Protozoa – electron microscope picture (note scale of 10um) of a bacterial feeding ciliate.
Protozoa – electron microscope picture of a bacterial feeding ciliate.
Predatory Nematode under 400 x magnification using a light microscope
Earthworms consuming microbiology, mating and laying eggs.

The Soil Biological Network of life in the soil.

Without plants, there would be little or no life on planet earth. Without plants, not enough energy from the sun can be converted through the unique process of photosynthesis into carbohydrates and sugars needed to feed animals. Plants are the original solar panel and a key component in a healthy functioning Soil Biological Network upon which ALL higher life forms depend.
Plants produce exudates (sugars) on their root and foliar surfaces to attract and feed microbiology. These exudates contain a formula or recipe to which the biology responds – usually in support of the plant. The encoding of the formula determines what nutrients and enzymes are required and which microbial actions are triggered to deliver the plant needs whilst at the same time the exudates double as a food source for the biology.
If the plant is stressed, these exudates could attract pests and disease-causing organisms. For this reason, it is important to maintain always an optimum balance of food (nutrients), physical structure and diversity of beneficial micro-organisms to sustain a healthy soil and plant.
When beneficial micro-organisms are applied to the plant surfaces the symbiotic relationship between the microbes and plant is enhanced or even activated. The effect of this can be disease and/or pest suppression, increased plant sugar levels, early maturity of plants and much greater tolerance to adverse environmental conditions.
Different plant types release different exudates thus the sets of microbiology relevant to the plant types change accordingly.
The relationship between plants, microorganisms and other animals has been naturally evolving for millions of years. Since the industrial revolution mans’ ingenuity in building cities, cultivating large tracts of land, applying various fertilisers and chemically supporting plant growth have put immense pressure on, and sometimes even destroyed this symbiotic relationship. Therefore, restoring the Soil Biological Network closer to optimum function and health can only provide many benefits.
A functioning and balanced Soil Biological Network will;

  • Suppress Disease (competition, inhibition, consumption) – meaning no more fungicides!
  • Retain Nutrients (stop or significantly reduce run-off, leaching, and volatilisation)
  • Regulate Nutrients – by making available from soil parent material or locked up fertility from previous fertiliser applications at rates plants require.  (Not applied from a fertiliser bag at rates that do not match plant needs at that time.
  • Decompose Toxins (DDT, dieldrin, benzene, etc) and lock up heavy metals (lead, mercury, etc)
  • Build Soil Structure (reduce water use, increase water and air holding capacity, increase rooting depth, improve soil resilience to temperature flux)
Beneficial nematode-trapping fungi in the act of lassoing a single nematode
The Soil Biological Network you can see without a microscope. Saprophytic fungi breaking down the long chains of carbon found in woody mulch create a white mesh binding this material together.
Actively growing Fungal Mycelium in a woody compost
Fungi bind organic particles together in the strongest physical bond by filament known to man.
Mycelium – the active network of the growing stage of fungi. There can be 7000 km of filament in less than a square metre of actively decomposing plant material.

Mycorrhizal fungi

Mycorrhizae are a special family of fungi (Mycor) attached to living roots (rhizae) that have the ability to break open chemical bonds in soil minerals and convey them back to the host plant. These beneficial fungi penetrate cortical cells of the roots of vascular plants. In more simple terms they have a symbiotic relationship with a plant. The plant feeds the fungi its sugars (carbohydrates) and the fungi feed and protect the plant. Ninety percent (90%) of all plants need mycorrhizae to grow effectively, but unfortunately urban forest landscape management techniques have tortured and virtually killed most of these (good guy) mycorrhizal fungi.
Just some virtues of Mycorrhizal fungi:

  • Attach themselves onto/into plant roots, growing around or into the plant’s cortical cell wall without damaging the host plant.
  • Protect the plant from disease causing pathogens largely by exclusion.
  • On demand of the plant, access more water and nutrients (esp. P, Zn, Mn) with their fine long growing filaments.
  • Hold Calcium and Nitrogen in their bodies to later exchange with plant roots.
  • An efficient accumulator of carbon in the formation of its filaments greatly assisting soil carbon sequestration.
  • Create a stabilising medium by secreting glomalin into the soil to help bind soil particles.
  • Physically holds soil blocks together with the strongest filaments known to man
A plant root – with white mycorrhizal fungi wrapping over it, protecting the root surface from infection and disease.
Stars of Calcium Oxalate attached to fungi seen under an electron microscope. Fungi are known to hold calcium that would otherwise pass through the soil and be lost to plants roots.

What kills soil microbiology?

  • COMPACTION (air/water holding & toxin build-up)
  • FERTILISERS (generally salt based – highly soluble)
  • TEMPERATURE (Drought/heat, Freeze/thaw)
  • MOISTURE (Too wet /Too dry / Poor infiltration/Poor drainage)
  • AIR POLLUTANTS (plant respiration, surface damage)
  • ORGANIC MATTER AVAILABILITY e.g. Leaf fall/mulching
  • WATER QUALITY (run-off and recycled water, toxic storm water)

Root to Shoot Ratio

The root to shoot ratio is the proportion of the above and below ground parts of plants. This ratio is often forgotten as root mass cannot be easily seen or assessed when looking at plants – especially trees.  In urban areas, trees are often found to have low ratios of root mass due to construction damage, poor tree management and the lack of knowledge about the importance of a healthy root zone. A ratio of 1:1 would be at best adequate for a plant to be considered as having a healthy root system. A Ratio of 2:1 or higher would enable the plant to function at a much higher level, and this increase in root to shoot ratio can simply be achieved with the implementation of soil microbial interactions. G.U.F considers root to shoot ratio a major component of Plant Health Care programs, developing greater sustainability for the urban forest by building on the root to shoot ratio of all plants and trees.

Root to shoot ratio – notice the depth and amount of root mass of some grass plants. Now imagine the amount of root mass your favourite tree must have below its branches, and then try to imagine the cities of microorganisms supporting your tree!

Tree Protection Zones (TPZ)

Tree Protection Zones are an essential and fundamental tool that professionals in Arboriculture, Landscape Design and Landscape construction use. They work together utilising these basic standards to ensure the sustainability of landscape projects incorporating existing natural assets, principally trees.
A TPZ will ensure that any construction around the trees’ structural and feeder root systems will not have a negative impact on the health and safety of the trees under consideration. The TPZ will allow a landscape designer in consultation with an arboriculturalist to balance the root damage with root protection, health and growth.
As per AS 4970 2009 Protection of trees on development sites, DEFINITIONS, page 6,
“1.4.7 Tree protection zone (TPZ) A specified area above and below ground and at a given distance from the trunk set aside for the protection of a tree’s roots and crown to provide for the viability and stability of a tree to be retained where it is potentially subject to damage by development.”
Using G.U. F’s leading methods, some recovery of roots can be accomplished in support of the continued survival of root infringed trees. This said, we strongly advocate compliance with the Australian Standards 4970 – 2009 to reduce the risk of tree failure resulting in possible damage to people and property.

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