Fungi – Organic gardening and their role in the Soil Food Web

Fungi – Organic gardening and their role in the Soil Food Web

Image of fungi in the gardenFungi play a vital role in the soil food web and organic gardening in general, yet they are so very often over looked. That is except for spotting the odd mushroom (the fruit of the fungi) or by the tell tale presence of an unwelcome pathogen. However this does make them slightly more visible than their bacterial co-habitants in the rhizosphere.

Another outwardly visible sign of fungi can be the microscopic white hairs – or mycelia – which in turn are collections of invisible hyphae. You may come across this in the form of certain molds on bread or if you are familiar with the practise of “Supercharging worm castings” you would recognise the “Santa’s beard” effect signalling the increased growth of the beneficial fungi.

A teaspoon of quality soil can contain a number of meters of fungal hyphae – ever ready to go to work for you and your plants!

The fungus in your rhizosphere play a very similar role to bacteria in that they break down organic matter making it available to the plant, crowd out pathogenic fungus with increased numbers and occupy any vulnerable sites on roots reducing the chance of a pathogen taking advantage. So once again it is in our best interests to up the numbers of friendly fungi where possible!

The importance of fungi for nutrient cycling and water control

In terms of nutrient cycling fungi work across the board, transporting Nitrogen, Phosphorous, Iron, Copper etc (not least water) –

Image of mycelia in worm castings
Visible mycelia in worm castings

essentially performing the work of the root, but in an infinitely finer and more elegant manner – Consider the teaspoon mentioned earlier, there would literally be a couple of centimetres of plant root available here yet we are dealing with many meters of fungal hyphae, these same roots aren’t able to release nutrients from the soil, only absorb those already available – It’s those super fine hyphae working between the soil grains, solubilising the nutrients and passing them to the roots, millimetres, centimetres, even meters away, that makes the system work. Also worth noting that if you have a totally organic environment non of those nutrients would be available without fungi and the soil food web.

Without fungi and bacteria organic gardening as we practice it would not be possible – at all

Unlike Bacteria, fungi do not need a particular medium to travel, nor are they constrained much by an open soil structure – this gives them the chance to spread over much larger distances and at a more rapid pace within the substrate. Within these unbroken chains they are able to transport nutrients and water to wherever it’s needed whist also binding the soil together. It’s also worth noting that digging and rototiling destroy these fungal networks rendering them useless. By mulching, adding compost and encouraging worms the digging will be done for you….so please don’t dig. If you’re a container gardener consider this problem and think about replacing fungal networks at the start of the season as you will be less able to build up networks over time in the same way that an allotment holder might.

Specialist beneficial fungi

These types of beneficial fungi are referred to as Saprophytic within the Soil Food Web meaning they live on dead and decaying matter, beyond this we refer to two other specific types of fungus – Mycorrhizae and Trichoderma. Both are more specialised in what they do and both serve particular (and targeted whn used as an input) roles within the rhizosphere. The first is covered in “What is Mycorrhizae?” – but generally speaking is used for yield increases brought on by their ability to form symbiotic relationships with Image of specilaist mycorrhizal fungi that are available for saleplants and “fast-track” phosphorous, calcium, magnesium etc and again water. The presence of mycorrhizae can increase the effective surface area of the root mass by 700 times, in terms of drought protection alone this is a stellar increase – in terms of nutrient transport it becomes far more clear why we mustn’t dig unnecessarily.

Trichoderma bears many of the characteristics already mentioned as well as some “special moves” of it’s own – nutrient transport, yield increase etc aside certain species of Trichoderma are able to invoke an immune response within plants hardening them to disease and attack (See Pythium Treatment using Trichoderma) furthermore it has been observed that species of Trichoderma will literally ensnare nematodes within the rhizosphere, penetrating the body and recycling the nutrients contained within, yet another amazing feat performed by beneficial fungi!

Photo Credits
Fungi in Garden: dandy_fsj

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