Biological Gardening

Researchers are also starting to pay attention to the non-pathogenic microorganisms that inhabit our bodies.  In fact we cohabit our bodies with at least as many microorganism cells as the 37 trillion human cells that we call our own (and it may be that our human cells are outnumbered three or even ten times) – microorganism genes in our bodies number in excess of one million against a count for the human genome of 23,000.

The fact that, at least by cell and gene count, we’re even more nonhuman than human now seems hard to ignore and, although research pathways here are complex and confounded, initial findings are fundamentally shifting approaches to our understanding of human biology and health.  The presence or absence of particular assemblages of microflora in humans has been linked to syndromes ranging from Alzheimer’s disease and autism, to bowel disease, obesity and to certain cancers.

The Human Microbiome Project and the International Human Microbiome Consortium are signal endeavours exploring the roles of microbes in health and disease states.

Ok, gardening is different – a tree’s growth may be indeterminate and its connection with microorganisms resides largely outside its body.  So, it’s difficult, if not impossible, to find anything like a meaningful cell count for a plant and it’s commensal microflora.  However, the story’s not dissimilar to our own – just on an even larger scale where the richness of soil microflora supporting plant growth measures in astronomical numbers of species, individuals and genes.

The best known examples of plant-microorganism connections are the nitrogen fixing bacteria that occur in root nodules on certain plants (famously legumes like clover and lucerne, but extending to a curious range of other plants such as she-oaks, ceanothus and elaeagnus species) and the mycorrhizal fungi at the surfaces of plant roots.  These exploit metabolites from the plant and in return, greatly expand a plant’s ability to access nutrients and water.

However, soil microbiology extends beyond these celebrated examples to a broader ecosystem within the soil that provisions plants and protects them against environmental stresses and against pests and diseases.

Sometimes we miss the importance of these connections.  Our model for crop research has most often been around measuring crop production in response to fertiliser.

In isolation, this approach can prejudice us to think of soils as essentially equivalent to the inert media in hydroponics, where increasing yield is essentially a response to the ‘right’ additions of fertiliser (and of course water).  ‘Right’ here has caveats – non-organic fertiliser is expensive to buy while organic fertiliser is expensive to transport and often so variable in quality as to defy predictions for crop yield.

Good gardeners, horticulturists and farmers value good soil, but I reckon we’re still not fully across the relationship between the soil, the soil microbiome, the plant and sustainable production.

‘Yield’ obviously depends on the grower’s perspective – a grape grower is likely to focus on quality ahead of tonnage, a certified biodynamic or organic grower will be interested in how the crop is produced, a broad acre grain grower’s measure is of a staple crop that puts bread on our tables and this is likely to be in both tonnes per hectare and quality grading.

As gardeners, we might share some, or all, of these goals.  Of course all growers are interested in the value of the crop and the cost of inputs – and in most cases, in doing good for people, but shifting paradigms is always challenging.

Angus Irwin started Neutrog as a fertiliser business, trying to add value to something he could get for nothing.  He took chook poo from chook sheds, composted it to eradicate pests and diseases, mixed and pelletised it to standardise the product and to reduce volume and weight for transportation.

This involved a lot of learning by doing, both in the factory and in the field, as well as sleeping in his car.  However, Angus is driven, pretty obsessive, wonderfully curious and can’t stop thinking and asking questions.  On his journey he developed some outstanding fertilisers.

Neutrog’s fertiliser development has taken a different route.  For example ‘Sudden Impact for Roses’ was developed with the Rose Society of South Australia and took three years of formulating and testing before that Society would give its endorsement, and a further eight years of trialling before it was endorsed at a national and international level.

Similarly, ‘Strike Back for Orchids’ was developed over many years with the SA Cymbidium Orchid Club, and ‘Bush Tucker’ with native-plant horticulturist Angus Stewart, and soil scientist Simon Leake.

This route has built a very successful business (Angus no longer has to sleep in his car), however, he still can’t stop thinking and asking questions, and his insatiable curiosity continues to take him in new directions – which includes poaching microbiologist Uwe Stroeher from Flinders University along the way.

He no longer runs a fertiliser business – he runs a biologicals business that incorporates organic fertilisers.  Angus has ended up in this space through his own questioning and the development of pragmatic solutions to working with plants, their microbiome and soils.  He’s also ended up where science has ended up.

There’s now strong evidence supporting new approaches to harness soil microflora for sustainable crop production, and clearer indications for caution in the use of antibiotics, herbicides, pesticides and chemical fertilisers that can decimate soil function.

Curiosity has taken Angus to the cutting edge.  Recent scientific papers see human and soil microbiomes as a fundamental part of our past, present and future.  Our future is intimately linked to improving our relationship with microorganisms for our health and for the health of ecosystems, soil and plants.

Explaining how fungal networks communicate and feed the forest

“Soil is by far the most alive and biologically diverse part of the terrestrial ecosystem” writes Maser, Claridge & Trappe, the authors of Trees, Truffles and Beasts.  “Plants obtain nutrients necessary for their growth through the below ground food web, without which the world’s forests would cease to exist.”

To explain in physical terms, forestry tests on a hectare of land in Oregon found that forest soil contained:

• 4.1 tonnes of fungal mycelium
• 5.4 tonnes of mycorrhizal rootlets (fungus roots)
• 40.3 tonnes of woody roots.

In similar Australian tests conducted in a 20 year old pine plantation, it was found that although root biomass accounted for 25% of below-ground carbon root biomass, it consumed 40% of assimilated annual carbon.  How could this happen without beneficial symbiosis occurring?

Mycorrhizae is to soil and plants what a probiotic is to humans – it makes them healthier and stronger.  Acting as an extension of the root system, it turbo boosts the roots’ ability to absorb water and nutrients, which increases plant root development.  A bigger root network improves plant growth, vigour, cropping and disease resistance, as well as reducing transplant stress.

Found naturally occurring in undisturbed soils, like in old growth forests, this soil fungus sends out filaments that boost a plant’s root system, and while mycorrihizae is certainly not a new thing, its benefits are now available to gardeners.  Often referred to as ‘soil inoculant’, it’s that little extra that can make a big difference when establishing plants, especially bare root fruit trees and roses.