• Nicola Harvey

The Perfume of Rot

Updated: Sep 14


Tim cupped the dark soil in his rough hands and lowered his face to inhale the perfume of the freshly popped clod. “What does it smell like?” I asked. “Chocolate cake”, he said with a laugh. And he was right. The rich, structured, nobbly mound of dirt had an odour reminiscent of cake – the perfect balance of sweet top notes and earthy undertones.


This encounter with a lump of soil stayed with me when I returned to the farm I was living on a thousand kilometres north of Tim’s high country station in New Zealand’s South Island. One morning, I plunged a spade into the paddock behind the house to discover, with dismay, that the soil I was farming atop had the consistency of packed sand and a pungent perfume that a Twitter friend suggested was indicative of a lack of oxygen. I’ve been obsessed with the smell of the land since, certain it was emblematic of a good farm in step with nature.


For most of my adult life the fragrances that hovered around me were of the city; exhaust fumes, garbage bins, the smell of bitumen baking under the hot Australian sun. Then, in 2019, I returned home to Aotearoa New Zealand to live on a small cattle farm with my Australian husband. We needed respite from the pace of the city and sought refuge, and work, on a lease farm my father ran just north of a small town called Taupō.


I was overwhelmed immediately by heady fragrances that flooded my tired body with a cold, foreign energy. Pine needles rotting under a tree stand tethered me to childhood memories of walking in the deep bush. A sickly sharp wave alerted me to a dead animal beneath the blackberry. Mustiness heralded the return of rain after a long dry period. Each season brought a flood of new smells – oiliness emanating from the dirt tracks, rotting flesh, plant debris decomposing behind the farm sheds. The smells were all big, concentrated top notes that lingered. But what does smell really tell us about the land we walk on?


Perfume wearers tend to gravitate to bold isolated smells. Most scents are constructed from isolates that strip away the imperfections of the source smell. A rose based perfume, such as Chanel N°5, for example, starts with a living rose grown near Pégomas in France but in the process of extracting the fragrance by combining the rose petals with hexane and then reducing the extract further with alcohols the imperfections are stripped away.


Amber Lenihan, a wine maker turned natural perfumer, says the true smell of a rose is layered and complex. Below the sweet top note is the faint smell of faecal matter. I spent months looking after young calves when we first arrived on the farm, feeding them milk twice a day, cleaning pens and forking hay into small troughs. That was my farming training. At the end of each day my overalls would be stained with sour milky manure. I can appreciate why most Chanel N°5 devotees prefer the faecal undertone be removed, but Lenihan is adamant that a balanced perfume has, in the vial as in nature, both a sweet note and a hint of decay. Neither linger on the nose like those heady smells I first encountered when I moved to the farm.


Scent is evocative but soil scientists tend not to rely only on odour when analysing soil quality or fertility – the indicator of good agricultural land. A visual or soil sample analysis has more currency, says Dr Louis Schipper, an environmental biogeochemist who specialises in carbon and nitrogen cycling in soil. Look for aggregate stability, he advises me; the clumps of soil particles that form around organic matter and hang tenuously from root networks when a plant is pulled from the earth.


When Dr Schipper is working in his beloved wetlands - a space that has a primordial earthy smell – a particular odour that peaks above the base note can herald the system responding to a new element, like the presence of sulphur, which smells distinctly like rotting eggs. But that smell alone is not an indicator of a healthy or unhealthy system.


“Microrganisms are completely disinterested in our opinion on what’s healthy or not,” says Dr Schipper, elaborating that we humans have a habit of anthropomorphising soil to align it with good or ill health. If it stinks, it’s bad. Everyone wants the rose without the shit.


The redolent scent of chocolate cake that I’ve been chasing could be a false signal of soil health. It is, says Dr Schipper, most likely a result of volatile organic compounds that become flight ready when decomposing in aerobic soils. A clod popped from the earth is enough to send the compounds wafting up to the nose sparking one’s imagination. But a more pressing concern for Dr Schipper is that the microbes are in a balanced system and supported to do the vital work of decomposition. The smell of rot, can, in fact, have no smell at all.


Not far from where I farm is the world’s largest vermicompost plant operated by the company MyNoke (Noke being the Māori word for earthworm). It is a simple operation, truck loads of carbon and nitrogen-rich industrial waste from timber pulp mills and dairy plants are trucked into a loading bay where the pulpy flecks and sour sludge are mixed then deposited on farmland in long rows. With the aid of hundreds of thousands of earthworms the waste soon begins to decompose reducing over time by eighty per cent.

On the concrete mixing bay where earthworms slither across the wet surface heading for their next meal a faint sour odour floats above a woody smell. But walking down the rows the fragrance is gone, replaced with a hint of fresh wet grass. “The worm farm doesn’t smell,” explains soil scientist and MyNoke founder Dr Michael Quintern elaborating that the trick is to work with nature rather than trying to outsmart it.


The simplicity of the vermicompost operation belies the complexity of the technology and the problem Dr Quintern first set out to solve: how does one get rid of vast quantities of carbon and nitrogen-heavy industrial waste without further compounding the nitrogen burden in waterways and on the land? He looked first at standard technologies such as anaerobic digestion and thermal composting but all proved too expensive without funding or subsidies. The inexpensive option was worm farming.


“As a soil scientist I never really connected waste management with earthworms, but this is what nature developed over the last 460 million years”, says Dr Quintern. “They started to take care of organic waste from animals, from plants, and converting it”. Earthworms, he discovered, were exceptional at breaking down unwanted organic waste matter and extracting potentially harmful excess nitrogen from the system.

As the earthworms at MyNoke consume the carbon and nitrogen waste mix, they’re growing, breeding and building worm tissue and in the process transforming harmful pathogens into useful bacteria that we need in the soil. “I call it sustainable protein for birds and other animals”, Dr Quintern says as we stop next to a long row barely rising from the land’s surface. He plunges a pitch fork into the earth and what’s revealed is the aggregated soil Dr Schipper described – nobbly, structured, light and odourless.


When reapplied to the land after it has been sieved and packaged, this vermicompost is nature’s fertiliser, a perfectly balanced mix of the elements plants crave most. “If compost is black gold, worm casting or worm poo is nature’s black diamonds,” says Dr Quintern.


Modern farming systems have long relied on the application of minerals – or fertiliser – to encourage plants to grow. It’s akin to applying drops of perfume constructed from just isolated top notes. The plants will respond, as humans do to liberally-applied perfume; it’s attention grabbing. But the farm may falter if the microbes and earthworms that efficiently break down organic matter are neglected. “It's all connected and we need to look at the whole thing,” says Dr Quintern.


Eventually I stopped dreaming about chocolate cake and the spikey smells of decay receded. Now I’m transfixed by microbes and 200-odd earthworm species found in Aotearoa New Zealand, and the land around me has started to flourish. The perfume of rot has all but disappeared.


Nicola Harvey is a writer and producer from Aotearoa New Zealand. Her first book FARM: The Making Of A Climate Activist is out September, 2022


Images: Under the pine trees is by Krystle Rakatau. Worms are from MyNoke, photo by Nicola.

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