You’ll Never Plough a Field by Turning it Over in Your Mind

We’ve known for aeons that ploughing land can cause damage. But just how much damage is now becoming clear. To understand the damage, we’ll have to consider many things.

First is the physical. Erosion is a massive problem. We’re losing soil, on a global scale, on ploughed land, about 100 times faster than it can be made, according to the International Panel on Climate Change’s 2019 Land Use Report. Wind and water erosion take hold on the ground laid bare by the plough. There’s also colluvial erosion, where loose soil moves downhill due to the action of gravity. Digging helps promote loss of the sand, silt and clay that make up over 95 per cent of soil. Once exposed, soil is too readily washed and blown away, or carried downhill.

But worse than this. Ploughing, we now know, sabotages something far more delicate – those things invisible to the naked eye.

Every time you plough a field, or dig over your garden, it’s not just the visible soil that’s in trouble, but the soil ecosystem. All those bacteria, protists, nematodes, archaea, algae and fungi, as well as the bigger life, the springtails, rotifers and worms, their home is ruined. Totally stuffed. It can be rebuilt, but it may never be the same. Just like a city, a rebuilt one may differ in lots of ways.

But a few things happen in the interim. Firstly, when you expose this microbial community to the air, lots of them die. When they die, they release carbon, which isn’t replaced in the soil by other living microbes, at least in the short term. Cut open soil, and you release a whole bunch of stored carbon and nitrogen from the rotting vegetable matter as well. But – and this is the kicker – you also cut the hyphal threads, those long, invisible strands of fungal matter that provide all that underground connectivity in terms of nutrients and communication.

These hyphae are the source of glomalin, that magical superglue of soil. Slice through them, and soil structure is broken.

Much of what we’ve done, historically, is about killing, not letting things thrive.

Matthew Evans

Now, glomalin was invisible to science until about 25 years ago, partly because it is so stable. Glomalin can last over 40 years, but the slow depletion of the thing that stores most soil carbon, and does most of the heavy lifting in soil structure – well, that depletion starts in earnest the moment soil is dug. Glomalin’s resilience has, perhaps, allowed us to damage soil with seeming impunity. A grower’s lifetime is but a blip in terms of soil. It would be easy to blame other things – vermin, seasons, the gods – for 40 years of ever so slightly decreasing yields, rather than the plough. And that’s what we did. The plough, after all, was revered.

For centuries a few cultures, independently of each other, recognised the most obvious damage from the plough. They found that rotating crops, planting different things in different years or seasons – in particular legumes to replenish nitrogen – helped. What also helped was a year or two of rest, usually letting the paddock go back to pasture, and allowing animals to graze it. Without realising it, they were letting the underground community regroup and repair.

If we’d worked that out centuries back, then why plough on? We like ploughing because it reduces the weed load, so the planted seeds don’t get outcompeted. We like it because the initial digging gives us that hit of nitrogen for our crops. Ploughing has tamed formerly wild lands and made growing food more manageable, smoothing out bumpy ground.

Often, with your home garden, you’ll still hear people suggest that you dig over the beds between harvests, to ‘aerate’ the soil, to dig compost or other fertiliser into the soil, to cull some weeds. In the short term, this can appear low impact. But in the long term, the damage is profound. It’s a long, slow drip, a leaching of available nutrients, where the soil doesn’t forget, but it can happen too slowly for us to notice in a hurry.

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The good news is that lots of farmers are changing.

Ploughing rates are starting to drop in many places, as no-till agriculture proves its worth.

No-till agriculture, developed in a few cultures – but mechanised for big agriculture in Australia, and now used widely in the United States as well – is a method of inserting seeds straight into the ground in a hole, without the need for digging soil. To suppress weeds, the land is usually sprayed with a herbicide first, most often glyphosate.

No-till agriculture has been a great boon to soil, helping reduce erosion rates and improve carbon storage. Curiously, however, in the United States, where no-till has a strong take-up rate, at about 50 per cent of grain growers, the majority of farmers will still put the plough over the paddocks every few years.

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Unfortunately, no-till is still damaging, however. The International Panel on Climate Change estimates that soil is still lost up to 20 times faster than it is replaced in no-till agriculture. That’s admittedly about a fifth of the rate of loss with ploughing, but it’s still a backwards game. The use of herbicides, the lack of animals and the planting of single species are all possibly to blame.

Along with no-till, artificial fertiliser use is becoming, in some areas, more strategic, less wasteful, and more targeted. That’s a good thing for the farmer, and the farmed. A good thing for soil, and for the environment further afield.

What we do to soil, we do to ourselves

Matthew Evans

In fact, some of the best modern ways to grow grains are in pasture, and to also use grazing animals. Colin Seis, an Australian sheep farmer, has led the charge. He’s perfected a system of direct-drilling grain seeds into pasture. Through a complex series of cropping, resting and grazing, he’s able to grow food and store carbon and build soil life. He does all this without resorting to glyphosate, while keeping living plants in the ground all year around.

On his New South Wales property ‘Winona’, Seis has seen soil nutrient availability boosted 172 per cent on average, and his carbon by 200 per cent. He reckons a lot of farmers still work on what he calls the ‘Moron Principle’, where they keep putting more things on. More nitrogen, more herbicides, more phosphorus.

Through trial and error, Seis has led a global movement to rethink how we grow food. ‘Pasture cropping’, as it’s called now, is practised by over 3000 landholders on 3 million acres around the world. The aim is to cut out inputs, and concentrate on soil health to grow crops. The aim is living soil, healthy crops and a living wage.

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Modern farming has other, more insidious impacts. So much of what we do in modern farming has sped up soil’s oblivion. On balance, some practices are bad for soil. Ploughing is bad. Adding artificial nitrogen is bad. Ditto for adding phosphorus. But so, too, is the rampant use of herbicides and insecticides.

There are now crops that don’t die when sprayed with herbicide, because they’ve been genetically modified to resist them. It seems like a brilliant idea, because farmers can spray the crop, and kill only the weeds (though herbicide-resistant super weeds are a problem).

Since the advent of corn, soy and cotton that are resistant to glyphosate (Roundup), the use of herbicides has reached stratospheric quantities – with around 8.6 billion kilograms (19 billion pounds) of the herbicide sprayed around the world.

The problem with glyphosate, of course, is that it kills not only the ‘weeds’ we see, but the subterranean life we don’t see. Some is passed directly down into the soil as root exudates, immediately having an impact on the rhizospheres. When every plant in a paddock dies, you also lose the entire first trophic (‘feeding’) level – the initial sugars that feed the whole system – because there’s no photosynthesis. And in the absence of fresh sugars from plants, much of the microbial life dies. Fungal populations that are reliant on their association with roots are particularly badly hit. Glypshosate actively compromises fungal colonisation of soil, and blocks the synthesis of essential amino acids by soil microbes. It lowers plant immunity. It’s also been suggested that glyphosate can lead to more plant disease, because its use ‘reduces the overall growth and vigor of the plants, modifying soil microflora that affects the availability of nutrients required for disease resistance’.

In other words, kill the plant, kill the soil – or at least mortally wound it.

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It’s not just broad-spectrum herbicides that deplete soil, so do other tools in the modern farmer’s armoury. Fungicides, which are widely used to discourage mildews and moulds on crops, can depress all those other wonderful fungi that are feeding plants and gluing soil together. In fact, fungicides, herbicides and soil fumigants usually sound a death knell for soil algae, too.

What about insecticides? Surely, they don’t kill soil?

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Growing food is about harnessing the goodness of our land. Much of what we’ve done, historically, is about killing, not letting things thrive. It seemed right at the time. But we do need to be honest with ourselves about what we’ve done right, what we’ve done badly, and what we can do better.

Every time we grow food, something else wants to outcompete it or eat it. That’s the whole reality of life. We can interrupt biological functions to get the food we want, by ploughing, adding artificial fertiliser, using pesticides. But all of these have a cost. Those interruptions affect the air and the waterways, and while the broader environment also suffers, most of the cost is actually borne by soil. Insect communities can rebuild, if left alone enough. Plants can recolonise areas. But soil damage can be long term, because it’s structural, biological and chemical. It’s a three-dimensional ecosystem.

You can’t see all the damage done to our soils by the plough, and by pesticide and fertiliser use – and historically, the damage has been hard to measure. But now we know that damage is caused at the microbial level.

The thing is, soil doesn’t forget. What we do to soil, we do to ourselves.

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Edited extract from Soil: The incredible story of what keeps the earth, and us, healthy by Matthew Evans. Murdoch Books. RRP. $32.99.

Cover image of Charles Massy’s Monaro farm, Severn Park, by Daniel Shipp.