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The fertility loop: a naive introduction to Regenerative Agriculture

In order to redesign agriculture and make it ecologically viable, we have to face an apparently simple problem: are there any sustainable fertility sources?


I am a scientist. Until recently the only job I had ever done had consisted of discovering how the world around me works using the scientific method, and/or teaching about this discovery process. However, I am an active person and I’ve always felt the need to do something and live in harmony within the world around me, rather than observing it from the outside. This has led me and my partner to embark on a long journey towards becoming regenerative farmers. Growing and sharing food, if we strive to see things holistically, means nothing less and nothing more than protecting ecosystems — in particular, the ones we are part of and that involve the cyclical conversion of our energy and time into food.


This puts me in the condition of looking at food production systems, and in particular regenerative vegetable growing, without as much prejudice or confirmation bias as someone who has been a farmer for generations might have developed. On the other hand, I am used to thinking analytically about complex (living and non-living) systems, where the interplay of diverse components leads to unpredictable dynamics. In this article, I will take advantage of this viewpoint to explore a big issue in very simple, non-technical, terms.


After years of studying and observing farming practices and reflecting on them, one of the most interesting (and in my view yet completely unresolved and rarely addressed) issues in organic food production is where fertility comes from. I will refer to this as the fertility problem, which put into general terms concerns the balance of inputs and outputs required for agriculture to be an ecologically sound practice.


Food production as an ecosystemic function

In a food system, we need fertility to grow vegetables. This fertility can be easily imported from highly degenerative practices, such as the mining and synthetic production of chemical fertilisers. Moreover, the way it is commonly introduced into soils and plants is highly destructive: tilling, chemical spraying, compaction due to machinery use, fossil fuel burning are all responsible for the obliteration of wild landscapes that were home to thriving ecosystems.

It is true that we have found solutions to some of these issues, but in my understanding, we have done so only in isolated and hardly holistic ways. Even when the solution has been as holistic as possible, there still are a lot of open questions. These can perhaps be summarised in the following: how and on which scale is it possible to treat food production as an ecosystemic function, where the inputs and outputs are cycled within the ecosystem itself, without gradually leading to its degeneration and collapse?

Classically the solutions to this problem come from a well established (although for some still revolutionary and unrealistic) concept: permaculture. In the words of one of its discoverers:

Permaculture is a philosophy of working with, rather than against nature; of protracted and thoughtful observation rather than protracted and thoughtless labor; and of looking at plants and animals in all their functions, rather than treating any area as a single product system. (Bill Mollison)

Permaculture has worked as an umbrella for many regenerative design and production practices; holistic grazing management, no-till market gardening, agroforestry are only some of these. In permaculture, food is produced prioritising full harmony with nature, thus soils are not disturbed (no-till practices), insect populations are never put to risk (no-chemical policies, way stricter than conventional organic farming), and others. The goal of this design process is to manage a farm as a functioning ecosystem. In this context, regenerative” means that the ecosystem is not only maintained in its full living glory, but also that any damage caused by human or other impacts is reverted.

This sounds ideal, and yet I want to focus on how, in practice, we rarely see this working. I won’t go into a comprehensive and long-winded discussion, because there are a lot of aspects to this, as you may imagine. I will concentrate on a very simple idea.


Plants: food needs food

Plants are the cornerstone of the earth’s ecosystems. Without photosynthetic organisms, nobody would be able to convert the most abundant energy form available to the planet (sun radiation) into anything conducive to more complex life.  However, plants need mineral nutrients in order to produce chlorophyll and organic tissues that allow them to fulfil their ecosystemic functions, one of which is to feed animals, including us. Normally, in nature, plants cycle water, gases and soil elements (carbon, nitrogen, oxygen, hydrogen, etc.) from and into other parts of the living ecosystem. For instance, they fix carbon from the atmosphere into solid soil compounds; they also trade photosynthetic surpluses (sugars) with the soil food web (bacteria, fungi and other microbes that live in their root zone) in exchange for increased phosphorous, potassium and nitrogen in soluble form. As they die and decay, they feed that same soil food web and eventually become feed for new plants. Sometimes they are eaten by animals directly, which return fertility back to the soil through their nutrient-rich excrements.

At this point, it might be useful to point out that not all nutrients are the same. Carbon, oxygen, hydrogen and nitrogen, for instance, are not mineral nutrients; they are present in the atmosphere (as CO2 and H2O) and plants (with the help of soil life) can easily fix them and use them. We refer to these nutrients as mobile. On the other hand, fundamental plant nutrients, such as magnesium and phosphorous are much less mobile. Iron, calcium, copper, zinc, boron are examples of immobile nutrients that are only available in mineral form and they can be hard to recycle once they become inaccessible by plants.

A small farm: the human twist

In human food production systems, this nutrient cycling takes place in a significantly distorted way. As we have come to discover while trying to understand the causes of climate change, even the most mobile elements, like carbon, often accumulate in certain parts of an ecosystem, such as the atmosphere, as a result of human activity. For the sake of simplicity, let’s consider a small organic, no-till farm, which is profitable and provides food for a small community. When food is harvested, some of it will feed the farm’s crew, whereas some will exit the farm ecosystem to become food for the wider community; this represents an output of fertility. On the other hand, in order to keep growing more vegetables, nutrients are imported in the form of animal manures or organic soil amendments; we will call this a fertility input.

The crucial issue lies between those two steps: what happens to the chemical and energy content food as it leaves the farm, and can this be cycled back entirely to grow the same amount in the following seasons?

Obviously, in conventional agriculture, this wouldn’t even qualify as a dream — it would be an outright utopia. Fertility inputs commonly consist of mined minerals or industrially synthesised chemical sprays or powders. It does not take much reflection to realise that depleting the earth of precious minerals without being able to recycle them leads to quick degeneration. If you couple this with tilling and spraying, which make the reliance on these chemical inputs higher and higher as time goes by, here you have our current agricultural cemetery: disappearing and dead topsoil, micronutrient-poor vegetables, which are spoonfed with water-polluting fertilisers and protected with wildlife-harming pesticides.

Organic agriculture, it might surprise you to discover, is not much different. Fewer chemicals are allowed, mainly to reduce impacts on human health, without much care for ecosystem sustainability, let alone regeneration.

Regenerative agriculture according to permaculture principles, on the other hand, may seem to address this problem. Or does it?


The promised land: does permaculture work?

This is obviously a provocative title, but I believe we need to really be open and not scared of phrasing the question in this way — at least initially.

Let’s go back to our small regenerative farm. Here, fertility inputs are mainly compost to be used as mulch (remember: no tilling is allowed!) and animal manures as an organic nitrogen source.

Black gold: is compost a sustainable resource?

Compost is a wonderful fertility source. It feeds life in the soil rather than plants directly, and it stores carbon in the ground. It is produced starting from organic matter, and if this is done locally and on a medium scale, the fuel inputs can be low and sustainably sourced.


But, how is compost made? Organic sources of carbon and nitrogen are required, as well as microbiological activity (mainly fungi and bacteria) water, insulation and preferably other nutrients coming from decaying plant or animal material. Commonly, the nitrogen-rich material is easily provided: animal manures (more on that later), or even just vegetable food scraps. Carbon, on the other hand, comes from wood: either processed (as cardboard, sawdust, etc.) or in its raw form (as woodchips). It may seem that there is nothing problematic with making compost. However, the carbon material at its origin has been subtracted from another ecosystem: a forest. The decaying cellulose and lignin in that wood were precious fertility inputs destined to be cycled back into the forest soil. By using it to make compost for our farm, we are just displacing the impact of our input production; in this case, we are making a known or unknown forest pay for it. Unless we grow forests just for this specific purpose. In that case, how many inputs would this endeavour require in terms of land, human labour, energy inputs? More inputs means, eventually, more food to be produced, which in turn means more compost to be made and therefore more forest to be sacrificed. It’s a vicious circle. The right question to ask is: at what scale can compost production be made sustainable?

Of course, animal manure! Or not?

Another fertility option, either to be used in its concentrated form or as ingredient for making compost is animal faeces. Animals are, after all, the main fertility driver in wild ecosystems. Their digestion process produces nutrient-rich organic matter that serves as a source of food for predators (their meat) and as a source of feed for soil microorganisms (their excrements). Unfortunately, animal manures usually come from animals raised industrially, with high quantities of chemical preventative measures and fed with fodder grown degeneratively.


But our farmers are virtuous and determined to close the fertility loop, so they introduce chickens and livestock on the farm and manage them holistically, allowing them to graze only small parcels of soil at a time (this reduces overgrazing, diseases and improves topsoil regeneration). However, manure is laid directly on the soil that is grazed, and there it does its job wonderfully: the pasture grows in biodiversity, water retention properties, nutrition capacity. And yet, this won’t feed the vegetables in the market garden.


Fortunately, in winter the chickens need to be kept in a barn or polytunnel, and this (if carbon-rich bedding is added) generates deep litter that is very useful for compost production. The same can be done with cows and horses, but it does not take much to see that within this framework, the raw fertility inputs that come from animals on the farm are just the byproducts of a poorly managed ecosystem. In fact, chicken and livestock breeds that are able to withstand winter conditions should be kept on the land, not in a barn or stable, where they need chemical wormer and industrially grown food supplements. Even if we manage to feed them on the hay we grow in our pastures, that is fertility we are subtracting from the pasture — where that organic matter was supposed to decay and feed the soil.  It is worth noting that, on the positive side, animals provide nutrient-rich food that can complement a vegetable-based diet, for some people; this, to some extent, inputs a high density of nutrients from the sun into the ecosystem (ATP in the human body).

The poop equation

Since, as we have mentioned, after all, in natural systems animals leave their digestion byproducts on the ground and decay and die on that same soil, we could strive to do the same. For instance, humanure, collected through compost toilet systems, could be added in the mix and safely returned to the soil. Indeed, this would close (a small portion of) the fertility input directly, because the same people who are eating the farm’s vegetables are returning part of their nutrients to the farm’s soil. And yet, there is an issue of scale even here: is it enough to compost the humanure produced from, say, 10 people to grow enough vegetables for those 10 people? Can this be added to other sources of fertility in such a way that the combination is sustainable and regenerates the soil? This is, in its essence, a physics problem. Energy is transferred out of the soil system when we harvest the vegetables and eat them. Plants have collected it from sunlight, converted it into chemical carbon bonds, we digest plant tissue to get usable ATP out of it. Even if we return our byproducts, something gets lost in the way and must be re-introduced into the system. Obviously, we are lucky enough to have an abundant source of solar energy. Solar inputs come from outside the system Earth, but mineral ones don’t. If we don’t find ways to cycle them back into the soil, either via a small or a large loop, the soil ecosystem degenerates.


Cover crops?

An ancient and very low-input way of reintroducing fertility into the ground is by taking it from the atmosphere with the help of cover crops. This is very effective at solving also another problem: the overabundance of carbon dioxide in the air. Crops can be grown whose sole purpose is to photosynthesize and decay to fix carbon from the atmosphere and deposit it into the soil, together with nitrogen and other elements that the soil food web can transform into a plant-available form. There is a problem, though. Where do the seeds for the cover crops come from? In current regenerative practices, they come from ordinary seed sources. This means that they are produced by degenerative practices. Could you produce the seeds on the farm? This would mean increasing the scale of the operation quite dramatically, to be able to dedicate plenty of space to grow cover crops, and some more to grow cover crop seed. More space means more soil, which means more fertility. Once again, the question becomes: at what scale does this process become sustainable, if not regenerative?


Scale and purpose in a complex system: the importance of asking the right questions

Hopefully, I have managed to provide the reader who is unfamiliar with agriculture and ecology a small snapshot of the predicament we are in.


Small farms can’t easily (or at all) become closed systems, as the work of pioneers such as Richard Perkins, Geoff Lawton, Gabe Brown confirms. As Joel Salatin says,

…actually, what we really do is farming the sun!

At some point, however, on a farm outer inputs apart from solar energy have to be considered. Sometimes it is animal feed or medication, sometimes it is soil amendments or timber for construction. As we saw, despite the regenerative practices of the farm, often importing these inputs ends up sustaining the degenerative process that produces them. But if not on a farm scale, is it possible to design a wider closed system, on any human scale, that does not involve any degenerative steps?


Earth’s ecosystems, starting from the material available on the planet and the energy input from the sun, have been able to establish a cycling balance of fertility that has sustained the development of complex life forms. Homo sapiens is somehow messing with this balance? Are we living a transition towards a new equilibrium point?


Ecosystems are complex: they are full of dependencies, competitions, relationships and other interactions between their parts or between them and the environment they are in. In science, complex systems are very difficult to model because of these complicated, often non-linear links between different components. Doubling one thing up won’t lead to the doubling up of another one. Doubling inputs won’t double outputs; in fact, it might even halve them.


In my view, this predicament should not generate more pessimism that it generates wonder. It should motivate us to look for the right questions, and avoid tiptoeing around these issues (to quote farmer Jesse from No-Till growers).


If we are to close the fertility loop in our food production systems, we have to address the issue on a holistic scale. Organic, regenerative, local are not answers by themselves, but have to be integrated and contextualised within the ecosystem they are implemented in.

  • What is our role within the ecosystem?

  • Why do we produce food? Why are we even here and so eager to remain here in the first place?

  • Can we fulfil our function in a natural way, that is, by satisfying our needs for the benefit of the whole?

  • On what scale should we limit our impact if we are to do that?

  • Is there a way to close the fertility loop on any human a scale?

As a vegetable grower, these big questions can be translated in a very practical way: what crops should I grow this year? Where should I buy my seeds? What compost should I use? Should I heat my greenhouse? — etc.


As a food eater, too: what should I eat this season? How and where is this grown, at what environmental cost? What is my connection to this food? How do I make sure that I return as much of this input back into the ecosystem it came from? — and others.


As a scientist, I could try to encourage people who work on complex systems to contribute to this discourse, with their abstract thinking as well as their quantitative intuition.


Finding a regenerative way of farming is bound to be one of the most important pieces of the puzzle humanity is trying to recompose, after centuries of naiveté. All of us, customers and growers, scientists and agronomists, animals and plants, have a role to play in this discussion.


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