I posted a while back about the questions of tillage and fertility, and have since had an interesting debate about it with Patrick Whitefield, one of my favourite writers on matters agricultural and sustainable.

Patrick pointed out that I failed to mention in my post a major drawback of tillage – the oxidation of humus, the loss of which greatly diminishes soil fertility and contributes to climate change through the associated carbon dioxide. He also suggested that tillage gardeners probably import just as much fertility as no till gardeners, and that in any case gardens are high fertility places, so it’s legitimate to import fertility into them.

I think I have to concede all of those points, although I’m still not quite ready to give up entirely on my illicit affection for tillage. What I would say is that tillage is usually best avoided, so in any given situation if you face a till or no till option it’s always best to go for the no till, other things being equal. My point really was that other things rarely are equal, and gardeners sometimes get it into their heads that no till is just A Good Thing no matter what, like Velcro or Nelson Mandela, without putting it into a larger, whole systems context (I fondly recall the furtive whispers that broke out when some visiting permaculture design students set eyes on my rotavator). But if, for example, you compare somebody who grows a green manure ley and tills it in to somebody who buys in a truck full of cow manure, and you trace back all the environmental and energetic consequences of those two approaches, I don’t think it’s at all clear which option is best – in fact an analysis I did suggested that the tillage option would be better, but there are so many assumptions and difficulties with the data that I certainly wouldn’t want to stick my neck out on that one. Even so, I’m uncomfortable with the idea of importing bulky organic composts as an ongoing part of any putatively sustainable farming or gardening system, till or no till.

As Patrick points out, if you grow the fertility yourself on your site and figure out ways of getting it to your crops without tillage – as for example in John Jeavons’ methods – then that’s got to be the best system of all, and I’d agree. The problem really – which actually is a problem underlying a lot of the issues I discuss in these posts – is that such methods are quite labour intensive. They work well on garden scales, and less well on commercial scales. Large-scale commercial no till involves heavy herbicide and synthetic fertiliser applications – is that better than large-scale organic arable, involving heavy tillage? I don’t know.  Generally speaking, I think the more time spent by the more people growing stuff on the less area the better off we’re likely to be in all sorts of ways, but exactly where to draw the line is tricky.

There are other issues in the till/no till debate, some of which I mentioned in the previous post – for example leaching, soil biota, weeds and animal pests. One argument in favour of a green manure/ tillage regimen is that overwintering green manures prevent winter nutrient leaching. I’ve heard it said that really this is more of a problem with ‘conventional’ farming employing soluble nutrients, but I’m not entirely convinced – if you leave your well rotted compost out in the rain all winter I don’t think there’ll be much nitrogen left by the spring, but if anyone has any data on this I’d be interested. Physical weathering damage is also an issue.

On soil biota, tillage is pretty destructive (mostly of macrofauna), but not necessarily to the extent that it compromises the growing system so far as I understand the ecology. After all, a field or a garden bed is a heavily manipulated environment – and everyone agrees that there’s no such thing as a naturally balanced ecosystem anyway! On weeds, again I’m not sure – tillage can certainly put you on a weed treadmill, but then green manures can suppress weeds. Basically, there will be some kinds of weeds adapted to whatever regimen you choose to adopt, and it’s quite hard to judge which weed presentation is optimal – though I could probably be persuaded that no till approaches are generally better, at least on a small scale. On animal pests, here’s two photos of a little experiment we did this year – squash on the left transplanted into tilled grass/red clover and squash on the right transplanted into grass/red clover which was cut but not tilled at transplantation (the latter being the grassy bit with no discernible squash). The squash in the untilled bed were completely hammered by slugs (well, it was a bad year for it…) and possibly also suffered from competition and/or shading. Of course, this isn’t an argument against no till methods in general, though sadly it may be an argument against a specific method that otherwise might have combined the best of both worlds – a minimum till green manuring regimen with only occasional tillage.

Anyway, now that I’m not so tied up with commercial growing, I think I might try to run some little experiments comparing various different methods of till and no till growing. More on that soon. In the mean time, I think my message is: don’t till if you can help it – indeed, in the light of Patrick’s comments, even more so than I previously suggested – and if you do till, do it as infrequently and judiciously as possible. But always think about whole systems and not part systems when you devise your growing methods – if you do, it may turn out that an element of tillage could be the lesser evil.

But now I’ve cleared all that up, I’ve got to say that there’s really nothing quite as amazing as sitting in a tractor hooked to a plough with some nice sharp shares and watching the soil unzip behind you as it carves away off the mouldboards. Not the strongest argument for tillage, I admit, but…well, I did say I have an illicit affection for tillage!

A lot of eco-thinking is based on the idea that there is a ‘balance of nature’. If only humanity could figure out how to play its part in that balance instead of jumping wildly on the far end of the scales, the argument goes, then we could assure our own future and that of our fellow organisms.

But is there really such a thing as a ‘balance of nature’? And if there isn’t, does that mean that anything goes as far as we humans are concerned, that we should consider ourselves a ‘God species’, to use Mark Lynas’s phrase, and not allow our horizons to be restricted by the irritating constraints of existing biology?

My answers to those two questions are ‘no’ and ‘no’, and here I’ll briefly attempt to explain why.

There seem to be three distinct levels at which the ‘balance of nature’ is usually invoked – the whole earth system, individual ecosystems and inter/intra-species relationships. At the whole earth system level, the key idea is James Lovelock’s famous ‘Gaia’ theory, which proposes that the Earth is a self-regulating or homeostatic system with a goal – the regulation of surface conditions so as always to be as favourable as possible for contemporary life (Lovelock The Revenge of Gaia, p.208). The problem is right there in that sentence. For it’s one thing to posit homeostasis, and quite another to posit goals. A thermostatically controlled heating system is self-regulating but, unlike its designer, it is not a conscious agent with specific ‘goals’, and there are any number of reasons why the switch may suddenly be flipped. So I’d argue that at the earth systems level forces may exist that tend to conserve various planetary conditions, but this implies no ultimate direction towards a balanced end-state. Lovelock frequently talks about Gaia in the third person as if she is a goal-oriented agent, but he also says that he finds it useful to think of the Earth only as being like an animal, that Gaia is mere metaphor (The Revenge of Gaia, p.20). I don’t think he can have it both ways. If Gaia is mere metaphor (and I can’t see any evidence to suggest otherwise) then the ‘balance of nature’ is at best contingent and provisional, not intrinsic. There are no goals, and no reason to suppose that something won’t come along to switch the celestial heating system on or off. If Gaia truly exists, she must be some kind of mad, amoral scientist, hurling endless germplasm into an indifferent world, throwing curveball after curveball at it (or, being English, perhaps I should say googly after googly), and giggling as she watches whether it can cope. On reflection, I reckon she’s probably a man.

At the ecosystem level, I think we tend to overestimate natural balance partly because our short lifespan makes us perceive stability where ultimately there is none, and partly because we humans have largely succeeded in extracting ourselves from specific actual ecosystems. If we go for a hike in the woods it’s easy to marvel at the natural balance of the biota surrounding us, but ‘natural balance’ may not be the best descriptor for the relationships between actual organisms fighting their numerous battles for position in the woodland, except as an ex post facto description of the outcome of those battles. Similar arguments apply to natural succession. It’s tempting, for example, to think that nitrogen-fixing pioneer species work collaboratively with successor species to enrich the overall environment (with alder playing John the Baptist to the oak tree’s Jesus, for example), but biological research suggest that the priority has more to do with the superior colonizing strategies of the pioneer plants than of any necessary relationship between the two (Begon et al, Ecology, p.481-2). And the boundaries of ecosystems are never rigid, always in flux, always exchanging energy or other inputs at the margins…

At the inter/intra-species level – well, after many years of Social Darwinism proclaiming the competitive struggle for existence, red in tooth and claw, that now all looks rather more like the self-image of an aggressively expanding colonial society than anything deeply grounded in empirical science. But by the same token the stories we now often like to tell ourselves of biological coexistence and cooperation may reveal more about our own modern preconceptions than anything about the world beyond our window (indeed, coexistence can result from what ecologists call the ‘ghost of competition past’ and even genuine symbiosis in nature often turns out to be at another organism’s expense, such as the conspiracy against giraffes worked by acacias and ants). All in all, I suspect that anybody choosing to pin their colours to a particular point on the continuum between savage competition and blissful harmony as a description of biological process is as right, and as wrong, as anybody choosing an entirely different point. Better, I think, not to choose a point at all.

So if there is no real ‘balance’ in nature, does that mean that we humans should feel free to mess with it however we please? I’d like to answer ‘no’, and here’s why. Environmental philosophers have long attempted to show that living things have ‘intrinsic value’ aside from the values that humans place upon them. I don’t think they’ve succeeded, which in some ways I find regrettable but in others a relief, since the biocentric nature ethics of somebody like Paul Taylor puts you in a serious quandary about whether it’s ethically acceptable to actually eat. To be honest, I’m no longer terribly interested in debating the finer philosophical points of such analyses, but I find the writings of Aldo Leopold (eg. ‘The land ethic’ in his book A Sand County Almanac) and his latter day interpreters like J. Baird Callicott (eg. Beyond The Land Ethic) instructive. I’d offer the following brief encapsulation of their arguments in layman’s language: the natural world is complex, humans don’t understand all that much about it, and we gain when we try as much as possible to empathise with and learn from others rather than subordinating them to ourselves (which needn’t imply that we can’t eat them). Or, as Callicott puts it, “A thing is right when it tends to disturb the biotic community only at normal spatial and temporal scales. It is wrong when it tends otherwise” (Beyond The Land Ethic, p.138).

So if as a farmer I grow cabbages, like all other organisms I inevitably intervene in the biotic community and try to turn some of its resources to my own ends. My activities will be of great interest to others in the biotic community, such as cabbage white butterflies, who will do likewise. I could ignore them, and eat whatever remains of my holey, caterpillar-shit encrusted cabbages. Or I could make further interventions in the biotic community: I could cover my cabbages with enviromesh in a (usually fruitless, in my experience) attempt to stop the butterflies entering; I could plant lovage and yarrow nearby to encourage parasitic wasps to come along and lay their eggs inside the caterpillars until they’re eaten from inside out by the wasp larvae; I could spray the cabbages with a Bacillus thuringiensis preparation, or with pyrethrum; or perhaps I could plant transgenic cabbages with Bt toxin engineered into the genome.

All of these strategies make a determinate intervention in nature, and all will have many biotic consequences cascading down the succeeding generations, but if there is no ‘natural balance’ to which any of them converges which of them should I adopt? Going back to the land ethic and Callicott’s summary of it, I feel most comfortable with the ones somewhere in the middle of the list – ones which I suspect also score on grounds of long-term human self-interest, though sadly not short-term profit. Those middle strategies also appeal to me because I think they probably strike more of a balance between my ends and those of other members of the biotic community. For if ultimately there is no balance in nature, perhaps there’s something to be said for finding a balance in ourselves.

I posted a while back on the issue of annual and perennial plants and the permaculture movement. An interesting debate on the Permaculture Research Institute of Australia website initiated by Angelo Eliades has prompted me to reflect further on the question.

Other than confirming once again that the Y chromosome finds ever new arenas in which to construct its fragile ego, the debate turns on the possibilities for replacing the widespread cultivation of annual plants in global agriculture and horticulture with perennial plants. As explained in my original post and as further outlined in Eliades’s article, the potential benefits of doing so are multiple. The question is whether it’s possible to provide enough nutrients – particularly macronutrients such as energy and protein – to the planet’s vast human population with a purely perennial agriculture.

It’s striking that most wild floras are dominated by perennials, whereas most agricultural crops including the major staples are annuals (wheat, rice and maize provide the majority of global macronutrients). But there are some perennial staples – mostly tuber crops such as potatoes, yams and cassava, although very often these are cultivated as if they’re annuals, thus losing most of the environmental benefits of perenniality. It’s also worth pointing out that since the Neolithic revolution, most of the world’s population has been fed by annual grain agriculture including all of the famous ancient civilisations, with tuber/perennial-based systems dominating in only a few areas such as New Guinea and parts of sub-Saharan Africa (see, for example, Mazoyer & Roudart A History of World Agriculture or Mithen After the Ice). But though relatively rare, these tuber-based systems have proved stable and successful.

Now, an important permaculture principle is to model human landscape design after natural systems, and since perennial plants are so dominant in the wild this alone is enough to make many permaculturists favour perennial-based cultivation. The puzzle then is why it’s proved so relatively rare in human agricultural history. Eliades believes, first, that perennial plants are more productive than annuals, while simultaneously requiring less energy and effort to grow, which would make the puzzle all the greater if it were true. His answer is that, second, the only reason we plant annual crops is because of “arrogance and lack of perspective”.

Both of these claims are so absurd that they shouldn’t really require any refutation. To fabricate a cultivation system that conjures additional productivity out of nothing, while simultaneously  dishonouring the many annual-based farming cultures that have laboured to create viable social ecologies takes a lot of cheek, and is the sort of thing that prevents the wider world from taking permaculture as seriously as it should. OK, perhaps I should register one slight qualification here – as I mentioned some time ago in my post on potatoes, it’s possibly true that grain-based agricultures better suit the interests of state-building elites than tuber-based horticultures (though I very much doubt it’s really that simple), so in that respect perhaps there may be a small role for ‘arrogance’ in the development of annual cereal culture, but not nearly enough to explain its ubiquity.

So we’re back to square one with the puzzle of annual agriculture and perennial flora. In my earlier post, I mentioned Professor J. Philip Grime’s CSR theory as a way to explain the puzzle. Grime classifies plants as ‘competitors’ (selected for in high nutrient – low disturbance situations), ‘stress tolerators’ (low nutrient – low disturbance) and ‘ruderals’ (high nutrient – high disturbance). Most wild habitats are low nutrient, low disturbance and are characterised by stress tolerator perennials, with slow growth rates, cautious reproductive strategies and defences against herbivory, all of which tend to make them less appropriate for domestication in terms of yield and possibly palatability.

As Paul Hillman pointed out in a response to my original post, and as Angelo Eliades also points out, there are nevertheless quite a number of highly productive perennial crops such as sugar cane, cassava, plantains, potatoes etc. With my thinking clouded by the perennial vs annual distinction in the context of CSR theory, my initial response was to suggest that these crops were probably less productive than the annuals. Quite how productive they are in terms of yields per unit fertiliser input or per unit solar input in comparison to the major annual crops is something I need to work on some more, but I’ll now readily accept that they might well compare favourably. Because on reflection, the broader point about all of these perennial staples is, I suspect, that they fit naturally into the ‘competitor’ category of high nutrient/low disturbance crops – essentially pioneer plants that quickly occupy and crowd out fertile space (think of the way gardeners describe potatoes as a ‘cleaning crop’, for example) before giving way to stress tolerators in long-term succession. Many woody fruit and nut species also occupy the competitor or competitor-stress tolerator hybrid niches, as Grime has remarked. In this respect, perhaps we can place the three strategies on a continuum of agricultural usefulness (yield and perhaps palatability) from R to C to S. And if we map the annual-biennial-perennial distinction onto that continuum we’ll find most of the annuals and biennials and a few of the perennials at the R/C end of the spectrum, and most of the perennials at the S end.

That, at any rate, is my working hypothesis. It explains why agriculture and horticulture tend to favour R and C strategists and invariably try to prevent ecological succession (by ploughing, mulching or burning), and this in turn explains why our cultivated plants are mostly annual and biennial but with a number of important perennials.

All of this matters because C strategists – whether annual or perennial – are essentially short-lived, high nutrient demanders, so they don’t exempt us from the fundamental agricultural tasks of generating fertility and preventing succession. This shouldn’t be all that surprising, because in the spartan energetic economy of nature, nobody can expect a free lunch. The more we try to push productivity, the more we need to fertilise and curtail succession, and the more perennial agriculture starts to resemble annual agriculture (eg. with sugar cane replanted every second year in high output systems). And unfortunately we do need to push productivity, because there are 7 billion people on Earth. I think it’s worth being a little sceptical of anyone who claims to grow all their own food, and even more sceptical of anyone who claims to grow it all from perennials – which is not in any way intended to suggest that I think it’s a bad idea to try. There’s much to be said for abundant polyculture, but we do need to keep an eye on overall yield and energy balance. In that respect, every step towards a more perennial staple agriculture and horticulture is important, and initiatives such as the Land Institute need our unqualified support. But the ultimate goal of a productive perennial agriculture is not an easy one to achieve – to state otherwise on the basis of a simplistic reading of permaculture principles risks discrediting the movement. There’s already far too much snake oil on sale.

I have a lot more work to do to flesh out this basic thesis, but I think that’s enough for now. I’d be interested to hear anyone’s further thoughts on the topic.

A couple of posts ago I mentioned the issue of tillage in the context of the permaculture movement. Here I want to discuss another issue at the core of permaculture that troubles me, namely its emphasis on perennial plants.

A key permaculture theme is to observe the natural world and then apply its lessons in conscious human design. Looking at natural plant communities globally it’s striking that almost always they’re dominated by perennial plants, with only a few annuals. Human agriculture, on the other hand, is dominated by annual plants, with only a few perennials. Supposing we could model our agriculture instead on these natural perennial plant communities – the benefits seem numerous. We wouldn’t need to till, to weed, to fertilise, to worry about soil loss or winter leaching and so on and so on. We would put less labour and less energy into our farming, and reap the benefits year after year.

So why don’t we? The literature sometimes presents the issue as a fateful choice made by our farming ancestors – a preference for domesticating annuals that, once made, was as if somebody had switched the points and committed us for ever after to the single track of a high input annual agriculture. There may be something in this. It’s possible to see why the early cultivators might have focused their efforts around annuals and then, with success, had few options but to stick with it. But this view troubles me because it fits within a narrative of modern progress and enlightenment that I frankly don’t believe – the view that our ancestors were less clever and less capable than us in spotting the possibilities for a truly sustainable and sophisticated perennial agriculture. It seems to me that if virtually all human agricultures have inverted the natural order of things by consistently favouring annuals over perennials in the long term, it’s likely due to strong underlying biological causes that are hard for agriculture to overcome, and not just cultural myopia.

J. Philip Grime’s book Plant Strategies, Vegetation Processes and Ecosystem Properties has given me a few inklings about what those causes might be. I can’t hope to convey the richness and complexity of Grime’s analysis here, but his basic point is that three fundamental plant strategies have arisen in response to three types of habitats – the ‘stress-tolerator’ strategy of a low nutrient-low disturbance habitat (think oak tree), the ‘competitor’ strategy of a high nutrient-low disturbance habitat (think nettle), and the ‘ruderal’ strategy of a high nutrient-high disturbance habitat (think chickweed). The fourth logical possibility – low nutrient-high disturbance – basically keeps plants at bay (think wind-blasted scree slope).

Most natural habitats in this schema are low nutrient-low disturbance, and even the ones that aren’t generally have a successional tendency towards it. The plants best fitted to cope with such habitats are perennial stress-tolerators with highly conservative life strategies. Nutrients are scarce, predators are legion, reproduction is risky – so stress-tolerators grow slowly, live long, reproduce cautiously (often clonally) and invest resources in making themselves unpalatable with prickles or poisons. Competitors and – more so – ruderals, on the other hand, prefer to make hay while the sun shines, investing in fast growth and prodigious reproduction at the expense of longevity and unpalatability. But they require habitat disturbance and/or high nutrient input to stave off the longer-term successional advantages of the stress-tolerators.

It’s easy to see where agriculture fits into this picture. Farming peoples want palatable and highly productive plants, and the way they’re most likely to get them is by interfering in succession and replicating ruderal/competitor situations of high disturbance and high nutrition by tilling and fertilising. The result is an agriculture based around prolific, tasty, leafy and/or seedy, mostly ruderal and mostly annual plants.

Grime’s three types are in some sense abstractions, which admit to hybrid strategies in practice. But there are still strong morphological barriers – it’s hard to be stress-tolerant and quick-growing and palatable. Human plant breeding efforts no doubt can and have pushed hard against some of these barriers, but I suspect we’ll struggle to overcome them altogether. For example fruit trees can be quite stress-tolerant, quite productive and certainly palatable – but they’re not very stress-tolerant, and their productivity has probably arisen through co-evolution with fructivorous animals as a reproductive strategy to disperse seeds a long way from the parent plant, which is no doubt why orchards are so disease-prone, and why organic orchards have been described as “the most challenging frontier an organic grower can face” (M. Phillips The Apple Grower). Likewise, most productive herbaceous perennials seem to be pretty short-lived – competitor hybrids, perhaps. Wes Jackson, probably the best known exponent of breeding for a perennial grain agriculture, reckons that it may take at least 50 years to breed a commercially viable perennial grain crop, but he points out that even if we were to develop only one it would pay dividends (Jackson, New Roots For Agriculture, pp.102-8).

I’m sure it would, and I’m sure that professional and amateur breeders should be devoting themselves more fully to the task – especially in places such as Jackson’s native Kansas where the effects of annual tillage agriculture are so manifestly destructive. But I suspect that it will be challenging. Jackson’s oft-quoted remark that “if your life’s work can be completed in your lifetime, then you’re not thinking big enough” maybe hints at his own sense of the difficulties he has embarked upon.

So where does all this lead? For me it suggests that we should support efforts to breed productive perennials – especially seed-based macronutrient-dense perennials – wherever we can, because annual tillage agriculture is pretty destructive. But it also suggests we shouldn’t bank on these efforts succeeding. It suggests that there may be a lot of good reasons for planting gardens packed with fruit and perennial vegetables, but we shouldn’t (yet) delude ourselves that these are ‘permaculture’ gardens unless we can live off them entirely without any surreptitious visits to the bakery or the chip shop (though talking of chips, a long hard look at tuberous perennials may pay dividends). For me personally, I think it means that I want to devote the majority of my farming efforts to figuring out how to grow annual crops as sustainably as I can, for example through agroecological potato growing, rather than going too far down the perennial route. Because much as I’m enjoying this perennial-intensive time of year, with all those lovely creamy spaghettis con asparagi and rhubarb crumbles, sadly it’s the spaghetti and the crumble rather than the asparagus or the rhubarb that are mostly responsible for keeping my hunger at bay. Oh, and maybe the cream as well…which of course brings us back to grass, probably the most successful perennial agriculture we’ve yet devised.

Successful it may be, but sadly an agriculture based around perennial grass isn’t successful enough to feed a planet of seven billion, at least without falling back on other aggressive ruderal strategists – such as Triticum or the notorious Glycine max. And this raises interesting questions about ‘productivity’. Since we devote a huge proportion of our croplands to livestock fodder, could we perhaps afford to push a little less hard at the productivity boundaries likely to trip up perennial grain culture if we adopted a more vegan diet? Maybe, but would it be enough? Everything points to perennial agriculture working best in low population, dispersed, intensive food gathering situations – in other words something barely resembling agriculture at all, so much as the preagricultural situation from which our early farming forebears emerged.

In Permaculture One, the founding document of the permaculture movement, Bill Mollison and David Holmgren wrote that “Permaculture, unlike modern annual crop culture, has the potential for continuous evolution towards a desirable climax state” (p.7). I think that may prove to be pretty optimistic in the face of the biological realities surrounding plant strategies. Any thoughts?

As mentioned in the previous post, I attended the excellent Oxford Real Farming Conference  a couple of weeks ago. I gave a short talk at it on farm scale polyculture, and I promised I’d post something here about what ‘polyculture’ is all about. In a nutshell, the idea is that instead of growing single outputs or ‘monocultures’ (a field of genetically uniform wheat, for example), it often makes more sense to grow multiple outputs or ‘polycultures’. In my talk, I tried to address some of the many different dimensions of polyculture and illustrate how we’ve tried to implement them at Vallis Veg, with varying degrees of success.

You can download my talk here  - it’s in the form of a PowerPoint file, so you’ll need PowerPoint to read it. At the conference I simply spoke to the pictures. Here I’ve annotated them very briefly to try to convey what I said, whilst naturally losing much of the detail.