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Posted on April 9, 2012 | 28 Comments
Spring is in the air, the buds are bursting, the birds are at their nests, young lovers are canoodling in sunny parks, and – before I get too carried away – farmers are spraying s**t all over their fields. For indeed it is fertility in the latter sense that is my topic in the present post.
I’ve talked about woodland and grassland in recent posts, so I feel that I should now complete the set by talking about cropland. With cropland, fertility is a key issue, and I’ll come to it in a moment. But first I want to say something about the permaculture movement, which I mentioned in my last post. Permaculture has been increasingly influential on many home gardeners and urban environmental activists. It was certainly what first influenced me to start thinking about food production and environmental issues. But it’s had less influence on commercial, broadscale growing, the game I’m currently playing. I suspect that many permaculturists might argue that this is because broadscale growing is behind the game. Permaculture emphasises no till growing, perennial crops and maximum crop diversity, whereas commercial growing – and commercial farming even more so – remains stuck on the treadmill of tillage, annual crops and monoculture.
That may be a fair criticism, but I believe there are grounds for commercial growers not only to justify doing what they do, but to return fire to the permaculturists, for cherished ideas such as no till and perennial polyculture can easily become ill-considered dogma. I have no wish to set up an argument just for the sake of it. What I hope to have suggested by the end of this post is that there’s merit in both viewpoints, and together they may help us chart a more considered path towards achieving a long-term sustainable agriculture.
So, coming back to fertility, the first point to make is that our crop plants are hungry things and cropland is hugely more fertilised than is generally the case among wild ecosystems. In stable wild ecosystems, most plants are adapted to cope with low nutrient inputs, or else with irregular pulses of nutrient input (such as when a passing animal urinates in the vicinity) – often being helped in the latter case through association with mycorrhizal fungi (source: J. Philip Grime, Plant Strategies, Vegetation Processes and Ecosystem Properties). In fact, something like half of all the world’s soluble nitrogen results from human agency (source: Vaclav Smil, Enriching the Earth), which is pretty bad news because this uses a lot of non-renewable energy and causes water pollution, greenhouse gas emissions and biodiversity loss.
All that is true of organic as well as synthetic fertiliser, although the problems may be less in the organic case. It’s probably easier for conventional farmers to give their crops the correct amount of fertiliser exactly when it’s needed, but on the other hand synthetic fertiliser probably has higher energy costs and is more soluble, and hence potentially more polluting.
I say synthetic fertiliser ‘probably’ has higher energy costs, because in the organic case a lot depends on where the fertility comes from. Suppose that you buy in a load of municipal green waste compost, or cow manure from a conventional farmer, or horse manure from a local stables. You need to factor in the source of the fertility and the costs of getting it to your site: organic manures are bulky, with low nutrient densities, so once you start trucking them around the energy costs quickly mount up. If they’re from conventional farms then they’re likely to derive ultimately from energy-intensive industrial synthesis, and the same is true if they’re from a stables – or at the very least they’ll derive from a rather questionable land use. I’ll provide some specific figures to back up these claims in a future post (you can also find some on the Research page). It might be argued that the green waste or the animal manures are waste products that might as well be used by organic farmers, but I’m not convinced. If those fertilisers were reused at source it would save drawing down more non-renewable resources in fertiliser manufacture for the next input cycle, and save on transport costs as well. Organic growers buying in fertility in this way are feeding off the bloated body of the fossil fuel economy – it’s a bit like driving to the bottle bank with a few empties in order to ‘save’ energy.
So what are the alternatives? Well, there are a few, but the only one I find really convincing as a general strategy is to grow legume-rich cover crops (‘green manures’), particularly clover – an approach covered in depth in Jenny Hall (now Jenny Griggs) and Iain Tolhurst’s brilliant book Growing Green. The main problem with this from a permaculture perspective is that you can’t easily establish crops into a clover sward; the clover needs to be tilled in first, and according to permaculturists tillage is to be avoided. There are five main reasons why:
For these reasons, a lot of domestic-scale gardeners decide to adopt ‘no dig’ methods and import the fertility from offsite, which isn’t difficult on a garden scale. This isn’t really an option for larger-scale growers, because you can never find and transport enough manure and compost, and this draws you into leguminous leys and tillage. But of course if you perform an energy audit, a thousand home gardeners each importing a ton of compost is not energetically better than one farmer importing a thousand tons of it (in fact, it’s almost certainly worse). Furthermore, I think the objections to tillage should probably be rewritten as follows:
All things considered, I think it’s preferable to grow green manures and till them in rather than adopting no till systems based on imported fertility. I think the permaculture movement and other alternative farming advocates have erred in putting too much emphasis on tillage and too little on input provenance. I don’t doubt that the ‘organic’ gardener who slaps down huge amounts of imported compost can achieve impressive vegetable yields…but then again so can the conventional grower. We need a whole system approach that focuses on achievable sustainable yields.
But green manure systems are still quite crude, amping up the nutrients and potentially resulting in the same problems of over-nitrification that I mentioned earlier. And when all is said and done, it’s best to avoid tillage whenever possible. How wonderful it would be if we could replicate wild ecosystems, with our crop plants adapted to low nutrient input and nutrient pulsing through mycorrhizal associations. That would be true permaculture farming. But let us not run before we can walk. I don’t see the logic of adopting a no till approach on the grounds that it’s more ‘natural’ and then unnaturally importing truckloads of factory-derived compost. Why not first of all focus our efforts on better nutrient cycling, and on optimising organic crop rotations so as to keep tillage to a minimum?
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Hi Chris
Here here – this is a great post. YOu should submit to the Organic Growers Alliance and get some feedback. I have got money to write another book with Tolly but this time aimed at non traditional learners with lots of photos etc and plain english. This argument does need proper airing because I am always uncomfortable with tillage / importing fertility but what are the alternatives at any scale.
BW Jenny
Excuse my ignorance, but what about if you planted a higher acreage and fertilised less. Could you achieve the same yields? You have already mentioned you have surplus acreage…
I don’t think that would work – you’d end up with a whole lot of stunted, unsaleable vegetables. And it’s a lot of work cultivating ground and preparing transplants, so it would be a stretch in terms of labour.
it shouldn’t be more work cultivating the ground if you are using a no dig method though?
i take your point about the crop not being saleable though. i guess i am thinking more of a situation in which the food is grown for consumption by the grower, not selling it, which requires a much more presentable product!
Well it’s true that produce doesn’t have to be such good quality for home consumption, but without adequate fertilisation (ie a lot more nutrient input than you usually find in nature) I think you’d really get very little even for home use, certainly in the case of many important crops such as potatoes.
In terms of labour, there’s a lot of work involved in raising the transplants whether you use no dig methods or not, so the more you have to do the less efficient your labour input is. It may be true that a no dig gardener has to put less work in that a gardener who tills, though somebody still has to spread all that compost around. But if you do a full energy audit that includes the labour/energy embodied in the imported compost, I think the no till energy costs are higher – I’ll post some data on this soon.
When you criticise no tillers for their unnatural acts are you not mixing up the important question of how to treat the soil with the methods chosen to implement the decided course of action? The small scale growers who bring their fertility onto site from elsewhere could just as well be generating their fertility on site. As far as I know once established the no till system does not require more fertility than any other system.
I also wonder if you underplay the role of the biota in maintaining a healthy soil for example mycorrhiza are not the only way that fungi make nutrients available to plants. I doubt that tillage replicates any sort of soil and even bacteria probably find having their world turned upside down to be slightly troubling.
May be your conclusion might be slightly re-emphasised to state:- i) no till should be used where ever possible; ii) fertility should be produced on site where ever possible and iii) if either of these is not possible, for reasons of scale or resource availability, then green manuring with clover is absolutely the next best option.
I’d happily go along with your suggestions, except I’d reverse the order of your first two points because I think producing onsite fertility is probably the most important, and “thou shalt not till” has become such a well-established alternative gardening mantra that a lot of people don’t dig deeper into the issues, if you’ll pardon the metaphor.
Certainly I agree that onsite fertility without tillage would be the best possible system, but quite hard to achieve I think even on a domestic scale – or at least quite rarely attempted, when there’s so much cheap fossil energy available.
I’m not sure about your first point. My objection to no till isn’t that it’s ‘unnatural’. And whether tillage is natural or not, it’s demonstrably sustainable – at least in certain, albeit possibly unusual, biomes such as the one where I live. I agree that it’s probably not ecologically optimal, but I think the alternatives are not energetically optimal, and therefore are probably not ecologically optimal either in the long run.
Green manuring is the way to go, it builds deep soil structure through plant roots. Cultivation can assist this if done with awareness and understanding.
Tines working at low speed in the right ground conditions slowly break the soil in a similar way to a broad fork, allowing moisture in and roots to push deep, this builds organic matter at depth in a way compost cannot. Fungi recover.
Surface applied composts keep the crop roots shallow, they grow into the compost and make less use of the resources at depth.
Tusk rollers work at ground speed and wont pulverise soil, following tines they slowly incorporate mulched greenmanure residue.
Legumes are less important than grasses in greenmanure, the real soil structure comes from grasses.
If the only cultivation you have done is with a rotary hoe, discs or power harrow then you really know nothing about how to cultivate.
To build soil organic matter through plants grown onsite and good cultivation takes skill and experience.
To dump loads of organic matter onto soils and then say look how much the organic matter has increased requires no skill or understanding of soil and nature.
Using plastic tarps over soil is a mistake, the soil needs to interact with the wider environment.
There are professional farmers that have greatly improved soil structure, soil organic matter and biology using greenmanures and cultivation without bringing anything in from outside.
We dont need no till, just good farmers
Some interesting points there despite, if I could make so bold, the rather arrogant tone. How much more quickly might we improve agriculture if we avoided calling other farmers ignorant, unskilled or stupid?
But questions remain about the overall nutrient cycle and the productivity of these systems. You can’t just keep mining the soil of its minerals and waving goodbye to them in the food you export … and if you reclaim them instead of exporting them, well what you have is compost.
Incorporating green manures into soil is important to reduce nitrogen loss to volatilisation. No till will lead to greater nutrient loss if material is left on the soil surface.
A plants energy source is produced in the leaf using light. This transformation into physical substance is driven by energy that radiates earth from space. A plants energy comes from outside the earth and is non living. The giving power of plants on earth comes from a unique relationship with the sun.
An animal takes life (life that plants made possible) as their primary energy source. Carbohydrates from living things are converted to glucose molecules and energy for cells.
Hence plants by nature are creators of life simply by living. Animals are consumers of life and must take from life in order to live.
This is not an intellectual argument, its a living observable reality.
Renewable agriculture?
There are practical methods to farm with low inputs and efficiently, producing quality food, improving soil, protecting water, paying real and fair wages whilst maintaining commercial viability.
Tractors and cultivation can support soil health. The knife didnt kill, it was the person in control of it. The knife can be used to perform life saving surgery or to destroy life in an instant. It is a practical tool with limitations based on the experience and intentions of the operator. Cultivation implements are no different.
Soil Nutrient deficits based on produce out vs inputs applied are an on paper excercise. Good soil structure and quality produce are real and observable to human sense and experience.
Luke, yes yes I understand the difference between autotrophs and heterotrophs. But animals play their part in ecosystems. The issue isn’t about the fundamental biology of plants or animals, but the demands that humans are now placing on earth systems, and how to ameliorate them.
It may be true that “Soil Nutrient deficits based on produce out vs inputs applied are an on paper excercise” but it’s also a “living observable reality” in net exporting farm systems, which can easily include putatively ‘regenerative’ ones, and no amount of marvelling at the quality of soil structure or produce escapes that brute physical fact.
Not suggesting food producers
How farmers approach nutrient inputs is an important question and responsibility.
99% of plant nutrients are free and abundant where plants are grown. Air provides 98% of a plants nutrients via oxygen, carbon, hydrogen and nitrogen.
Importing large amounts of carbon to add to soil is not neccessary to build soil organic matter. Organic inputs high in nitrogen are not needed if living plants that remove N from the atmosphere are utilised effectively.
Plants created soils in association with fungi mineralising rock which made nutrients available to plants.
The majority of carbon used in photosythesis forms sugars exudated from roots, these root exudates form the foundation of life in the soil.
Utilising solar energy plants mineralised rock, built soil, provided a carbon base for soil life and supported most of life on this planet.
Plants are givers more than they are takers.
Sunlight, air and living plants is the most natural, economical and energy efficient approach to maintaining soil fertility. Sometimes minerals are needed to maintain quality and production. Applying these in a natural form supports slow and continued mineralisation
Well yeah, that’s all basically true. But you could argue that animals are givers more than they are takers over their life course, same as everything. The issue is can we create plausible renewable agricultures at this juncture in humanity’s time on Earth, and those 98%s or ‘giver more than taker’ arguments don’t quite cut it at that level. There’s no doubt in my mind that the kind of things you’re talking about are going to be part of the solutions we need … but maybe only a part. Quite a lot hangs on your concession that “sometimes minerals are needed…”
Hi Chris
Your whole argument against no till turns on the assertion that legumes can not be easily be included in a no till system.
My idea of no till allows hoeing to a shallow depth which seems to me to be a practical necessity for some crops. It is perfectly possible to grow leguminous green manures or crops and then clear them, either by hoeing or by mulch/plastic sheet etc. This could be an infrequent occurrence by establishing a grass clover lay and allowing soil fertility to build over several years. A leguminous lay can also be cut and the material spread on nearby beds.
This combined with the most important feature of no till soils (which you do not mention), namely their greater ability to hold soil nutrients and avoid leaching when compaired to cultivated soils (better structure, higher organic matter levels, higher levels of and diversity of soil life) means that the amount of input required is less than for dug soils. This is particularly important for the high fertility soils that are needed for most perennial vegetables were nutrient losses have the potential to be correspondingly higher.
The very reason that I have adopted no/low till is to reduce the need for off site-inputs of any sort.
A system that looses nutrient to ground water and air is unsustainable. Tillage results in a greater loss of nutrient and so is less sustainable than low or no till systems. The adoption of no till will therefore give us more time to figure out a long term solution.
The tillage system may be able to replace N through the heavy use of legumes but this will not help with the other nutrients which therefore will have to come from of site, the source of which will eventually become exhausted not to mention the environmental pollution.
On weed seeds. Were do the weed seeds that ‘come up’ come from? They come from seeds that were once on the surface being buried by cultivation.
Most seeds if left on the surface will either germinate or be eaten by something so not causing a long term problem.
Other advantages of no till are that the high level of organic matter on the surface makes the surface more friable so easier to remove weeds, easier to drill seeds and less risk of capping caused by heavy rain then drying. Also long term sequestration of carbon thereby combating climate change (the cultivation of the worlds soils is a major source of CO2)
Also I do not regard myself as a permaculturalist though I am an advocate of no till.
Thanks
Thanks for your post, Peter. I agree with a lot of what you say, and if you’ve figured out a no till system for yourself that doesn’t import nutrient – particularly synthetically derived nutrient – then good on you. That’s got to be the optimum system and I’d be interested to hear more about it.
There’s a few points in your post that I’d question, however:
– I’d argue that green manuring systems require clover, and if you’re genuinely able to hoe out a patch of red clover then you’re a tougher man than me. Either that, or we need more discussion about what ‘no till’ means – at what point does heavy hoeing become tillage? Mulching is of course a possibility on small scales, but what are you mulching with and at what energetic cost?
– Yes, cutting & composting a ley is a possibility. It’s something that I’ve meant to experiment with, but to be honest it’s quite a faff. I suspect it may not stack up too well energetically. You also lose relatively more productive land with it, and you could easily lose significant nutrient in the composting process too.
– I’m not convinced that no till systems are necessarily better at carbon sequestration. Several studies indeed have suggested the opposite, perhaps because of one of the issues you mention – high levels of organic matter on the surface lead to high levels of nitrous oxide loss.
– Yes I agree with you about weed seeds. Some research studies suggest that tillage can reduce the soil weed bank, but I can’t say that’s been borne out by my experience. Doubtless much depends on the local situation and the nature of the tillage operation. Generally I think tillage puts you on a weeding treadmill. But no till systems still require weeding, and on larger scales that’s pretty difficult to do without some kind of tillage – which is doubtless why most large-scale no till farmers use herbicide.
From the reading that I’ve done, the most effective way to fix N with N-fixing plants is to have a perennial N-fixer established for as long as possible in one spot, which is cut, and the material used to mulch an estblished crop elsewhere.
If I understand correctly, the system which Chris proposes involves a N-fixer being grown for a relatively short period of time, then tilled in and allowed to rot in prior to sowing a crop.
In both of the above systems, N is leached while the N-fixer is establishing itself, during which time little N is fixed. However, with a long-term green manure this represents a smaller proportion of the N which is subsequently fixed.
The crops then grow, and accumulate N.
If the crop is then tilled in, it must be allowed to rot prior to drilling/planting the crop in order to avoid alleopathy (so i’m told). While it’s rotting, N is releaed and leached.
If a long-term N-fixing patch is cut and used to mulch a separate area, which is subsequently planted up, the N is released slower as the mulch gradually rots in the dry above-ground environment. Thus, a greater proportion of the N is released when the plants are more established and can make better use of it. Meanwhile, N-has been removed from the N-fixing patch, stimulating the N-fixer to fix more N.
Lupinus polyphyllus is a long-lived perennial legume – perhaps ideal? Alder lives even longer, but is hard to use as a mulch! However, N is eventually spread to surrounding plants through leaf drop. Alley cropping anyone?
Thanks for this comment Ben – very interesting. I think there’s probably a lot to be said for your suggestions, but I’m not yet totally convinced. With a short-term ley you’d sow it at the end of a rotation when N levels are relatively low and so there’s less to be leached. If you establish it in mid spring you’d also minimise leaching. Also, in what form would the perennial mulch be added – compost? hay? fresh green matter? In each case I think there’s potential for leaching and/or N volatilisation.
If you consider only the soil itself, then I have no doubt that zero till is optimal. But you also have to optimise energy use, crop yields and rotations in the whole farm system. With a perennial mulch on any scale I reckon you’d need a drum mower, hay bob and baler or forage harvester and possibly some kind of composting operation. I imagine you’d also need to take more land out of cropping because you’re only getting the leaf and not the whole plant – I think the energy costs & N losses would start to mount up. And maybe you’d have to have a long-term ley polyculture to avoid disease & leaching problems, which would create management issues of its own. I’m not saying it’s necessarily a bad idea – just that there are a lot of complexities.
What I like about your suggestion is the emphasis on thinking about the timing of the nutrient release, which as I suggested in my original post is where we ultimately need to be headed. Though this of course can apply as much to the no till grower dumping down a load of N rich mulch as it would to the till grower.
Alder & alley cropping is another good idea – I’ve got a lot of alder on my holding, and I like to think that the leaf drop helps, but does it really or has the tree reabsorbed the N by the time it drops the leaves (at the wrong time!)? Root turnover is probably better, so long as you don’t till, but again is it enough? And I imagine you’d still be wanting to add some organic matter to the soil to keep building it which you’d have to get from somewhere.
Much food for thought – would you be able to pass on any references from your reading that you mention?
Can’t help but comment, long after this thread faded.
When I saw the title of the post, I went, oh, someone is finally pointing out that “air” is in part where fertility comes from! Alas, that turned out not to be your point. 🙂
But it sent me scurrying to wikipedia, where I found that air is mostly nitrogen, oxygen, argon and C02, respectively. Strange we don’t speak of “nitrogenization” of the soil when we aerate. Couldn’t it be that when we aerate (as in, till), we bring nitrogen gas to all the tiny soil critters who probably directly fixate nitrogen also… but we only tend to think legumes/fungi.
And what role does argon play in the growth of plants? Has anyone done any experiments regarding argon? I could not find any. (They kill chickens with argon nowadays, though, so it is unlikely that our food lacks it.)
Alright, enough bunny trails this morning.
Interesting point – one I’ll try out on the next friendly soil scientist I meet. I can imagine that annuals in particular would be set up for a big nitrogen input, perhaps from aerated soil, though maybe there are other ways of delivering it. Thanks for the point anyway, it’s thought-provoking.
Hey Chris,
I am new to permaculture ideas (fed up of sitting at a desk) & have asked the same question: Why has it “had less influence on commercial, broadscale growing, the game I’m currently playing.”
A quick google took me to this thread from America:
https://permies.com/t/42835/large-scale-permaculture-system
That then led me to watch this hour-long video from Gabe Brown:
https://www.youtube.com/watch?v=9yPjoh9YJMk
It shows a farmer doing no-till, cropping cropland, growing cattle & growing cover crops interspersed. He appears to have been very scientific in his approach & if you haven’t seen it I recommend it.
Thanks Geoff. I’ve come across Gabe Brown, but haven’t fully familiarised myself with his methods, so thanks for the reminder.
Gabe Brown still needs to use herbicides to knock down cover crops before seeding a cash crop. However, his soil is in much much better shape than that of a nearby organic farmer who regularly tills.
Correct me if I’m wrong, but ‘Nature’ doesn’t produce the biggest bounty when left to itself. A free range chicken is small and skinny compared to a factory farmed chicken of the same age pumped with hormones and drugs.
This is why farming permaculturalists all tend to be hippie-types who are anti-big corporations, anti-capitalism, and anti-wealth because they can’t generate much money.
Hence they say it’s a “lifestyle choice”, because it’s certainly not an economic choice.
I practice no-till gardening in my yard because I’m not concerned with maximum efficiency as it’s not my livelihood, and I like the philosophy. I’ll do it for a few years before deciding whether to change systems. What I also like about it is that is costs nothing if you’re not adding fertiliser or chemicals, but the yields will probably be modest I assume.
y · 22h
Charlotte Anthony
lots of errors in the concept here. . it sounds like he thinks that people who do not till bring in off site compost, and or compost they make on site. i certainly agree that if that is what you have to do to avoid tilling, it does not work on large scale. this is why geoff lawton turned to compost tea. the main big ag folks who do not till use machinery that they buy or rent to plant, then harvest and plant into the left over stalks. they do not need to add any more fertility than this. this works well increasing som and soil fertility each year. a lot of agencies are now renting out no till equipment. some people who have several acres and do no till are using low growing cover crops to cover the earth at all time and plant starts and or seeds into these low growing cover crops. i combine this with microbe inoculations and get many inches of wonderful new topsoil each year like mike hoag’s wonderful picture of his field that he turning compost into. each year (which of course cannot be one on large scale). my method is by far the most energy efficient. also when plants are grown in this way they have few insect and disease problems. i want to mention again that people like graeme sait and john kempf are growing probably together 10 million acres of crops with microbiological farming, minimum imputs, minimum tilling. the one thing i agree with in this article is that permaculture in general is not serving the greater community by not finding methods that work on farm scale.
“it sounds like he thinks that people who do not till bring in off site compost, and or compost they make on site”
Well, that’s exactly what a lot of no tillers do, so yep, I sure do think that – ref conventional no till, along with alternative gurus like Dowding and Fortier. No ‘errors’ there.
The other techniques you mention are more or less promising in different regions and were discussed at some length in my more recent posts on regenerative agriculture. I’m sceptical of the rather extravagant claims made for them in reconciling closed loop fertility with high levels of macronutrient flow off-farm in large-scale commercial farming systems. Time will tell. But we’re not there yet.
Since you mention Charles Dowding. He says that his compost is made up of 3/4 on-site and 1/4 off-site matter. I’m not sure whether the horse and cow manure he brings in is included in that, or if they are composted separately, though.
He runs an intensive quarter acre market garden where he maximises the amount of harvest per square foot/meter. That naturally requires more attention to detail than in larger operations. In the 1980s, he ran a 7 acres market garden which was less intensive.
It would be interesting to know how high a ratio of on-site/off-site compost matter one can achieve with an intensive no-dig market garden, and how far it can scale up. That’s an important factor in determining how energy efficient it can be.
Thanks for a thought-provoking article!