Peak soil

"Dirt" (2008) by David Montgomery deals with the relation between soil erosion and civilization collapse. It is neither the first nor the only book that examines this subject. It is, however, written by a soil scientist, and it brings to a deeper level the understanding of how soil disappears and how this affects agriculture and, in turn, society.

Was the Roman Empire doomed by the loss of fertile soil to erosion? This is a much discussed point that I also examined in a study of mine on the fall of the Roman Empire. Fertile soil generates food that, in turn, causes population to increase and that is what makes an empire able to expand, as all empires do. But fertile soil is also subject to overexploitation. It is fragile; is easily washed to the sea by rain. And, when it is gone, it takes centuries, at least, to reform.

So, did the Roman Empire collapse because of soil loss? Historians are still debating this point but, in this book, "Dirt", David Montgomery makes a forceful case that soil erosion was a major cause of the decline of the Roman economy and that, in general, it strongly affected ancient civilizations. Montgomery connects the dots of what we know and shows - among other things - that the Romans clearly understood the importance of agriculture in their economy. Yet, they never were able to understand the role of soil erosion.

Of course, there are alternatives to the simple linear chain of positive feedbacks that goes as more people -> more land cultivated -> more erosion. The sources tell us that many fields went uncultivated at the time of the Roman Empire and that suggests the possibility of a problem of underpopulation. The military needs of the late Empire were so strong thet there were not enough people left to cultivate the land. There is also evidence of droughts at the time of the decline of the Empire which would have affected agriculture, too. None of these explanations excludes the others. In a complex system, there is no simple cause and effect relation. Everything affects everything else and you need good quantitative data to understand the weight of all the factors involved. Unfortunately, good quantitative data is exactly what we are missing for the Roman Empire. But, on the whole, it is clear that soil erosion is a major element at play in the decline of civilizations. The Romans, as many other civilizations before and after them, were destroying their resource base, soil, and they never were able to replace it.

There is much more in Montgomery's book - it is a comprehensive review of the relation of soil erosion and the history of humankind that starts from the end of the last ice age and arrives to our time. As such, it is a great learning experience. Of course, the book is not without defects. Stuart Staniford correctly points out that often Montgomery doesn't give a sufficient justification for his statements and that leaves the reader unsatisfied. This is true especially for the last chapter, where the text becomes somewhat ideological when Montgomery tackles fields which are not his: peak oil, energy, and the economy. The result is that the discussion becomes shallow, unlike the rest of the book.

Apart from these problems, "Dirt" is an absolutely must read for the serious students of civilization collapse. It is the same for those who still insist in defining biofuels as "renewable energy."

This is certainly an appropriate follow-up to yesterday's post by Robert on biofuels. Ramping up biofuel production can only accelerate the depletion of perhaps our most critical resource. Even water is self replenishing to some extent. Rebuilding our soil resources on any scale is nigh impossible in the short term. Will we sacrifice our dirt to not only feed a growing world population, but to fuel our growth as well? Predicament or problem?

(Off topic: I just cleared the PV arrays of snow. 3.2kw going to batteries. Panels just love these cold, clear days!
edit 2 hours later: with the cold air and reflection from the snow, PVs now producing almost 20% over their rating. Nice!)

Predicament or problem?

Problem, Chung. Solution: 85% reduction in population! Institute sustainable agriculture, putting back in as much as we take out, and allowing the system to recover.

Craig

This is a great read. Highly recommended.

I wonder if its worth a read - does it have any interesting data to back its conclusions? I'm still looking for a book that would follow Tainter's Collapse of Complex Societies, which among other things did factor in soil loss and loss of fertility as potential reasons for the downfall of the Roman Empire... such ideas are not news anymore, certainly not worth a book...

Is collapse endemic for civilizations? Can a civilization function without perpetual growth: can any civilization function in a way that it can refuse itself short term gains in order to look after its own future - beyond the next financial quarter or election? Or are we destined once more to the Dirt - only this time it might be a while before we can rise up again...

I certainly have no information on Roman era soil depletion, but most recent historians have turned against the "decline" hypothesis. It appears that the Roman Empire was a going concern, of course with all manner of problems, in AD 376. Pretty much the current theory is an old fashioned military explanation with the fall starting with the Visigoth victory at Adrianople. For a, not short, summary see The Fall of The Roman Empire by Peter Heather.

Well, the obvious sister book to Tainter's is Jared Diamond's Collapse, which is more of a recent case study book - and also details deforestation, soil erosion, overpopulation, etc. Yet, it is also lacking in systemic modeling and quantitative details.

Other books I've been meaning to pick up myself, but my attempts have collapsed under the burden of other reading:

After Collapse: The Regeneration of Complex Societies, Glenn M. Schwartz (ed)
http://www.amazon.com/After-Collapse-Regeneration-Complex-Societies/dp/0...

Man and Nature: Physical Geography as Modified by Human Action, George Perkins Marsh
http://www.amazon.com/Man-Nature-Physical-Geography-Modified/dp/1440065462/

The Collapse of Ancient States and Civilizations, Norman Yoffee (ed)
http://www.amazon.com/Collapse-Ancient-States-Civilizations/dp/0816512493/

Questioning Collapse: Human Resilience, Ecological Vulnerability, and the Aftermath of Empire, Patricia A. McAnany, Norman Yoffee (Eds)
http://www.amazon.com/Questioning-Collapse-Resilience-Ecological-Vulnera...

Again, there should be balance to the force - both sides considered with debunking attempts of any obvious truths.

Back in 1981 I bought a book that was a publication of a workshop on Dirt, soils, and the environment. One of the talks printed in the book was on Soil erosion and basically it was very doom and gloom. I knew already a lot of topics in the book because I had been getting Organic Gardening magazine from Rodale Press for a few years already.

At 17 I had already had 4 years of growing my own garden. Having a father in the military did not make for good growing conditions until we settled in this house in 1977.

Erosion was something I had to deal with all the time, the house sets on the curve of the street just at the bottom of about a 10 degree slope, but at the top of a 5 degree slope. Everyone on the right side is higher, and everyone on the left is lower. Built into the back yard, at the downslope corner is a drainage point with a underground culvert.

I brimmed up all around my garden space. Old railroad ties on the back sides and rocks from the growing area on the front side. While I was away living life, the rock wall slowly got covered with soil washing across the yard. This coming august will be 33 years on the same hunk of city lot. And the ground is weathered a lot more than I would like, erosion taking it's toil.

One thing I know for sure, tilling the soil every year is bad on it. Wind, rain, sunshine all damage the soil making erosion just one more nail in the coffin.

With more information I would hope we can change the tide of things to come. But getting people to listen to the change that is needed, is going to be hard. I know I learned the hard way that doing things wrong the first time can make it harder to get back to where you started from to repair the damage and head in the right direction.

Edible Landscaping, which I practice is something akin to forest gardening and permaculture. I grew up as a gardener, and trained in forestry and landscape architecture. There seems at times a lot of positive movement forward to a better understanding of where we need to be. Then at times I fear no one is paying any mind, while the BAU goings on keeps peoples attention away from the coming tidal wave.

Charles.

I hope someone with knowledge of the subject can comment on Chinese agriculture. Earliest millet farming seems to have been some 9500 years ago. Almost certainly much of China was once forested, but is now fields and cities. Their civilization has had major upheavals, but no total collapse, and they still apparently claim continuity with their Shang Dynasty ancestors 3700 years ago.

Modern industry and financial hijinks may finally do in the Chinese, but they seem to be aware of the dangers, if "news" reports are to be believed, and seem more likely to mitigate them than any Western government seems able to do.

The classic work on the subject is King's Farmers of Forty Centuries, and is a must read for anyone on this subject - or just for everyone, really. King documents how East Asian (China, Japan, Korea) carefully conserved their soil and soil fertility by recycling organic wastes, including human wastes, back into the soil, and carefully controlling irrigation and drainage to minimize soil erosion. (He also points out the that East Asian cultural practices of drinking tea (made with BOILED water), and eating vegetables that have been cooked and not raw, are a necessary outgrowth of using "night soil" for fertilizer to minimize the transmission of parasites and pathogens.) The East Asian way of farming kept their civilizations going for forty centuries (and absent the current FF/industrial era, probably could have kept right on going). The East Asian societies were bumping up against Malthusian limits, there really is no permanent agricultural answer around those, but their way of doing things did allow them to support a larger population indefinitely than anyone else has been able to manage.

If you want to talk about sustainable agriculture for any meaningful time period (I don't know if "forever", or billions, or even hundreds of millions, of years is in the realm of possibility), then the discussion really does need to be informed by King's book.

This Wiki: http://en.wikipedia.org/wiki/Agriculture_in_China is a really good post on Chinese agriculture. Wiki doesn't usually do a lot for me, but this one led to some great stuff. I learned, for instance, that Lotus plants have many uses as a food source (roots, seeds, young leaves and flower petals). We have a small 1/2 acre pond at the bottom of our property that I dug primarily to catch soil runoff before it left our property and for irrigation. Several years ago we put a couple of lotus plants in it for their beauty and they have taken over, very happy plants. Nice to know that they can be used as a nutritious food source. There's no telling where a daily TOD journey will lead!

According to this Wiki, 300 million Chinese are employeed in food growing, about 1/4 of the population. This is quite a contrast to the US with, I believe, around 2-3 percent now.

Vanguard the news program, had a show talking about China and the degrading of their farm lands due to water needs in the big cities. There seems to be a small but growing movement to show people what all the progress is doing to their land and how they grow food.

It doesn't help when you build a big dam and drown good living land, wasting all that soil at the bottom of a lake.

Charles.

Also something called deserification is impacting China's land. The Gobi is encroaching, and seems unstoppable. That is what nature is and does. It may be mindless, but it is effective.

Craig

From my studies of long ago, most areas that have turned to desert have been taxed by either man's influence or drought. China is draining a lot ground water, which can feed a region but when it dries up the climate and plants change toward desert. Basically a man imposed drought.

4,000 years and the Gobi just now decides to expand? I have read the same reports that you have, or ones like them. I think from all that I know that we are doing a lot more to cause it than one might think. Over grazing, pumping groundwater away to a city, and to many slash and burn or plow farming methods in the outlining areas.

Charles.

How many of those amazing agricultural processes & methods described in King's book are still practiced in China & Japan today? Have they been abandoned in just one century after working so well for 4000 years?

Cooking has little to do with minimizing parasite load due to agricultural practices since plants and humans don't have common parasites. Most, if not all of the parasites on food come from the hands of the cook. If human or animal manure is used, root crops or plants grown close to the ground need to be carefully washed (by someone with clean hands). Proper composting will kill most of the parasites in manure.

It seems like several things make our situation worse today.

One is the practice of developers to skim off the top soil, and sell quite a bit of it as bagged dirt. People talk about this happening, but I wonder to what extent it is really true. Maybe developers are just not careful in all of their digging to put the top soil back on top.

Another is trying to grow a lot of food on a small area. There is no time to rest the soil. Even if fertilizer is added to compensate for some of the lost nutrients, some of the soil itself washes away, and there are nutrients that are not replaced.

Another is trying to harvest biomass for electricity generation and production of biofuels. This biomass in its natural state could go toward producing more soil which we need.

In a natural system, everything that grows from the soil is returned to it. Extractive agriculture, carrying material away from the soil to be consumed elsewhere, is not natural. So 'sustainable' is a relative term. The 'farmers of 40 centuries' were returning as much as they could, but eventually even their carefully maintained soil would be depleted.

The harvesting of all possible plant materials for biofuel production is the functional equivalent of mountaintop removal for coal extraction.

Extractive agriculture, carrying material away from the soil to be consumed elsewhere, is not natural. So 'sustainable' is a relative term.

I would argue that you're "almost" right.

"Sustainable agriculture" is an oxymoron--a nonsensical term. The outcome is just more consumers of agricultural products.

As far as scraping the topsoil off and selling it. Yes that is common around here, we have in fact bought some of it back in the mid 80's from a farmer, who was selling his land to a house farmer. It wasn't bottom land soil that they sell some places, but it was not as heavy in clays either. Bagging it is usually more like being sold in bulk cubic yard lumps, rather than plastic bags. Some of the "soil" mixs you can buy cheap at Wally World and other hardware places is just mixed and weathered wood chips and sand. Basically dead dirt, that looks dark like the good stuff, but isn't.

If you plant correctly the soil never rests, never needs to rest, because it is a living breathing web of life. If you grind it up with a plow and plant row crops year after year, you basically kill the web of life. I know this sounds all hokey talking about a web of life, but if you look at some of the growing living forests and glades and hedge rows and ponds and wetlands, they never stop growing unless there is a hard freeze, or a dustbowl drought.

Fungi, Worms, nematodes, bacteria in the soil die or are harmed when you expose them to sunlight, most of them are benifical to your soils health. If you have to dig to put in new plants into your design, or when trying a different species, you cover the soil with a layer of mulch to protect it. If you have a dead tree only cut down the top, and leave the rest in the ground as a vertical space to plant on, or be habitat for animals and bugs that make your ecosystem a better place to live.

We have this mindset that we need to plow the fields. When you look at how things grow in nature, no one is out there plowing the field to plant the newest plant to show up. It is seeds moved by wind, rain, and animals (Okay blue jays and squirrels do a lot of plowing hunting for food, but not with a big disc and FFs.)

Our problems are going to be reclaiming the wasted lands we call farms of today. All over the world the practice of tilling huge tracks of land, have finally lead us to where we are today. There are solutions, getting all the information together is the key, and preparing now while we still have some time left, unless it is already to late for some areas to recover.

I hope we don't go down the biomass for cars route.

Charles.

You've just described "One Straw Revolution" by Fukuoka! (Have you read it?) He also prescribes cover crops to affix nitrogen (white clover.) For my new vegetable garden (terraced, raised beds) I applied a mychorrhizzal inoculant to the soil. Am hoping it will help the disturbed soil get back into condition. Also added red worms and mulched everything with straw. (It was not at all easy to get straw here in San Francisco.)

I have not read his book, but I have read about it.

33 years ago I started my gardening experience, But even earlier I listened to my Aunt Leona who I have discribed as having a green forearm, She always had plants growing in her house, and I visited there from an early age, and loved looking and listening.

I tried row growing and tilling, but soon got wise to the ways of things, from reading Organic Gardening magazine, and from just thinking about how things grew better. I have stated that I never saw the need for a yard full of green grass monoculture lawn. I read books like, "Carrots love Tomatoes" and many old ones I found at book sales.

I grew up with parents that grew up in the depression and recycling, and reusing, and budget management were just a way of life.

I used to hoard candy from holidays, making it last months, because that was the only time candy came into the house. Cookies, cakes, sweet breads were there, but not a lot of them either. We drank Coke in the early 70's and I had to take pills with it, I still can remember the negative reaction to Coke, and don't like colas much because of that.

So this has been an on going mindset, sustainable is the way to go, I was a tree hugger before I ever heard the term.

I have been meaning to get your email address and ask you about some of your planting experiences, you can mail me at ceojr1963 over at yahoo. Growing gardens and living sustainable as we can in city spaces is a passion of mine. I don't think I have the money to buy all the plants and seeds I want to add to my place this year.

I crossed several Irises that had been here when we moved here, having learned about Mendel and his peas, in school. Later in life I was a tropical fish breeder, and grew for sale aquatic plants used in the fish keeping arena.

That reminds me, There are lots of pond building and stream saving methods to help you reclaim lost soils through plants that grow in those environments being used in compost and mulching to rebuild soils that have been harmed by harsh farming methods.

Charles.

Charles, I've emailed you. Hope I got the address right.

I read the Fukuoka book twice, thinking I must've missed something the first time around.

No: it's a load of abstraction and philosophizing.

Maybe his "do nothing" farming "method" works on rice crops in some locations, but for a New Englander raising potatoes, beans, and cows, the book reads like a treatise on witchcraft.

MikeB,

What I got from "One Straw Revolution"

Of course it is not "do nothing" but it is very Taoist--to work with nature and the natural desires of the plant rather than work against them.

1) The health of the soil is everything. What happens below the ground is far more important than what happens above.
2) Disturbance (exposing the soil to sun and oxygen) kills mychorrhizal life in the soil.
3) The mychorrhizal life will replenish the soil and make the plants less prone to disease and blight without need to resort pesticides.
4) Compost doesn't need to be tilled in--can be laid on top and worms and the mychorrhizal life will draw the compost down into the soil as it decomposes.
5) Winter cover crops can be grown to fix nitrogen.
6) Mulch protects the soil, reduces weeds, reduces water needs and adds nutrients to the soil as it breaks down.
7) Not always necessary to be entirely weed-free. The idea is to discourage weeds and encourage the plants you want to grow. The roots of the weeds can help keep the soil loose and friable and draw nutrients into it. (As I remember he recommends clipping off the tops of weeds and leaving the roots in place, along with gentle hand weeding.)
8) A tidy plot of crops in nice rows with bare, weed-free dirt, though attractive to our eye, isn't the most productive way to grow crops. Nature seems to like a certain amount of chaos and rotting.

I have no idea if these ideas can work in something bigger than a garden plot, but I am focusing a lot of my attention on my soil.

There are do little gardening methods out there. I have listed them elsewhere, but some of the people to look into are, Robert Hart, Marvin Crawford, and Ken Fern. Ken Fern has made a list of 7,000 plants that he has done research on for eating, healing, garden and household uses. But all three of these guys are growing in the UK, so planting in New England might not be the same. And it won't be the same for Arkansas, or Hawaii. Every place you have people you will have to gear the plantings to the growing conditions you have.

Nothing is totally do nothing, but with planning you can limit the work loads down to below what you'd spend going to work at a paying job.

Find out about as many plants that are native to your area as you can, you might have to do some digging around to find the records. Find out how many plants could grow in your area. Sort through them by what they do for each other, their space in the layers of the web. High, middle, low (trees) herbs, ground cover, vines, root zone.

Landscape Architecture is a designing puzzle, it is not easy at first then you start seeing things as a whole system and everything working together to form a complete picture.

With cows you'll need to look at grasses that will grow in your pasture, hedge plants that they will munch on. The plant mix for you might not work for me, or even a farmer two counties over. But the system does work, getting to that point where your work load is small is the biggest effort.

How many Potatoes are you wanting to grow?

The same question for the beans.

In Peru there were 3,000 species of potatoes grown, some for this, some for that, each one a nitch plant. When we took only a few of them and started this whole culturing of them we wasted a lot of home grown information the locals knew about.

At times during the first years when Christian Europeans came over to the new world they really screwed up ignoring the wisdom of the locals, after all at the time everyone else were just pagans to the Europeans. Jared Diamond's "Guns, Germs and Steel" I bet you have read the book, he talks about what lead us to ruin.

As Heinberg says(my words), we are most likely beyond the point of no return, waiting to late to start fixing the problem.

All in all the Japanese have been growing rice a long time, some things just don't translate as well as we would like.

Charles.

Fukuoka is mostly about attitude, rather than method. I was also frustrated at first, seeking a step-by-step 'how-to' method from his writings. We Americans just want to know how to "git-er-done". There is a video on YouTube that shows an elderly Fukoka supervising the creation of a batch of his clay seed balls. I was saddened to hear that he passed away in August 2008, well into his 90's.

interesting. As I recall he discussed what he planted, when he planted and how he planted. He discussed fertilizer and mulch. He described harvest. He described his experimental process and he also discussed the theory/rational behind his decisions. This could be used to determine how to transfer his methods to N. Am. ecologies.

It is true that the book isn`t formatted like a traditional north american `how to` or text book. That could be an issue when reading it. His construction of the book follows, I believe, from his conceptualization of farming as an interaction with living systems in order to extract specific outputs while minimally disturbing overall function or health of the system. This is in contrast to what I call the factory analogue model of gardening or farming - which describes the interaction as input-output overlayed upon and in competition with the local ecosystem.

Just a thought or two - I thoroughly enjoyed his book.
Al

(edit for spelling)

I have an adobe clay garden, couldn't even grow a decent ragweed in 2007 and 2008 no matter how much fertilize I dumped on it. I stumbled across a windfall of leaves, several tons worth, so I'm giving those a try at soil amendment. I spent three afternoons double digging a 4x4 square in the heavy clay so I gave up on that. I took to just spreading a thick layer of leaves in fall of 2008, all of 2009 it was still just leaves. I think this year I finally may get to grow some stuff, worms have been working on the leaves and they've been laying there for 16 months now. I'm reluctant to dig into the ground now that I think I've finally got the soil going in the right direction. I really don't want to disturb the worms and fungus. The leaves have smothered out weeds except for some chicory and curly dock that managed to poke thru, I think I'll just leave those and recruit them as vegetables and try Ruth Stout's methods as long as my supply of leaves holds out.

Do you know what kind of plants grow in your area normally, like 200 years ago for instance? Some places have had the soil weather into bare ground that can't grow anything. It all depends on the place you live, as to what you will be able to do with it as far as the plants you will be able to grow.

If you like we can talk about it further in email.

Charles.

I think it was probably wilderness 200 years ago, Its in the knobs region in Kentucky and too hilly and rocky to be attractive farmland. The lushness of the grass on the slope below my garden plot I think is telling as to where my garden topsoil has gone. Folks at the bottoms of the knobs probably have better soil. The soil is really annoying, can't have lateral lines for septic because the ground wont perc. If you run a tiller thru the ground when its wet it turns into gravel when it dries. Long half inch cracks form all over the place during summer dry spells. The leaves seem to be helping, plus they are free and I don't have to drive out of my way to get them.

For clay soils, and also for sandy ones, adding humus or compost improves them. But having knobs as you call them I get the picture of hills, that have been leached down to the bare clay under layers.

Planting trees, and vines, shrubs and ground cover on the hills/knobs will help, it might take a while for them to establish themselves, but that should improve the soil, make as many of the plants you use food baring ones, fruit trees, or things like Siberan Pea Tree, which is a nitrogen fixer, with an edible seed found in a pod, cooked like lentils.

You might also try Jerusalem Artichokes, they do well in clay soils, marginal soils, just about anywhere.

Our biggest worry is getting the poor soils back up to living soils.

Charles.

In case you haven't seen it, take a look at what this guy did with a farm on poor soil.. great 'Lemons into Lemonade' story.

http://journeytoforever.org/biofuel_library/methane_pain.html

The inert, brushwood compost now provides Pain with still another. use. Once fermentation ends, the big, magic cake produces no more energy, but it will still render 50 tons of natural fertilizer. By spreading a layer of this humus on the poor, stony soil around the house, Jean Pain has created a luxurious farm garden where even tropical vegetables grow. I admire tomato plants two-and-a-half metres high, lift a six-kilo watermelon and inspect a chayote (a kind of sweet Zucchini -- hitherto found only in the West Indies and in Africa), What surprises me most is that these giant vegetables need no watering; all the water they require, Pain tells me, is synthesized in the compost.

Bob

HI Gail,

Builders and contractors don't as a general rule sell the topsoil they remove while building houses-the amounts involved working up a lot at a time or a few lots is not enough to bother.What happens is rhat the building code calls for NO TOPSOIL in the immediate area of the house and its foundations, so it MUST BE stripped off for a good many feet all around, else the house would be sitting in a depression.Once the actual house is finished, the soil, which has been temporarily piled at some nearby convenient spot, is redistributed around the lot.

The problem is that the topsoil may wind up all in one spot, or be buried under subsoil, or all in a nieghbors yard.It really does not make dollars and cents sense to sell the topsoil off a lot and have a hard time selling the new house to be built on it due to a crappy lawn-some builders actually wind up spending serious money on hauling in good soil to make a residential with poor soil lot "work" as business proposition.

This said, topsoil is occasionally sold off residential lots ,this is just not sop, as some people believe.

The soil sold in bulk is usually stripped off of large construction project sites where the volume makes it profitable, or off of nearby farm land where large quantities can be obtained regularly and conveniently.

A site that will be paved or underneath a large building usually needs only a fraction of the original topsoil to be reserved to reestablish the green areas.Selling the rest is just another way to make a buck.

I don't know about now or other parts of the country but in the 1970s west of Chicago in some god awful rich farm country two D-9s would hook up to a big blade and scrape entire large new subdivisions down to clay. The stock piles of top soil were then sold off with a few inches being put back around the houses to carry lawns.

This was a great read, i had read tainter's some years before, and the various roman agrarian laws years before that. This book offered more geographic
breadth and a few insights, i've pushed this book on various intellectual friends. Two small practical actions that this book brought to the fore, was
more "evangelism" towards my suburban neighbors to compost all their grass and leaves and all their neighbor's that will turn it over to them, it won't be
perfect compost but it will be better than their 1.5inches of soil over clay in the yard. The second is to examine and talk about the soils that are
in the banks of the streams to those suburban neighbors, it is deep and dark, it is a place to mine in some bad future if necessary. I have bought some
soil test kits to see if there is anything bad in those soils, something that the book brought out for US soils. There is less of a tendency to use yard
chemicals here than other places I've lived, but there is still some, thankfully there has been no industrial contamination withing many miles and it is
all downstream/downhill.

Tying into the comments posted in the thread on a stable food source. Late in the discussion there were several posts about work being done by people like Ken Fern, Martin Crawford, and Robert Hart. All of them have managed to protect their soils from erosion.

Basically we should take our feet off the land and only walk softly in the grass.

A long time ago I read this comment. Dirt is what you see in a construction yard, and soil is what you eat from.

The soils in my backyard were clay, rocks, and more of the same, when I got here. Now most places it is full of life, and relatively rock free, at least in the growing zone.

I hope we have grown smart enough over the last few decades to realize that we don't have to go on living like we have in the past, we can start to live a more sustainable life.

In Martin Crawford's own words, in another video on the future of farms, he said he could raise enough food for 10 people per acre. With all the plants he and others were building into the landscape, I don't doubt it.

So we say that we can only supply 3 people's food on an acre, doing conservative math. How many acres of selected intensive forest gardening would you need to feed the current population?

A bit over 3.5 million square miles spread out all over the globes growing regions. Okay how many square miles of farms do we have now? How long would it take to stop wasting all the soils we are wasting and gear up to a better living system?

I'll leave it at that for now, It's almost bed time for me. ( I am a night owl, when I can't get outside, the snow is still covering half the yard, here in Central Arkansas.)

Charles.

Did the Romans have a dust bowl and their own version of the "Grapes of Wrath?"

Interesting question leduck. Strictly speaking, the answer is no. There is no record of a dust bowl in Europe during the Roman Empire although we may think of something similar if we look to the fate of North Africa. However, the drama of the degradation of agriculture and of the meltdown of society must have been sorely felt all over. It might have produced some literary work not unlike "The Grapes of Wrath" but, if it ever existed, it didn't arrive to us. The closest document I can think of is "De Reditu" (of his return) by Namatianus, written in the 5th century AD. No dust bowl is described in the book, but the report of extensive silting of the harbors is clear evidence of erosion. The Romans did destroy their fertile soil. Then, Namatianus was a patrician, he had nothing of the social conscience of Steinbeck. He (Namatianus) never could see the degradation of agriculture as a social problem, as Steinbeck did. Maybe there was a Roman Steinbeck, somewhere, but - again - his work didn't arrive to us.

The real decline in North Africa followed the fall of the Roman Empire. It appears to be the result of overgrazing following the time of Mohammed.

"Hannibal got his elephants from the forests which then existed in Tunisia. The area around Tripoli was forested, and the land surrounding it was able to support a population of six million at the time of Mohammed. By 1935, the population of Tripoli had dwindled to 35,000 and the country surrounding it was largely barren."

From a variety of old sources including W. W. Kellogg, W. C. Lowdermilk, J. L. Cloudsley-Thompson, and I. B. Blake.

The Romans imported their grain from Egypt, Gaul and North Africa.
Julius Caesar and the Emperor Claudius built the port of Ostia for that purpose, the Tiber being too small.

Egypt and France remain productive in agriculture, though Egypt suffers from salinization due to the Aswan Dam.
North Africa fell under the control of their inveterate enemies, the Vandals in 430 AD, who filled the Mediterranean with pirates and Egypt fed the Eastern Empire until the Persians conquered it in 620 AD and permanently in 641 AD when the Arabs conquered it.
Likewise, the Visgoths occupied Gaul in 412.

The sources of grain supply were cut off.

At the time of the sack of Rome in 410 there were probably 1 million people in Rome which indicates their agricultural transport network was still working adequately. The city was forced to surrender because of a lack of any food.

The Goths beat the Romans at Adrianople in 378 so we aren't talking about many decades of Roman collapse due to alleged soil depletion.

Majorian, excuse me, but Rome is not the same thing as "the Romans" in general. There was a well organized transportation system that went from Egypt and North Africa to Rome by saling ships. But that was almost exclusively made to feed the capital. The rest of the empire had to do with local resources - most cities, for instance, didn't have the kind of harbor facilities and river transportation that served Rome. So, Namatianus tells us of silted harbors in early 5th century, not many years after Adrianopolis and it must have been something that had started much earlier.

Majorian, excuse me, but Rome is not the same thing as "the Romans" in general. There was a well organized transportation system that went from Egypt and North Africa to Rome by saling ships. But that was almost exclusively made to feed the capital. The rest of the empire had to do with local resources - most cities, for instance, didn't have the kind of harbor facilities and river transportation that served Rome. So, Namatianus tells us of silted harbors in early 5th century, not many years after Adrianopolis and it must have been something that had started much earlier.

At the time of the sack of Rome in 410 there were probably 1 million people in Rome which indicates their agricultural transport network was still working adequately.

And it wasn't until 1700 that another city reached 1 million, London (there is a possibility Baghdad did in 1100-1200, but it seems unlikely).
So buckle up campers, it will be a fun ride!

Indeed. The grain transportation system from Egypt to Rome kept working up to the last years of the Empire. It was not unlike our system of tankers that bring oil from Middle East Then as now, it was (is) a tremendous drain of resources, most likely a powerful co-factor in the collapse that was (it is to be).

The Nile failed to flood for 8 years from 1073-1064 BCE, leading to reports of cannibalism during that time period.

Hi,
Airdale the in again/out again farmer/clod/redneck/hayseed......ettccc

About 3 days ago I got tired of traveling to bookstores in search of good reading material.

I realized that if I purchased a Kindle I could order same books at less than half price and get them downloaded free via Amazon's Whispernet via EDGE(latest and very fast celltower protocol).

And so I did and promptly ordered a few good fiction books to read in my bed ,as I do a lot in winter.

Seeing this title (Dirt....) surfed over to Amazon Kindle Store and right away purchased it and another I saw on the same subject (Life in the Soil,James Nardi).

I am well pleased with the Kindle device. I can store and enormous quanity of books on it and read anywhere I desire to. I can always get a quality signal and the downloads are extremely fast. The account management is tops as well.

The battery life is days and days. It can also do web browing(rudimentary) and handle blogs as well as newpapers and magazines.

Now I can carry a very small thin Ebook reader with me in my coat pocket and pull it out any time and go back to my last Bookmark to continue reading.

Also when events to come cause many power outages I can recharge the battery by using a very low cost PV panel or even my auto. Also via a USB port.

This is one way I can prepare for the powerdown of the future. I intend to also purchase the Kindle DX as well and be doubly prepared to have backup and be able to keep all my survival data for the future. If I live that long of course.

I highly recommend the Kindle based on my experience so far.

Tonite I will be reading the above title at a cost of 7 or so dollars , perhaps $9.99 but it saves my fuel for a trip to the bookstore many miles away and keeps me here on the farm where I would rather be.

Airdale-its my desire to ONLY post when I have something worthy to add and this is my 'gift' to the rest here who need to build a 'library' and perhaps have it last

Airdale, Oh Worthy One. Thanks for the info on the Kindle. This is something I've been thinking about. I am a big fan of old fashioned books, but space limitations and the time/cost involved can be an issue. I also have a problem with loaning books that don't get returned. I'll need to wait 'til the price comes down some (or pray for a windfall of some sort). Is the DX a backup drive? I assume that you can't backup to just any usb drive.

The Kindle DX end of the USB cable is proprietary. You can plug the other end into a PC and it shows up as a USB drive. Stuff that you've purchased from Amazon really doesn't need backing up, if you delete the stuff a pointer to it goes into an archive and you can pull it back off Amazon later. A lot of the stuff on Gutenberg is in mobi format now so you can read them on a Kindle, you just drag and drop to a Documents folder and they show up on your list of stuff, or you can pull stuff off of it. The books purchased from Amazon navigate better though than the mobi texts at Gutenberg -- lots of old classics on Gutenberg though.

It will spoil you, I saw a favorable comment on the TOD about Greer's "The Echotechnic Future", two minutes later I was reading it -- they make it easy to browse available titles for the Kindle.

The browser isn't very robust and crashes a good bit, best to stick mostly to pages intended for mobile devices. The wireless drains the batteries considerably faster when turned on. No backlighting, its electronic ink. Power consumption is low, it will stay charged six or seven days with the wireless off.

Thanks, barrett. I have a few more questions, but Leanan made a request on another thread for us to try and stay on topic more. I'll do some research.

Fortunately we have a good library system here (King County, WA). Not only do they have a fairly large selection - they will get the books you want on inter-library loan if they don't have it. I've read books that are not even in print (let alone Amazon).

http://www.kcls.org/

thanks airdale. I been look at one of these new contraptions for a while now. got a friend with one and he echos your recommendations. Think i will borrow his for a day or so and try it out.

Incidentally, this post and many of the comments below include recommendations of many publications for how the manage the land and soils. Being from your generation I am familiar with some much more dated information on these subjects. One of the best of these publications was published in 1936 and includes information on one of the most important aspects of land husbandry. It deals with the management of the Little Waters, The document was produced by the old Soil Conservation Service and one my grand father referred too often. Here is the site for this old very valuable document. Can this sort of document be saved on a Kindle?

http://www.biodiversitylibrary.org/item/59519#36

Rube,

Yes,,just d/l to your PC and thence via usb to Kindle.

There are some websites where finding free books to put on Kindle is discussed in detail. I deleted mine so can't recall it.

Even private text docments on your PC can be placed on Kindle and perhaps other file types as well.

Good luck

Airdale

Kindle version can be found here,
http://www.archive.org/details/littlewatersstud00persrich

You can sort of testdrive a kindle with the PC version

http://www.amazon.com/gp/kindle/pc/download

I hear ya Airdale. My farm is 50 miles from nearest city.
Love my Kindle. Best thing I've bought in a long time.
The design is outstanding, reads just like a book. Highly reccomend.
Read Jared Diamond's "Collapse" recently, will now download "Dirt."

During my childhood in Amarillo Texas I had a young friend and neighbor whose father H.H. Finnell, I later learned, was an important dust bowl scientist. His papers are at OSU, the same school that gave Boone Pickens a geology degree. I have lost track of the Finnell family. As I recall my friend also had three older brothers, male triplets. I was fascinated with Mr Finnell's stamp collection. Should I ever have reason to be in Stillwater OK I would love to review these documents.
---One of my very earliest childhood memories is being stuck in a black duster during a Sunday drive in our Hudson/Terraplane.

http://www.library.okstate.edu/scua/collect/finnell/index.htm

http://www.perryton.com/black.htm

Robert
Very interesting subject, and Ugo has raised a fundamental point.
I can highly recommend this book (below) as a scholarly review.
My guest post of last year on ToD http://www.theoildrum.com/node/5182 used the quote below.
(I commented apropos soil fertility): ... it is not just the calories and protein that are shipped to the cities. The soil nutrients are also shipped to the cities, depriving the soil of nutrients needed to maintain its fertility. In the book On the Great Plains, we read that the 1000 year accumulation of soil nutrients was quickly spent:

They applied manure as it was available, rotated legumes when it was convenient. But they had no strategy for the very long term. By the 1930s, Rooks County fields had been planted, cultivated, and harvested sixty times without rest. Soil nitrogen was about half what it had been at sod-breaking and crop yields declined steadily. And now no western frontier remained. From the vantage of 1930s, crop agriculture in Kansas does not appear very sustainable. All the arable land in Rooks County - and in the nation for that matter – had been identified and plowed. Soil nitrogen and organic carbon drifted steadily downward, and with them yields and profits. Faced with this dilemma, farmers implemented a dramatic innovation in soil nutrient management. Rather than adopt one or more of the ancient strategies, farmers (and the industrial nation behind them) created a new option. They appropriated abundant cheap fossil-fuel energy to import enormous amounts of synthetically manufactured nitrogen onto their fields. …” page 219, ‘On the Great Plains: Agriculture and Environment’, Cunfer 2005; preview in googlebooks

I gather from Cunfer that the 'dust' episodes were quite complex, but related mostly to drought.
Clearly, though, in modern times industrial city cultures have demanded more from supporting agriculture than even Rome did in its day.

Phil

And this was part of an ecosystem that supported 60 million buffalo, sequestered carbon, and added to the top soil, still delivering millions of pounds of nutrient dense food annually.
Grains are one way street to disaster, demanding biocide and ethnic cleansing of the environment, destroying topsoil, aquifers, and poisoning the oceans and water ways with toxic runoff.
Buffalo commons anyone?

60 million buffalo -- check out Dale Lott's excellent book "American Bison." He says this figure, which everyone cites, is greatly exaggerated, the maximum carrying capacity of the range was less than half this.

Keith

"It is fragile; is easily washed to the sea by rain."

Only if you live by the shore. Most eroded soil piles up in interior lowlands.

When I was in university, I took a few soil science courses. One of them had a class project whereby we calculated rates of erosion on our farms based on topography and cropping practices. My calculations showed that our cattle should have been scratching lichen off exposed bedrock but in actual fact we had about 20 cm of chernozem topsoil throughout and good grass. I showed this to my professor, who was good enough to say that obviously the formulas were wrong. My personal observation was that eroded soil never went far.

Since my day back on the ranch, most farmers in western Canada have switched to no-till crop production, where the crop is seeded directly into last year's stubble, and herbicides are used to control weeds, not duckfoot cultivators or Noble blades. To yank this discussion back onto Peak Oil, no-till cultivation obviously depends heavily on pesticides and tractor diesel, so future farmers will be faced with difficulties.

"no-till cultivation obviously depends heavily on pesticides and tractor diesel, so future farmers will be faced with difficulties."
- only large scale agriculture...

What you're leaving out is the mass of labor required to replace the equipment and chemicals.

What you're leaving out is the mass of labor required to replace the equipment and chemicals.

That would be horses, mules and oxen, of course. That would be sustainable b/c we would use their excrement as fertilizer. OTOH, mankind is too prissy to use human dung as a fertilizer [for the most part... I know more than one or two TODers who would use it, including yours truly]. Plus, human labor is too weak and wimpy. Nope. We'll have horses for sure! My grandaughter will be thrilled!

Craig

Dale, you may be correct in saying that it depends on where. But - just as a personal note - I can give an example. I was in Morocco a couple of years ago. It was winter; it was raining and the rivers were all dark red; the same color of Moroccan soil. It was soil being carried to the sea and lost forever. It was impressive.

Then I traveled to the Atlas mountains and - gosh - that was like the Moon: stripped bare of everything; trees and soil. It was all nude rock. But, in the past, there must have been trees there. Deforestation is most likely the cause of the disaster. In some valleys, however, the Moroccan farmers do manage to keep topsoil and cultivate something. I don't know how they do that; possibly they exploit the local orography.

The problem is cultivate is being misused. We should cultivate like we make bread, instead of till and rake and dig and let blow away.

Dig a hole for a tree, cover and mulch. Don't plow and plant and spray.
Put a hole in, plant and mulch and let grow, try to leave no bare ground, it only wastes it to sun, wind and rain.

Charles.

Another excellent, easily read book with a similar message is:

Out of the Earth: Civilization and the Life of the Soil
Daniel Hillel

A soil scientist, he has authored other books such as Introduction to Environmental Soil Physics, Environmental Soil Physics: Fundamentals, Applications, and Environmental Considerations and Soil in the Environment: Crucible of Terrestrial Life

[Edit Added - his publications]

From wikiquote:

“... the Latin name for man, homo, derived from humus, the stuff of life in the soil.” ~ Dr. Daniel Hillel
“Detachment has bred ignorance and out of ignorance comes the delusion that our civilisation has risen above nature and has set itself free of its constraints.” ~ Dr. Daniel Hillel (2004)

A web bio: "Daniel Hillel is professor emeritus of plant, soil and environmental sciences at the University of Massachusetts, Amherst. A renowned environmental scientist and hydrologist, he has worked throughout the Middle East, as a consultant to the governments of Israel, Pakistan, the Sudan, Iran, Egypt, Cyprus, and elsewhere; and as an advisor to the World Bank and various U.N. agencies. He has published over 200 scientific papers and reports, as well as popular articles in Natural History Magazine and the National Geographic Society's Research and Exploration. His nineteen books include definitive texts on arid zone ecology, irrigation, and soil physics, as well as the award-winning Out of the Earth: Civilization and the Life of the Soil, Negev: Land, Water and the Life in a Desert Environment, and Rivers of Eden: The Struggle for Water and the Quest for Peace in the Middle East."

Ugo

I did not (yet) read the book.

You write: "...the text becomes somewhat ideological when Montgomery tackles fields which are not his: peak oil, energy, and the economy. The result is that the discussion becomes shallow..."

This seems logic to me, however, in theory, a researcher should be able to write about anything he likes with sufficient profoundness. Sufficient means that he has understood the subject enough to draw his conclusions and stand before a jury of masters of each subject he treats in his work (provided the masters will not ask questions, which are not related to his work). The problem I see is that all studies about peak oil, energy, economy and society are interdisciplinairy. No one is a real master in these subjects and when one begins to write, he must oscillate between different subjects.

When should someone consider hisself mature enough to avoid such conclusions as yours? There is no degree in peak oil... Montgomery maybe could have written a perfect last chapter, he did not lack knowledge but stopped reasoning and lost himself in ideology?

Just a thought that I had, maybe not so important...

-Snomm

Well, you may be right, Snomm. Perhaps I was too quick in dismissing this section of the book. The point I should have made more clear is that I was completely absorbed by the book up to a certain point - then the spell was broken. The last chapters were too long and - it seemed to me - poorly organized. I didn't mean to slight Montgomery from the height of peak oil expertise, of course!

The egyptian empire lasted so long, because the annual nile flood regenerated their soil. Part of the Roman collapse was the importation of silk from china, at a 1:1wt ratio, silver to silk.

While not exactly about soil erosion this article by Gene Lodgson posted on the Energy Bulletin is relevant - he calls it impossible farming

http://www.energybulletin.net/51554

He discusses all the problems created by the need to dry corn.

Also there has been previous discussion on this site about Vomitoxin in wet corn - his comments below
blockquote>In corn country, a strange word is on the lips of all farmers these days. Vomitoxin. The wet weather caused an outbreak of moldy corn, especially a disease called Gibberella corn ear rot. The rot produces vomitoxin, which is toxic to both humans and animals. So even though we enjoyed high corn yields in 2009, some of the crop, after finally getting harvested at enormous cost, is not fit to feed. If vomitoxin is discovered in the stored corn, there is no fungicide that can contain it say the experts. Hog and livestock feeders are scrambling to find clean corn to feed. Even for ethanol, corn with more than 7 parts per million vomitoxin is not being accepted.

One corn grower who is also a knowledgeable seed dealer, tells me a strange theory. Corn does not usually get infected with this kind of Gibberella rot. He is convinced that the new genetically-engineered corn varieties won’t mature and dry down the way more natural corn varieties do and that is one reason we have such a wet corn problem this year. If this story gains traction, I can hear Monsanto howling in protest. But what if it is true?

I don't think we have the last word on the 2009 harvest...

I just finished reading Enriching the Earth: Firtz Haber, Carl Bosch and the Transformation of World Food Production by Vaclav Smil. This is a great book, but the parts about the chemistry and chemical engineering of ammonia synthesis are technical.

The Haber-Bosch process is still used today, 100 years after the first demonstration plant, although the process is greatly scaled up and much more energy efficient. Haber-Bosch allowed the world to grow an adequate amount of food for the first time in history, if food were evenly distributed.

The book was very encouraging to me at first, but I noticed a problem toward the end: Nitrogen fertilizer is being applied well beyond the optimum response rate, meaning that we are pushing agriculture to teh extremes made possible even with synthetic fertilizer. While over use is not occurring on average in the USA, China and some other Asian countries are applying twice as much just to get a little extra yield.

Figure 10.2 that shows nitrogen application and world wide food production have traced out a classic S curves, meaning that unless there are changes in the mixture of crops grown or some breakthrough technology, we are close to maximum production, the exception being sub-Saharan Africa where almost no fertilizer is used.

A good work on the subject is

Dale, Tom, and Vernon Gill Carter. Topsoil and Civilization. Norman, Oklahoma: University of Oklahoma Press, 1955. OUT OF PRINT (may be copied)
Remarkable survey of world history, showing that everwhere that civilization developed, it collapsed within 1,000 to 1,500 years, inevitably due to soil erosion in its watershed. The only civilizations so far impervious to this were Nile and Ganges valley, and China. PDF made.

Which can be downloaded from the Soil and Health Library hosted by Steve Solomon in the Agricultural Library section
http://www.soilandhealth.org/RealBookList.aspx

Last but not least: Again, no mention of re-mineralization of the soil. Do a search-be amazed. Type in Azomite.

Recently we had a well drilled, mostly through granite. Lots of rock dust produced in the process. Having heard of re-mineralization I put it throughout my garden. It did seem to have positive results. May not be the best rock dust to use, but it was there as a waste product of the drilling. Since many trees put down deep roots, leaves used as mulch or to make compost may have trace minerals as well. As far as nitrogen, urine is an easily collected source.

In my article “Peak Soil: Why Cellulosic and other Biofuels are Not Sustainable and a Threat to America’s National Security”, based on peer-reviewed scientific literature, it’s clear that the United States and other nations are not able to learn from history. Growing food crops for biofuels and using “biowaste” will only accelerate top soil, groundwater, forest and rainforest depletion, eutrophication of waterways, biodiversity loss, etc.
http://www.energyskeptic.com/Peak_Soil.htm

Biofuels also have a negative EROEI as Pimentel and Patzek have pointed out for years (as well as not being sustainable).

U.C.Berkeley scientists have been wise to concentrate more on the sustainability of biofuels than on EROEI, because EROEI can be endlessly debated about (i.e. boundary issues of which inputs to include, or when both sides agree on an input, if the value is too low or high).

Principles of Sustainability
Daniel M. Kammen Co-Director, Berkeley Institute of the Environment Energy and Resources Group , University of California, Berkeley
http://biomass.ucdavis.edu/materials/forums%20and%20workshops/f2008/1.1_...
Sustainability issues (direct/indirect):
Ecological:
• Energy security/greenhouse gas impacts
• Land erosion
• Pesticide and fertilizer run-off / eutrophication toxics
• Biodiversity/invasive species
• Water sustainability (total demand; irrigation; pollution)
• Soil conservation
Socio-economic:
• Food security and economics
• Displacement of indigenous people from land
• Environmental justice
• Labor law violations, particularly in other countries

Kammen points out in the presentation above, which is about much more than just biofuels, that “We are running out of atmosphere much faster than fossil fuels …”

Other articles:
Integrating Water Sustainability into the Low Carbon Fuel Standard Kevin Fingerman1*, Daniel Kammen1,2, and Michael O’Hare2 1 Energy & Resources Group 2 Goldman School of Public Policy University of California, Berkeley
http://rael.berkeley.edu/files/Fingerman_WaterSust.pdf
Slide show of “Water-use considerations for CA sustainable fuels”
http://www.energy.ca.gov/ab118/documents/2008-12-05_staff_meeting/presen...

Many of these sustainability of biofuels considerations have been incorporated by the State of California in its ghg emissions policies.

Hi:

Your article referenced above, "Peak Soil," is excellent and really shows the whole problem with using "biowaste." Ethanol is not just a waste of energy, it's a waste of soil, and thus worse than useless.

It might be worth the time to reformat the text at this link so that the text doesn't spread all across the page -- to make it more readable. I certainly hope that people will read it. Thanks for writing it.

Keith

It appears that, according to Montgomery, even "conservation agriculture" erodes the soil faster than it is being formed.

I looked at Montgomery's paper, "Soil Erosion and Agricultural Sustainability." This paper is also referenced by Jason Bradford who has posted stuff about agriculture on TOD, thus my interest. Bradford cites Figure 2, which gives results of soil erosion studies. Underneath this figure Montgomery states, "Shaded area represents range of USDA. T values (0.4 –1.0 mm/yr) were used to define tolerable soil loss."

The problem here is that these T values are about 10 times the rate of soil formation. In fact, Montgomery's own data seems to support this view -- see tables 1 and 2. David Pimentel, in his paper titled "Soil Erosion: A Food and Environmental Threat" (in "Environment, Development, and Sustainability (2006)") agrees; he gives a figure of 0.5 to 1.0 tons / hectare / year as the natural rate of soil formation (which translates to about 0.04 to 0.08 mm / year, I believe). This is an order of magnitude less than the T values which come to 5 - 12 tons / hectare / year. (Montgomery and Pimentel are citing some of the same people, in fact.)

What is alarming to me is that it appears that even "conservation agriculture" is eroding more soil, on average, than is being formed. If you look at Table 1 in Montgomery's paper, it looks like the mean values for conservation agriculture erosion (while much, much better than the erosion with conventional agriculture) is about 3 to 4 times the mean values for soil production. However, Table 2 gives a slightly more optimistic version of soil production, which would bring soil production almost about up to soil erosion under "conservation agriculture." (I don't understand the reason for the difference in figures for soil production in Table 1 and Table 2.)

Even if ecological consciousness permeates the globe, avoiding net soil erosion will be very difficult without leaving some land fallow. If we thought that, on average and giving it our best effort, in practical terms soil erosion was (say) three times soil formation, then it would seem to follow that we would need to set aside about three times the amount of land as fallow land than we have in cultivation at any time.

To me the obvious question is, why isn't this already a crisis? My guess is that (1) soil erosion proceeds very slowly, it has taken several centuries to destroy half the topsoil in the American Midwest, (2) until about 1700, human population and therefore agricultural needs was less than 10% of what it is today, (3) artificial fertilizers are masking the extent of the crisis. I know that we have a lot of other more pressing problems like the financial crisis, peak oil, global warming, and so forth, but it appears that soil erosion puts a fundamental upper limit on human population, and that even if everyone was vegan that population would need to be perhaps 1/3 of what it is today. This level of population is a figure which I believe on other occasions Pimentel has given as the likely future of human population.