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Synopsis:
One of the many various crises facing modern civilization is the fact that we need topsoil to grow crops, but the rains and the winds keep transporting it away from the farmlands. Something Must Be Done! I suggest that we go get it and bring it back! Also, due to where it went, it may
need to undergo some special processing, as in a factory, before it can be returned to the farmlands. So be it.
Details:
Anyone should be awed by the list of things that exist in topsoil, and which work together to make it qualify as topsoil. It is so chock-full of microbes and larger life-forms living in symbiosis that topsoil almost qualifies as an organism, all by itself. So, considering how important this stuff is to providing civilization with its food supply, you might think we should pay more attention to its care and handling than we do. Sure, some efforts are made to reduce natural soil erosion, but what about all those millenia during which it was thoroughly wasted? All those sand dunes in the deserts used to be topsoil, for example...
Gathering up sand-dune material, and trying to reconvert it to topsoil, is a daunting task. They call those things "sand dunes" for a reason! Worse, they are often far from where the farmlands are. And practically all the original organic matter that had been mixed with the sand has been digested over decades by ever-more-hardy bacteria, until it was gone. However, our civilization does have some good sources of large quantities of organic material, which might be given appropriate processing, including thorough mixing with the sand, and thereby let us create new topsoil. One of those sources of organics is called "yard waste": fallen leaves, mown grass, stuff left over from the farming/reaping season, etcetera. Left to itself, yard waste naturally tends to become part of topsoil, so let us copy that. And a second major source of organics is sewage. We process that stuff already, trying to make it safe enough for either disposal or usage as fertilizer. I say, "Take all that which is about to be be disposed, and mix it with the yard waste and the sand, add some appropriate bacteria and other life forms, and then wait for (encourage!) it to become new topsoil." YES, I know we will have to carefully extract certain toxic substances (mercury, cadmium, other stuff) before we can trust sewage as something from which to grow future food. Others know this, too, and necessary things usually do get done. Anyway, like fine wine, this may involve a storage facility (quite large!) in which aging occurs, but eventually as much good soil will come out as raw materials are fed in.
Next, there is water erosion of topsoil. In some ways this is easier to deal with than wind erosion, because we dredge rivers already to help shipping -- and much of the stuff we dredge is waterlogged topsoil. Many of the life forms in it have drowned, but the organic matter is still mostly intact. A much smaller storage facility for aging would be needed, when restoring dredged topsoil. YES, I know this has to be treated to remove pollutants, too! Other things that help this plan are the facts that the farmland from whence this topsoil came is right up the river, and that river transportation is one of the least expensive going. And, in many places there are extremely enormous quantities of former topsoil, waiting to be dredged! (There is so much that the polluted upper layer could be ignored and left alone.)
Have you ever seen a map of the the world's geography during the last Ice Age? Ocean levels were hundreds of feet lower than today, because so much ice was piled on top of the landscape. You should look for such a map, and note the rivers! ALL of them carved deep canyons as they flowed down those last few hundred feet toward the seas. Today, with the oceans at a high level and still rising, all of those canyons are filled in with former topsoil! (The most extreme case is the Nile River canyon, because there have been times when the Mediterranean Sea became completely landlocked and all dried up -- the Nile canyon, today full of former topsoil, is much deeper than mere hundreds of feet.) Remember, those canyons filled up well before modern civilization began polluting the rivers....
One of the more interesting types of huge quantities of topsoil can be found at the mouths of rivers. The sea may be salty, but this is not true of the immediate vicinity of a river mouth (the Amazon pours such vast quantities of fresh water into the Atlantic that (in the appropriate area) you can be completely out of sight of the continent of South America, dip a bucket overboard, and drink the water). That means the topsoil in river deltas is basically salt-free, and can be reclaimed. So, for example, in the United States, most of Louisiana could be dug up out of the Caribbean Sea, and spread across the remaining states as topsoil. :)
Using human waste as fertiliser.
http://www.tve.org/ho/doc.cfm?aid=573
[squeak, Oct 04 2004]
[link]
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Is this an idea or an eco lesson? it would seem to me this is already baked by ecologists |
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Not on a large industrial scale, though. |
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The deltas at the mouths of rivers seem like a good place to start. After that, why not dredge the seafloor? Plenty of dirt there (bottom soil?). |
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phoenix, the seafloor will be salt-enriched. Otherwise, I'd agree. |
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Most of the dredging around here counts as toxic waste... |
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This idea seems to have two parts:
1: Composting on large scales.
2: Use of dredged materials as soil. |
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Many municipalities already have large scale composting for yard waste. Feedlot animal waste is also routinely added to fields. So this part looks baked to me. |
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The part about adding dredged materials to soil I am less sure about. I think this is also routinely done, at least in freshwater dredge operations. |
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Only references I could find were to covering piles of dredgings with topsoil. |
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Do you even need sand to make a growing medium, which let's face it topsoil is? Why can't we use said bacteria and nutrients and mix it with recycled plastic pellets or rubber or something? Humans are sending millions of tonnes of waste to landfill let's turn it (at least the non toxic stuff) into top soil (land fill but on a broader and shallower basis?) |
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Peticelli, while much of topsoil is organic, it does have a significant mineral component, often a mixture of clay and sand. When the soil dries out and wind erosion sets in, the clay is abraded into dust, and the sand grains also join the breeze (probably helping to abrade the clay). It bothers me a bit that there are so few "dust dunes" out there, to add to the sand when attempting to recreate topsoil (any dust dunes would turn to mud at the first rainfall, while sand dunes are mostly unaffected by modest rains. Well, there ARE dry lake beds which are also mud flats, so perhaps we can get the clayish component from there. |
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Not all farmland has lost it's topsoil over the centuries. That happens to badly managed crop farmland, overgrazed animal farmland and badly managed forests. In Kent (south England) for example, they are crop farmers and have been for a veeery long time (Kent is known as "the garden of england" and still produces huge amounts of fruit and veg). The country lanes and roads down there are lower than the farmland around them. Sometimes up to 6 or 7 feet lower. This ancient farmland has been well managed and now has extremely thick topsoil. |
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You don't need to add bacteria and other life forms to compost. They get in there themselves. Rotting (composting) does not need to be encouraged either. It happens naturally.
I agree that composting should be carried out on a larger scale than present but this idea makes it sound unnecessarily complicated. |
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Using poo to improve topsoil is the process called dunging which has probably been going on as long as there have been farmers with animals and farmers growing crops. Animals eat plants, animals poo, put poo on land, grow more plants. |
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Using human waste as fertilizer is also well baked. Urine can be used directly because it is sterile. Poo needs to be treated to kill of the bacteria but this can easily be done by heating and drying. (link) |
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Dust doesn't form dunes because it's too light. That's what makes it dust. When the sand particles erode so much that they can be blown away, they become dust. |
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River silt is also well known to be fertile, which is why river valleys are so often farmed, but dredging of rivers or oceans can also be devastatingly damaging to aquatic and marine life. You effectively remove all the "underwater topsoil" along with all it's organisms which are essential parts in the food chain. |
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This whole thing is pretty badly researched. It's sensible content could be broken down to: |
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1. Manage farmland/forests better.
2. Compost organic waste and use it instead of sticking it in landfill.
3. Use more poo. |
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Erosion is a natural process. If you're trying to save farmland, better to mitigate than to run around afterward trying to gather it all up. Honestly, Vernon. What's next? Reverse the drought by catching all that evaporated water that's floating away? |
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squeak, your "breakdown" of this Idea it totally about managing existing farmland; you are completely ignoring the fact that there are vast areas of land that which have NOT been managed as well as in Kent. Those areas need replenishing, and the material needed to do that has to come from somewhere. It logically follows that to replenish large areas you need either long-term or large-scale processing. The global population pressure will not give us the luxury of taking our time, so large-scale processing is going to be needed. |
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Next, dust DOES form dunes...on Mars...but as you might expect, this is because the atmosphere there is so thin that winds there don't have the same force that they have on Earth. Also, dust is NOT entirely eroded sand grains. Some is, sure, but sand is largely fairly pure silicon dioxide, while clays are largely silicates (aluminum silicate, magnesium silicate, iron silicate, etc). Silicates hold most of the minerals that plants need, while sand mostly doesn't. Dust from silicates does need to be added into the mixture, when restoring topsoil. |
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Next, yes, I know that one could wait for bacteria to arrive at the natural rate and do their thing. This is again a matter of time versus need. Also, Nature offers enormous numbers of types of bacteria that we would rather not be growing in topsoil -- and just letting Nature take its course does not offer much in the way of guarantee that the most desirable types of bacteria will take the lead in establishing themselves, in our attempts to reconstruct lost topsoil. |
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Next, yes, I've known for years that, for example, farmers in China have been dumping human waste back into their fields for about as long as they have been farming in China. In the cities, though, some kind of stigma against human waste has joined the culture (possibly for the valid reason that cities were rather unhealthy places to live, also for millenia, mostly because of human waste). I sometimes wonder why there was no mindset about this notion: "Every farmer's cart carrying food to the city can also be a cart carrying waste from the city." (Appropriate cleaning needed between trips, of course.) Certainly that notion is about recycling organic matter on a large scale, just as a small farmer, who can mostly feed only his own family, would do on the small scale. Anyway, the current mindset in many cities is that human waste simply must be gotten-rid-of, and this is the mindset that needs to be changed. Your goings-on about it being done and works doesn't change the fact that it doesn't get done in all-too-many places -- and that often, those places are fed by farmland that is badly in need of topsoil. Large areas of farmland that need a large-scale fix, notice. |
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Finally, regarding river silt, you have managed to somhow take what I wrote about hundreds of feet of depth of river silt in various places, and transform that into dredging hundreds of kilometers of river LENGTH. Certainly I agree that the dredging YOU imply will be devastating to much river life, but **I** was indicating no need for that! You can dredge one kilometer of river in the right place, hundreds of feet deep, and get the same amount of dredgings as if you had devastated hundreds of kilometers of river, while actually only devastating one kilometer. Such trade-offs are tolerable, and equivalent ones happen all the time. |
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lintkeeper2, what you describe is the same as closing the barn door after the horse ran away. You also imply that there is no reason to go chase it down. Think again! |
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Topsoil is not so much a problem where proper farming techniques are used. A bigger problem is chemical fertilizers and antibiotics saturating the topsoil and runoff from farms. Dangerous bacteria grow stronger after generations of mutation in residual antibiotics (from say, cattle farm runnoff). Soil and rivers are destroyed by the residuals, making the soil unsuitable for crops and the water unsuitable for irrigation. If you did manage to mine the topsoil back from river deltas, it would contain all of the chemical residue that modern farming practices have introduced. |
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[bmadigan], that is a good point. However, topsoil has been flowing down rivers for far longer than the last century or so. That ugly stuff on top of the settled-out heap can be stripped off, to get at the really big deposits underneath. |
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If it is possible to get past the governmental regulations, the concept has the possibility being a profitable business. Dredging can be efficient using the same methods used to beef up shore lines, and barge transport by water (i.e., up the Mississippi) is inexpensive. |
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Also, dams have silt problems. Possible double dip opportunity? The dam pays for removal and you sell the soil... win-win. |
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Silting, erosion, and sedimentation provided much of the 'livable' flat land worldwide. Granted, it isn't all topsoil, but if you begin excavating hundreds of metres of subsoil you'd better prepare early for the consequences. The only sensible plan I know for conserving soil and advancing agriculture is to do what farmers have done for centuries on farms near the origin of soil high in mountainous areas of the world. Here (actually, there) farms are terraced and stepped up hillsides steeply, and that general model is followed as elevations decrease until natural water fills these terraces and creates rice paddies. |
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While I agree that soil production would be best done on a large scale through well-researched methods, what consequences follow some of the grander aspects of your thoughts, [Vernon]? In a sense, the erosion/sedimentation cycle is like a climate system. We fear what may come from changing weather trends, increasing ground temperature, terraspheric dehydration, groundwater salination, and rising levels of particulate airborne matter. Topsoil health is an indicator of our biosphere's health, but in a subtile way like chronological age is an indicator of human biological age. You're not giving many clues as to where you'd choose to begin dredging, or filling, and for that I'll have to (-) this idea generally until there are additional facts to consider. |
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If one begins pulling dirt out of rivers from the delta up, baselevel will change, most likely to a steeper gradient, causing more erosion than was present in the first place. |
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dungbeetle, actually a NARROWING of a river will do more to cause erosion than deepening it. Keep in mind that dredging is done because rivers drop some of the silt they carry, all along their lower lengths. Deepening via dredging can only speed the river if done all the way from the river's mouth. And that extra speed just means that the carried silt (NOT necessarily including extra eroded material) goes farther down the river before being dropped. |
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