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Permaculture Reflections

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“I love this plan! I’m excited to be a part of it! LET’S DO IT!”

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March 28, 2014 by Douglas Barnes Leave a Comment

Image of plan

An imperfect plan.

It may have worked for Dr. Venkman and the crew, but loving your plan is a great way to get yourself into a lot of trouble.

The permaculture design process starts with the creation of a clear and concise goal – something that elegantly answers the question “What are we trying to do here?” Your goal is what is distilled from asking why as many times as you can tolerate.

Once you settle on a goal, you enter in on the process of planning. You create a strategy whereby you try to achieve that goal. This is also a stage where you can get into a lot of trouble. One easy way to get into trouble is to fall in love with the plan you’ve created. You see, the problem is that a plan is just an idea. And let’s face it, a lot of ideas are just plain bad. Loving a bad idea makes reality your adversary, and you don’t want that. Trust me. Love for a bad plan will have you wasting energy and resources. It will sap your time, money and strength, only to leave you with disappointment.

Don’t panic. There is a way to avoid the pitfalls of love. Once you have crafted your goal to the point that it is a concise statement reflecting what you really want, you then set out to make “an imperfect plan.” Seriously, call it this, even if only to yourself. We all have imperfect knowledge and imperfect information. What can we hope to create from this? Imperfect plans. Acknowledge that the plan is imperfect. If you admit up front that it is imperfect, you won’t be hesitant to make changes in the face of conflicting feedback.

Filed Under: Article Tagged With: Design

When Swales Can Kill

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March 24, 2014 by Douglas Barnes 6 Comments

Sensationalist title, yes, but unfortunately swales can cause damage, or even loss of life. When designing and building earthworks, “Don’t kill people” should be your first rule. I’m going to highlight 3 situations in which these water-harvesting earthworks could be dangerous and perhaps even fatal.

Diagram of a swale

The swale is a water-harvesting ditch on contour.

You’ve Heard of Quicksand. How About Quick Clay?

When I get a call from a client who is east of me inquiring about earthworks, I immediately head for a soil map. The reason is that much of Eastern Ontario was covered by the Sea of Champlain around 10,000 years ago. Here silt, clay and organic matter were deposited in the sea’s saline environment, leaving a deposit of a particular kind of clay known as Leda clay, quickclay, or Sea of Champlain clay. The salt in the water acted as a cohesive agent. When the sea disappeared, this clay was then exposed to fresh water from rainfall, washing away much of the bonding properties of the salt, leaving the very unstable structure of the Leda clay.

Under pressure, or sometimes when highly saturated with water, Leda clay can liquefy – something which has triggered a number of landslides in Eastern Ontario. If you place a swale somewhere, you are going to make the ground downhill of the swale wetter. This creates conditions that could make the ground unstable, triggering a landslide.

So what do you do in this situation? I don’t have any set rules. I look at the need for swales and if other approaches would suffice. I also look at the slope and the likelihood that the land might slide. (Keep in mind that these slides can cover a lot of area and might start a long distance off site.)

In some situations, swales just might help prevent damage. Leda clay contracts a lot when dry, which can lead to foundation damage. If sliding is not a danger, you might help a building keeping the ground hydrated with swales. Personally, I’d look to preserve moisture with mulch and ground cover in those situations, just to be safe.

In short, Leda clay makes me nervous. I’ve yet to install or recommend any swales in these situations. If you’ve had any experience dealing with quick clay, I’d love to hear about it in the comments, or via the contact form.

Video by Christian Olsen.

Trouble in Paradise

Swales can trigger landslides in tropical highlands. These hilly areas get tremendous volumes of rainfall. Forcing more water into hillside soils in these regions can trigger a slide, even when they are forested. Consider the following passage from Jared Diamond’s Collapse:

Landslide

Image of tropical highland landslide by Radhakrishnansk

[O]ne European agricultural advisor was horrified to notice that a New Guinean sweet potato garden on a steep slope in a wet area had vertical drainage ditches running straight down the slope. He convinced the villagers to correct their awful mistake, and instead to put in drains running horizontally along contours, according to good European practices. Awed by him, the villages reoriented their drains, with the result that water built up behind the drains, and in the next heavy rains, a landslide carried the entire garden down the slope in the river below.

These are areas of 3 or more metres of rainfall a year. There’s no problem with available water in these regions. Don’t risks potentially deadly landslides by floating mountainsides with swales.

Swales to Stop a Leaky Basement? No

As mentioned above, swales make the area downhill of the swale wetter. I had someone near the waterfront in Toronto contact me a few years back about doing some work on her property. Her house was at the bottom of a bluff, and she was wondering about swales above her home to keep the water out of her basement in the spring. In this situation, there was the increased risk of sliding, as well as a good guarantee that spring flooding would be made much worse. Sometimes the best advice is not to do anything. I was happy not to ruin her home with swales and I suggested some drainage to carry water away from the uphill side of the home.

Filed Under: Article Tagged With: earthworks

How to Build Tropical Soils

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July 1, 2013 by Douglas Barnes Leave a Comment

Building Tropical Soils from Douglas Barnes on Vimeo.

This video looks at building soils in dry and humid tropics, as well as desert regions. The footage is from Andhra Pradesh, India in 2009, and the Loreto Region of Peru in 2013.

For more on the Chaikuni Institute, click here.

Mulching fruit trees

Mulching fruit trees in semi-arid AP, India

Filed Under: Article Tagged With: Tropical climate

2013 Guelph Organic Conference

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February 2, 2013 by Douglas Barnes Leave a Comment

The following is a write-up of my February 1 presentation at the Guelph Organic Conference. Many thanks to the event organizers and staff, my fellow panellists, and most importantly to the wonderful, engaging audience.

Permaculture Earthworks

University of Guelph

We are fortunate to live in a climate that is relatively abundant in water. The disastrous drought of 2012, however, shows us that we can no longer afford to take water for granted. Globally, nearly half of all land is arid, with a further 25% threatened with desertification. That’s the bad news.

I’m here to tell you the good news. I’m here to tell you about how, with a fraction of the time and energy we have spent degrading our environment, we can foster life and increase biodiversity. And we can do it profitably.

Let me jump right into the “how.” The “how” is based on a few design strategies. One of those strategies is to hold onto the resources we have on site as long as possible. In the case of water, we hold onto it in two ways. One is to put it through as many duties as possible before it is lost to us. The approach we are focusing on today, however, is to capture the water arriving on site, and take it over the longest, and slowest path practical.

Putting this approach into practice means starting at the highest elevation on a site and working downhill with the techniques I am about to highlight.

To hold water at the top of a site, we typically forest hilltops and ridges, along with steep slopes. Forests are very effective at capturing water with minimal runoff. They also have the added benefits of preventing erosion, and adding fertility to the top of a site where it can naturally flow downward. This is a strategy hit on by the Japanese in a traditional mountain region farming system they call Satoyama. Admittedly, this is not a form of earthworks, but it is so integral to water harvesting design that I would be remiss not to mention it.

Water harvesting earthworks have the goal of intercepting runoff water, and storing it. The simplest of the interception techniques involves patterned ripping of the soil with a subsoil plow, given the right soil conditions. With the plow, we cut narrow furrows into the ground just slightly off contour to capture runoff and gently direct it from wetter areas to drier ones. Originating in Australia, this technique has proven very effective there.

This type of interception technique is also really a storage technique as well. The ground is a fantastic place to store water. There it is largely free from evaporation while being available to plant and soil life.

Another common interception technique is the swale, which is a water harvesting ditch dug level on contour. It stops water flowing downhill, allowing it to sink into the ground.

This is a good point to address an argument that too often comes up around water harvesting. Sometimes you will hear a claim from downhill people that you are “stealing their water.” Nothing could be further from the truth. They might see a temporary reduction in runoff onto their land as you hold onto more of your water, but, as you recharge the water table, the medium and long term effect will be to increase the local ground water. In many cases, ephemeral streams will start to have a more regular or even constant flow.

Both of these interception and infiltration techniques are inexpensive and cost effective to install.

Swales are also used in conjunction with earthen dams and ponds. The dams we are talking about are small reservoirs sealed with clay, not concrete structures. Both ponds and dams provide water for irrigation. They can also be put to productive use through aquaculture. While our climate does not support a very large variety of productive aquatic crops, warmer climates can produce prodigious quantities of edible and palatable plants. And even in our climate, water has a better feed conversion rate than terrestrial livestock. For instance, it generally takes 870 grams of feed to produce 100 grams of beef, or 190 g of feed to produce 100 g of chicken. The feed conversion rate for fish, however, is typically 120 g of feed to 100 g of fish.

Aquatic systems are also excellent producers of soil. Their periodic need for dredging yields a very valuable product that adds to site fertility.

In semi-arid and arid conditions, we sometimes employ a land imprinter – essentially a large, patterned drum which can break through desert hard pan and leave divots in the earth. Here debris, including seeds, will collect and moisture will concentrate during rains. This simple approach has proven effective in re-establishing grasslands.

Dug pits can work similarly to establish drought-hardy trees in semi arid conditions.

This has been a very rapid summary to give you a taste of some of the techniques we use. I’d like to leave you with a brief case study of the most dramatic work I have been involved in.

In 2009, I received an invitation to carry out a joint project with a local NGOin Andhra Pradesh, India. This region had traditionally had a dry tropical climate. In recent decades, however, it has grown increasingly arid at an accelerating pace.

When I finally arrived, I found the situation on the ground to be quite bleak. The vegetation is starting to give way to cacti and other desert xerophytes. The local village I worked in now has to draw water from a well over 1000 feet deep, the water from which is tainted with excessive amounts of naturally occurring fluoride.

Before leaving, I’d had it in mind to employ a number of techniques, including ripping the ground with a subsoiler, and building a dam. The soil conditions only lent themselves to swales, however.

I was given carte blanche over 7acres of arid hillside that a local mango farmer considered a write-off for everything except a seasonal crop of pigeon peas.

After crunching some formulas, we laid out contour lines on three levels, then excavated over 400 metres of swales, capable of holding over 1 million litres of water.  Our host farmer was initially dismayed to see us chewing his land up, but started to get the gist of what we were doing. The night before we were to complete the project, a pre-monsoon storm hit, so when the rains hit, he took off on his motorbike, and headed to the site. He was delighted to see that all the water that would have washed down the hillside, and eventually out to sea, was now stored in the ground.

Before I left, I made what I thought was a bold prediction. I said that within 3 years time, there would be springs appearing at the bottom of the hill during the monsoon season. It turns out that my predictions were very conservative.

Six months after I left, I received a photo update of the site. In it, I saw that they had established mango seedlings, and they had managed to do it without drip irrigation – something very unusual even on flat sites in the area.

Tamarind trees on the opposite side of the valley had a very anemic crop, whereas a tamarind tree adjacent to the swales produced an unusually bountiful crop.

I’d made my bold predictions of springs appearing within 3 years. At the bottom of the site there had been a well with water 3 metres down while I was there. Now six months later, the well was full. Water is no longer an issue on the site. And what had been a meager pigeon pea field is now a lucrative mango polyculture.

The results were beyond my most optimistic expectations, and the cost of the immediate project was just $650 Canadian. This is really a prime example of how the cost, effort and time it takes to repair a site is far less than that required to destroy it in the first place. As soon as we pattern our actions in harmony with nature, the payoff is immediate.

These techniques have proven effective everywhere from arid desert to tropical rainforest. They help to rejuvenate drylands, and buffer against drought. We can expect increasingly erratic weather in our future, including severe drought. These water harvesting approaches can help us through the rough times to come, and they can replenish our water tables during the good years.

Filed Under: Article Tagged With: earthworks

Tilia americana

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October 19, 2012 by Douglas Barnes Leave a Comment

Thanks to a student of mine, Tom Marcantonio, I gained an appreciation of this common temperate North American tree. Tom had learned of the use of its inner bark for cordage, and was using stakes, and cordage made from the tree to support his plants.

Tilia americana, flowers

Tilia americana, flowers.
Image by Tie Guy II.

Tilia americana, also known as Basswood, and American Linden, is hardy in USDA zones 3 to 8, making it a common feature on the landscape. It does well on deep, well-drained soils, but it can handle dry or heavy soils. Left alone, it could grow to 21 meters (70 feet).

Its a useful winter browse for deer, and its buds are food for birds. The summer fruits are eaten by birds, squirrels, and mice. Older trees tend to rot out in the center, leaving habitat for animals. Its nectar makes it a good bee fodder. However, it does have the tendency to attract pests; among these are borers, aphids, leafminers, scale, and Japanese beetles. As we say, however, the problem is the solution. This tendency might make it a useful tool in a push-pull integrated pest management regime. If anyone has tried this, please let us know how it went.

The soft wood does not splinter easily, making it a good wood for carving. Its ability to coppice makes it all the more appealing. To make cord, soak branches, then peel off the bark. The inner bark is the part then made into cord.

The sap has traditionally been boiled to make syrup, or taken as a drink. Young leaves can be cooked and eaten as well.  The nuts and flowers can be ground into a paste that is said to have a chocolate taste. I’d love to test the truth of this claim. The flowers can be put in salads, or brewed into a tea. I have seen one recommendation cautioning moderation in drinking the flower tea as it could cause heart damage. I think this warning stems from the β-Sitosterol it contains. For this reason, it is probably best for pregnant women to avoid altogether. The flowers do have a whole host of interesting chemicals in them, including but not limited to bioquercitrin, which helps regulates cell growth. Recent research suggests that T. americana can be used as an anti-anxiety treatment.

There are a few places I could use this tree on my site as part of a shelter belt. Though I have seen no mention of its use as a fodder tree, I would imagine it could be used as such. I suspect it would work well in a silvopasture setup.  Its many fine properties make it an appealing candidate that I am sure to utilize.

Filed Under: Article Tagged With: trees

Patterns in Nature: Waves and Spirals

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September 20, 2012 by Douglas Barnes Leave a Comment

Patterns In Nature: Waves and Spirals

The information here will be instructive regarding the functioning of the universe (of which the designer should have at least a rough grasp). It is useful when considering the temporal aspects of growth (i.e. how things grow over time), but is only marginally useful as a physical design template. It does, however, happen to be really fascinating.

In Bill Mollison’s Permaculture: A Designers’ Manual there is a passing reference to “Winfree’s ‘doped’ chemicals” that long ago caught my eye. The chemicals Arthur Winfree was working on were, in fact, the Belousov Zhabotinsky Reaction, which is what is known as a reaction-diffusion system. As we’ll see, such systems govern many of the biological and physical systems we see in nature.

Before we get too far ahead of ourselves, let’s start with Boris Belousov. Belousov was looking for clues on the glycolysis process (and happened to be on the right track, too). He found a reaction that would react, reverse, and repeat the process with a regular period.

In trying to get his research published, he was given the brush off by the establishment because, to the world of chemistry at that time, what he was claiming sounded akin to striking a match, then having the process reverse, then reignite, then reverse, and so on. All known reactions at the time settled linearly into an equilibrium state.

Later, Anatoly Zhabotinsky took a look at Belousov’s work, and expanded on it. The reaction the two scientists pioneered became known as the Belousov-Zhabotinsky reaction. The BZ Reaction is a catalytic reaction in which the catalyst forms out of the reactions own reactants. This autocatalysis burns out and meets with a different reaction that forms products needed to restart the autocatalysis once again.

In the reaction, travelling circular waves emerge and propagate outward. Should those waves happen to meet with an obstruction in the medium, they form spiral waves – something we will come back to several times in our explorations here. Describing it only goes so far. It’s better to see it for yourself.


Reaction-Diffusion in Nature

Reaction-diffusion systems also occur in nature – a lot. In a biological system, cells will start in a state susceptible to excitation. They become excited from the stimulus of neighbours, passing on the excited state. They then go into a period of recovery. This is embedded in the mathematical template governing the chemical automation that runs your body, other life forms, species interaction, and possibly galaxies, too.

Your heart operates this way, for instance. A wave propagates across your heart, giving the cells an instruction to beat. If it meet an obstruction – a damaged area of the heart – a spiral wave can form and propagate, as in the BZ reaction. This is what happens in ventricular fibrillation when one has a heart attack.

Image of ECG waves

From ScienceDirect.com

This same reaction-diffusion dynamic (excitation, spread, recovery) occurs in interacting species populations, as well. For instance, you see the waves temporally in pest populations in your garden. The pests appear, providing an untapped food source. Predator populations then respond with increased localized populations, reducing the initial wave of pests. The loss of food leads to a decline in predator population, allowing a recovery of the pest/prey population.

Similarly, you might also notice this model is at least prima fascia applicable to memetic social systems like propaganda, for example. True or false horror stories about the official enemy emerge, followed by outrage in the population with potentially deadly results, followed by a return to relative sanity. Repeat as necessary, nationality irrelevant. You might also imagine similar patterns emerging in economics, fashion, and so on.

Enter Chemotaxis

Let’s consider a bacterial population. One cell emits a chemoattractant that diffuses out into the medium it is in. Detecting this signal, neighbours are drawn in. The neighbours congregate where there is the greatest concentration of chemoattractant, resulting often in either circular waves, or spiral ones.

Dictyostelium discoideum

Spiral wave propagation looking in Dictyostelium discoideum looking very much like the BZ reaction. From metafysica.nl.

I’ve noticed the same pattern often emerges in mycelial propagation. Enter Paul Stamets who has noted the appearance of these patterns in his book Mycelium Running.

Nature tends to build on successes. The mycelial archetype can be seen throughout the universe: in the patterns of hurricanes, dark matter…. The similarity in form to mycelium may not be merely a coincidence. – Paul Stamets, Mycelium Running

Spiral shapes in fungi

Spiralling Psilocybe and Armillaria, respectively.

From Mycelium Running by Paul Stamets

I would say indeed it may not be. I would argue that these forms are mathematically predestined. (This is not to suggest, however, that hurricanes are the product of reaction-diffusion systems. They emerge out of fluid dynamics.)

Galaxies? Really? Come off it!

I had always only ever thought of galaxies coming about as a result of gravitational interactions. My education in physics being limited to undergrad studies, I did not encounter much in the way of astrophysics, unfortunately. As it turns out, the way I had envisioned galaxy formation to occur would, in fact, result in a galaxy that would quickly wind so tightly was to appear to be just a nondescript disc.

This problem of formation was mostly solved when Chia-Chiao Lin and Frank Shu proposed the Density Wave Theory, in which the density of the spiral arms of the galaxy prevents the galaxy from winding up into a disc.

It is a great theory, elegant, simple, plausible, and with backing evidence. But it doesn’t quite explain every type of spiral galaxy. Theoretical physicist Lee Smolin had a look at the problem of galaxies where the density wave doesn’t hold, and proposed a hypothesis whereby the galaxy was actually one great reaction-diffusion system. In his model, shockwaves from star formation and supernovas drive one reaction, and ultraviolet radiation from giant stars serves to inhibit it. The hypothesis isn’t perfect but just might explain some aspects of galaxy formation.

Now Available in 3D!

The BZ reaction shows a two dimensional expression of the propagation of travelling waves, or spirals, as the case may be. Taken in three dimensions, the travelling waves form expanding toroids, or, in the case of spirals, scroll rings. This form is reminiscent of the much talked about but perhaps sometimes misunderstood “core model” in permaculture (more on this in a future article).

spiralling toroidal form

Scroll ring. From riowight.

Take the example of a jet of fluid flowing forward into a medium. The leading edge thrusts forward, and friction at the sides slow it down, creating a mushroom shape. These edges often form spirals as the following image of a portion of a von Karman vortex street shows. Keep in mind, however, that this is a characteristic of fluid dynamics, and not the product of a reaction-diffusion system. I am including it for illustration purposes only. Remember, though, that the appearance of spirals in a reaction-diffusion system is a result of fluid dynamics. Hence the relevance.

von Karman vortex

Portion of a von Karman vortex street. From Nasa.gov.

So there you have it, spirals from wave propagation. Is there some great mystical universal something going on? I believe these patterns emerge because they must. They are the mathematically prescribed result of chemical interaction in space and time. Galaxies do not form giant portraits of Homer Simpson because that is not a mathematically possible outcome. Bacteria propagating in a uniform petri dish do not form interlaced nonagons because that is not a possible outcome. What you see is what you can get.

Filed Under: Article Tagged With: Design, Patterns

Patterns in Nature: Packing Them In

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September 9, 2012 by Douglas Barnes Leave a Comment

As promised, here is a brief look at some more interesting patterns we get from the properties of surfactants.

How can you tightly pack elements in a design without resorting to the familiar and troubled row agriculture? There just so happens to be a property of surfactants that can help provide a little inspiration for that problem.

Image of a micelle

Micelle

Currentprotocols.com

In the last pattern article, we looked at adhesion (like things being attracted to each other), and the polar/non-polar features of surfactants. We had considered the effect of surfactants on surface tension, but if we keep adding surfactants to a solution, the non-polar ends attract one another, and form spheres called micelles. The polar heads of the molecule – the ends which are attracted to water – are on the outside, and the non-polar ends are in the centre. If you keep on adding more surfactant, you will start to get long cylindrical micelles. It is here where things start to get really interesting, and really useful for us as designers. The micelles repel one another, meaning that they exert a force on each other. If you recall from the first article, applying force on a system decreases its symmetry, but increases its patterning. The repulsive force of micelle against micelle, forces the system to rearrange in such a way as to minimize the total energy.

The following image shows this process in action.

langmuir films

From The Self Made Tapestry: Pattern Formation in Nature by Philip Ball

In a and b, micelles form. Notice how the hexagonal array discussed in the previous article arises here. As more squeezing occurs, a different pattern emerges, shown in c. There is fairly efficient use of space at this point, enough so to put a similar pattern into a design. With further force, the highly structured pattern in d emerges.

Why would anyone go to all this trouble? While rows are easy to build, they are not without their problems. I have seen “eco-farms” with row planting with the rows running up and down the topography. Barring thoughtlessness, I presume the intent is to promote erosion. These non-linear patterns are less conductive to runoff. Straight rows also require a sizeable enough patch of land to accept their unnatural array. This is often unsuitable in tight areas, or the rocky areas so common in the Canadian Shield. Rows are also generally set up to accommodate cultivators, which are great if your intent is to damage the soil, and increase erosion. We aim to make soil healthier, however, not degrade it. Rows, too, tend to be planted in pest-smorgasbord fashion, with grouping of like plants together, making it easier for pests to travel from preferred plant to preferred plant.

One could use these more natural arrays either for non-linear rows or as pathways for keyhole bed layout. While it would be a bit much to strictly follow such a pattern, it does give us ideas for systems a little more imaginative, and adaptive to the landscape than straight rows.

Coming up next, we’ll start to look at waves and pulses. Stay tuned!

Filed Under: Article Tagged With: Design, Patterns

Patterns in Nature: Surface Tension

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September 4, 2012 by Douglas Barnes Leave a Comment

Why is a honeycomb hexagonal, and how can that help me? How can I make a curved tensile surface like a roof with minimum tension? How can you make a structure stronger yet lighter than reinforced concrete?

radiolarianStick around, I’ll answer these questions, increase your designer’s toolbox, and even tell you how to make one of these guys (radiolaria) on the left here.

In the previous article, I asked the reader to consider a spherical raindrop. Indeed, as long as external forces do not impose upon water – gravity, air friction, sides of a container, etc. – it takes a spherical shape. But why?

Water has cohesion, which is a fancy way of saying that it is attracted to itself. To look at it another way, it is sticky to itself. When was the last time you saw the ocean just spontaneously break apart from itself into individual small droplets or a vapour? Liquids just don’t do that. The internal forces – the positive and negative charges on either end of a water molecule – hold the water together.

Water strider

Surface tension has its practical applications.

Within the drop, there are attractive forces all around an individual molecule. On the surface, however, there are no atoms outside the drop to attract the surface atoms. This creates a tighter bond amongst the surface atoms, which in turn is what is responsible for surface tension. In water, the surface tension is strong enough that your friendly neighbourhood water strider is able to glide across the surface of water like some sort of Gerridae messiah.

surface tension

From
http://ga.water.usgs.gov

Because the surface molecules are all pulling equally around the entire surface of the droplet, it forms the only shape that equal force would allow, which is a sphere. As hard as you might try to push the droplet into a dodecahedron, as soon as you remove the force, it will snap back into a sphere.

You might wonder what all this has to do with honeybees. Don’t worry, I’m getting to that part. But first, we must look at bubbles. We’ve done half the work already, though. We can consider bubbles to just be anti-drops of water, only instead of water on the inside, we have water on the outside. The key is still the surface tension where air meets liquid.

And before we look at bubbles, we need to look at how they are made. Soap helps us make bubbles because soap molecules are amphiphiles ( meaning “likes both,” often called surfacants), which are molecules with a polar head and a non polar tail. The polar head is attracted to water, which is a polar molecule. The non-polar tail – which is the end sticking out on a bubble – is attracted to non-polar molecules like oil. This reduces the surface tension, which, counter-intuitively, perhaps, makes the bubble more resilient. (This property of being an amphiphile also lets us clean greasy dishes. The soap molecules are attracted to the oil at the non-polar end, surrounding them, and the polar end lets the water carry it.)

You’ve seen two bubbles meet before. They form a plane between them with the dividing bubble wall being just as thick as the wall of a single bubble. Even though two bubbles meet, the wall is not twice as thick. Maintaining that thickness would require more energy. Things naturally seek the lowest energy state, however, so the surplus soapy liquid distributes across the whole surface area of the two bubbles. They also join in a way that minimizes the surface area with respect to their internal pressure.

A light just went off in designer’s heads here. The bubbles form a stable shape with minimum use of material. And this is more than just interesting theory. This aspect of surface tension has been put into design as we shall soon see.

honeycomb shape

From http://originofintelligentlife.blogspot.ca/

On to the honeycomb! If we take three equal-sized bubbles and touch them together, they will meet with an angle of 120° between the walls. A honeycomb is made up of hexagons, with each point of the hexagon being the centre by which three hexagons touch. There are six points in a hexagon, and six such nexuses around each cell.

It just so happens that there are only three equal-sided shapes that will stack into a plane without leaving gaps: equilateral triangles, squares, and hexagons. Humans tend to like the square because it is simpler to understand. Nature, on the other hand, only knows the principle of minimum energy. So when it comes time to stack round things tightly nature makes the honeycomb rather than the side-by-side stacking in a case of beer (time to redesign beer cases). So when you want to maximize the use of space, for example when planting, you have to mimic the pattern in nature and use a hexagonal array.

Honeycomb pattern for planting

Hexagonal planting arrays. Some people are really serious about
getting them right. From
http://www.growbiointensive.org/

Going Deeper

p-surface

From 
http://www.currentprotocols.com/

Because of cohesion, the surfacants inside a solution can join together, and do so in some really interesting shapes. One of the shapes that can arise is what’s called the cubic P-phase. Because of the minimum energy principle, this is a shape whose surface tension holds it stable. The entire array is curved, but the total surface curvature adds up to zero.

We see this form when we take a  look at the skeleton of a sea urchin. This form is stronger than reenforced concrete, giving it promise as a design feature for structures where lightweight strength would be needed.

soap films

From
http://materialpraxis.files.wordpress.com/

It was the minimization of surface area that architect Frei Otto employed so many times. Otto would make wire frames (shown above) and cover them with a soap film to reveal the minimum shape. Then he would apply this to his design.

Now, I had promised to tell you how to make a radiolarian. Here’s what you don’t do. You don’t try to write some sophisticated genetic code (sorry  geneticists) to synthesize proteins that are going to construct these elaborate shapes… somehow. You just write a genetic code for a little guy to blow a foam of bubbles, then inject a mineral in a slurry and allow it to precipitate between the borders of the bubbles. Presto! Marine biologists everywhere will marvel at your intricate beauty!

For our next instalment, we’ll have a little look at an interesting property of surfactants that yields intricate, tightly packed, non-repeating patterns.

Filed Under: Article Tagged With: Design, Patterns

Water, Water, Nowhere

Posts in the Article Category at Permaculture Reflections, Page 3

September 3, 2012 by Douglas Barnes Leave a Comment

What a summer! Hot and dry, followed by hot and dry periods, interspersed with the promise of thunderstorms that bring furious, desiccating winds, and nothing else.

For a few reasons, there has been little activity on this site until this month. A large part of the reason for this is that I have been building a passive solar home by myself (big hat tip to my wife who helped hoist heavy things and who passed me tools at many critical moments).

Last summer we had a trench dug to hook us up with electrical power. While the backhoe was here, I got my earthmover to get a chinampa started. At that time, the water table was much higher, and when we dug deep enough, it was like a water main was burst. Water gushed into the chinampa.

But then we had a relatively dry winter with next to no spring run off. This turned into a rather dry May, which became a dry June, which became a parched July, followed by an arid August. Just a couple minutes walk from my door there are poplar trees in the ditch (those wet channels that run alongside roads) that are dead and dying from lack of water.

I had planned an earthworks seminar at our farm for July, but an inability to track down the equipment needed in time (namely a subsoiler) led me to cancel it for this year (sorry to all the folks who inquired). This is very unfortunate because we really could have used all the help we could get this summer.

The back end is the bottom of a ditch that holds water during wetter years. This year the water dried right to the bottom of the chinampa, about 130 cm down below the bottom of the ditch.

The water level in the chinampa grew lower and lower until all the water in one dried up, taking all the fish with it. Another one was down to a little wallow with a few surviving minnows and tadpoles. I dug a water hole in that one and gave the minnows and tadpoles a second chance, but without rain soon, that little hole will dry up, too.

Clearly, I will have to start putting into action some of the techniques I used in the more arid India. I am shocked at how bad things have gotten in one year. Mature trees are turning colours (some as early as July) because of the lack of rain, while temperatures remain about 3 to 5C higher than normal. If there has been one upside, it is that the lack of water has meant a lack of mosquitoes. But there is a lack of more other things, too. Dragon flies and damsel flies are missing in action, as are most of the other insects you would expect to see.

Happily, our garden has done rather well. Our beds are either hugelkultur beds, or heavily mulched beds, so when we water them, they stay moist for a long time. But the pasture looks rather disastrous. Lots of farmers in the area have had to cull herds due to a lack of hay, and the large round bales are selling as much as $45 higher than normal.

Doom and gloom. But what about answers?

Answers there are! There are subsoilers around, or so goes the rumour. Hitting our pasture with an intelligently applied subsoiler will allow more infiltration. It will also capture more of the snow melt that otherwise runs off the land. We can place swales across the pastures to allow more water to sink in, too. Planting up some pioneering trees will help with soil building, which will help with water retention, as well.

It seems the devastating droughts that climate modellers have been warning might have slipped over from future possibility to present reality. It’s time to start getting greedy with the water that hits this site.

Filed Under: Article Tagged With: Water

Senna siamea

Posts in the Article Category at Permaculture Reflections, Page 3

September 1, 2012 by Douglas Barnes 1 Comment

Cassia siamea

Gangi Setty of the Green Tree Foundation, and Dr. Kadir of the Rural Development Society show off Senna siamea in swales we built in 2009.

Though it is in the legume family, S. Siamea is not a nitrogen-fixing tree. It is a tropical plant not tolerating temperatures below 20°C well. It will establish in semiarid areas with rainfall as low as 500mm per year, provided there are droughts no longer than 4 to 6 months, and that the roots have access to groundwater. According to Jeff Nugent and Julia Boniface, a good companion tree is Acacia pendula.

Despite its lack of nitrogen-fixing ability, and despite its broad, shallow roots, it is often used in alley cropping. It is a robust coppicer, and will produce a great amount of biomass, yielding up to 500 kg of fresh leaves a year. This production helps it work as a soil conditioner when used as a green manure. Their presence also helps with water infiltration, reducing run-off when planted densely.

S. siamea is is often grown in the service of Santalum species (sandal wood) — usually S. album – which are parasitic trees, tapping into the roots of other plants for water and nutrients. In China, it is used as a host for the lac bug, which is used to produce shellac.

It makes a good fodder for ruminants, but the toxicity of the alkaloids in the plant make it an ill-advised feed for poultry, pigs, and other non-ruminants. Ruminants only, please.

The young leaves and flower buds are boiled two or three times to remove the bitterness and toxicity of the above mentioned alkaloids, and added to curries. It has traditional medical uses that are now discouraged due to the toxicity of the active compound barakol. Still, there is research suggesting anti-cancer properties in S. siamea.

The wood is resistant to termites, and is hard and durable. It also makes an excellent firewood, and charcoal.

Filed Under: Article Tagged With: trees

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