Rock mulch radiation conduction effects

So after the course with Sepp, I've been thinking more and more about using on-site resources...so I have concrete scraps from posts we removed and I decided to use them as rock mulch for thermal mass and condensation effects.

are there any concerns I should have regarding repurposed concrete?

While placing the concrete, and also adding rocks to some of my hugel beds, I started to think of rocks like radiator fins in the earth and wanted to know if anyone has experience, data, or seen research regarding the effects of rock orientation and the effects on plants, water, temperature, etc.

I might need to draw a picture, basically the thought is for a long skinny rock to insert most of its length into the soil and leave just a bit sticking out to transfer heat from the sun to soil, soil to air, etc. or to half bury a large rock, or to half bury a long skinny rock, etc.

A metaphor might be a ground source heat pump...with the rocks being miniaturized versions. groundsource heat pump

I'm interested in hearing what people think about the various effects of these action and applications of different rock-soil arrangements.

experience, data, and research would be great too...

here's some flicks of what I did...

I do not have any bright ideas for you, but I do have a a question - what are those white tubes for, and what are they made of?

Thanks.

Abundance for All!

Pamela Melcher

I would say your only concern over the concrete ..for use as rocks..would be any plants that really hate alkaline soil like blueberries. You might not realize that they can leach out into the soil.

I have also been pondering the rock for dew and heat holding capacity in my cold michigan area. I have from time to time sat a large rock beside a tree I was growing...I also do this with some logs occasionally just to see if i can see any benefits..

Unfortunately rocks are at a premium here as we have heavy clay soil with very few rocks, we have to bring them in. I put a lot of rocks on my pond island around my waterfall form, so that used a lot of the big rocks we had gathered, so it means gathering more..but we also have some concrete pavers around here and i have a paver sidewalk that is quite broken up that i hope to replace with a concrete sidewalk in the future, (easier to snow shovel and the pavers get overgrown)..so I may have those eventually to add to the food forest to hold in moisture and heat.

Pamela Melcher wrote:I do not have any bright ideas for you, but I do have a a question - what are those white tubes for, and what are they made of?

little white tubes are tree and shrub guards made out of cardboard with bamboo stakes. I have not created the time and budget to fence the area and cottontail rabbits love to eat saplings. they also seem to protect the young trees against sunburn in the winter and drying out in the hot summer winds and sun. for me they are an establishment strategy that I hope to phase out as I get paddocks built. they are most important for conifers and fruit trees which the rabbits love to eat when food is scarce and i did tests leaving some off and lost several trees this way, left on, 0 lost to rabbits, some nibbled at the top on short boxes but still growing.

I'd also like to try the bone sauce method this year to see how it works for rabbits.

Neil, thanks.

How tall are the tubes? What kind of paper do you use? How tightly do you need to secure them into the soil?

I need to protect some trees from rabbits.

Thanks.

Abundance for All!

Pamela Melcher

Sepp Holzer says that his bone sauce repels rabbits.

The vid posted at the top of the forum tells more about it, in case you have not viewed it yet.

Good luck with your trees.

Abundance for All.

Pamela Melcher

Pamela Melcher wrote:Neil, thanks.

How tall are the tubes? What kind of paper do you use? How tightly do you need to secure them into the soil?

I need to protect some trees from rabbits.

basically they are milk cartons, which i used as well, but were too short to protect from rabbits (for my site, demonstrated very well this last winter)

there are many sizes. I select the widest ones to allow some light down the tube. select ones that match the size of your plants. I like the the 3.75" x 14" and 3.75" x 20" from Stewe and Sons stewe and sons

I buy bamboo stakes from Forestry Suppliers bamboo stakes the 1/2" work well, you can ziptie them on if you want, but I put the fat end of the bamboo stake facing the sky and this seems to keep the tree guard on well.

I would like a better method so I'm interested in critical thought around this topic...however this is working for me for now. (trees and shrubs nested within sagebrush, rabbitbrush and desert peach do better but still get eaten in higher %ages than I want). relatively cheap too. less than $0.50 per tree.

Thanks, Neil.

Pamela

On the topic of your rocks-in-bed idea, your suggestion of having a long skinny rock half sticking out from the bed reminded me of something I've started doing as an experiment. I've started filling dark gass wine bottles with water and then burying them in my garden bed with the end sticking out. It's winter here so I figured it would help, although I haven't planted in that bed yet! Something for spring. I don't drink alcohol either so the wine bottles are infrequent. I also use beer bottles as an informal garden edging; I hammer them into the soil by putting some wood between the glass and the hammer. No accidents so far.

think you need to use an air chamber. can you make the rocks in contact with some buried clay pipe?

those foundation air tubes , and the rocks, would make a great pair.
you would want them warmed from both ends, and the pipe could help do that if closed at night.
imagine the wine bottles laying on the pipe would work as well, but would cool off quicker.

Morgan Morrigan wrote:think you need to use an air chamber. can you make the rocks in contact with some buried clay pipe?

do you think the air chamber would assist in heat transfer between rocks and the soil? I think it would slow down the transfer, but I'm not sure how this helps.

is there usually an air chamber in shallow geothermal wells? I thought it was PEX in direct contact with sand.

thanks,
Neil

There is a bunch of interesting research on the talus garland effect in the interior northwest which might be useful for what you are doing.

Deb Berman wrote:There is a bunch of interesting research on the talus garland effect in the interior northwest which might be useful for what you are doing.

Thanks Deb,

A quick search on Talus Garland provided this link to PRI USA
http://www.permacultureusa.org/2009/11/01/rethinking-water-a-permaculture-tour-of-the-inland-northwest/

This article by Kyle is great with some illustrations, a list of the functions and effects of rock piles/mulch, and an example of one build. We can also do this with berms, hugelbeds and swales for a slightly different effect.

I'm definitely becoming more interested in Rock mulch applications and strategies.

I found a drawing on p. 118 of the designers manual that illustrates the radiator effect I'm wondering about. For some reason no Figure number on it.
Imagine the rocks are the metal rod and the soil is the concrete wall and the sun is the flame.

Main differences: rocks conduct heat way more slowly than metal, soil has more air gaps than concrete (I think) therefore better insulated, the incident energy of sunlight is much lower than candle flame (can we put this in temperature?)

any thoughts on the effects of these variations on function and microclimate changes.

not sure about geothermal, but in our outdoor wood furnace hot water heat, the pex is NOT in contact with the soil, the two tubes are surrounded by insulation and then there is an airspace around that and then a corrugated plastic tubing around the entire mess, buried..

Brenda Groth wrote:not sure about geothermal, but in our outdoor wood furnace hot water heat, the pex is NOT in contact with the soil, the two tubes are surrounded by insulation and then there is an airspace around that and then a corrugated plastic tubing around the entire mess, buried..

What is the purpose of this system? to heat water for domestic use in the house? if so, I think contact with the soil would be undesirable because the soil would absorb the heat before the water entered the house.

the shallow geothermal wells I'm familiar with pump heat into an insulated sand 'battery' that stores it, then the heat is accessed during the cold part of the year. in this system, any travel of water from house or heating array to the ground or back would be insulated. my understanding is that within the 'battery' there is direct contact between pipe and sand...similar to the thermal curtain of John Hait's PAHS PAHS info

with the rock mulch radiator fins, the purpose is to store heat in the rocks and transfer it to the soil as warmer or cooler temps depending on the time of year. In my climate we get such massive temperature swings daily (and yearly) that any stabilizing effect helps and a large stabilizing effect helps even more. for example, today we had a low of 30 F and high of 81 F. a week ago it was 101 F.

at this point, row cover and small hoophouses are the tech of choice by local farmers. I'm trying to explore some other options a la Sepp and Paul's suggestions of water and rocks to develop microclimates. I think rock radiator fins are one of many options and would like to improve my understand the overall effect of various orientations and assemblies.

Could you create a shallow pond with dark rocks at the bottom and pump water from the pond to a network of underground pipes to warm up the plant roots? Just like drip irrigation pipes but without any water being released.

You could have two ponds at different levels and the higher one gravity feeds the lower one via the network of pipes and then the lower one pumps the water back up again.

What I've found so far with my experiments with rocks and rockpiles, and my observations of cliffs and talus/scree slopes:

1. Rocks, especially in quantity, have a huge capacity to modify the environment right around them.

2. If you think about a pile of rocks, fairly loosely stacked, (medium sized rocks are what I've mostly experimented with, meaning they are small enough so I can carry or roll them but mostly not so small that I could throw them), it is a mixture or rock and air space. The air travels through the rock pile, and during the day, when the sun is on it and heating up the rocks, warm air is drawn through the pile upwards (thermal chimney effect). At night, when as the air cools down, the rocks are still warm. This seems to cause quite a bit of condensation of moisture in the rockpile, which is largely retained during the warm part of the day (possibly because the ground under the rocks stays cooler than the ambient air.)

3. The type of rock, and its shape, as well as its color, do have some effect on how the rock pile heats up, extracts moisture, etc, but how significant it is in the long run I don't know. My pile of quartz, which is mostly light colored, seems to do a great job of extracting moisture. The rock surfaces are very smooth, so maybe that has something to do with it, or maybe they just feel/look wetter because they are smooth. Basalt, which is very dark, really heats up, so you can get some good thermal chimneys going with it. Concrete is fairly light-colored, so it might absorb less heat and provide less thermal chimney effect. It would be interesting to compare piles of concrete that were dyed different colors. I think the ratio of airspace to rock in the pile is probably one of the most important factors in determining how it will behave. Possibly rock density is also important. I remember once seeing a table on thermal storage capacity of different materials that related it to the specific density of the material in question.

4. I think you might be able to get some good heat transfer to a hugelbed by making an artificial talus slope/rockpile at the base of it, with rocks (or concrete) sacked to create a thermal chimney, and some of the rocks in the pile partially buried in the hugelbed itself to facilitate heat transfer to the soil.

After the Sepp event was over I drove over to the Helena area to visit a friend, who has a tall south-facing cliff in back of her house with a huge talus slope at the base of it. I noticed that there is a belt of shrubs at the top of the scree pile, where turns into a smooth rock face (it was hard to tell how high up it was, but I'd guess 75-100 feet). It seemed like an unlikely place for shrubs to grow (mostly golden current), but I'm guessing that the rock slope/cliff combination produces an ideal modification of climate (temp and moisture) at that spot. I suggested that she hike up there with a bucket of composted manure and some pumpkin seeds and see what happens if you plant pumpkins there (she is just about on the continental divide, at 5600 feet I think, and isn't able to grow winter squash and pumpkins by other methods.)




Cheers
Deborah