Copied and pasted from Daves Garden. Written by nick "Tapla". Dated July9th. 2005.
The purpose is to increase knowledge and not plagiarism.
Regards and enjoy. _________________________________________________________________ The following is very long & will be too boring for some to wade through. Two years ago, some of my posts on another forum site got people curious & they started to e-mail me about soil problems. The "Water Movement" article is an answer I gave in an e-mail. I saved it and adapted it for my bonsai club newsletter & it was subsequently picked up & used by a number of other clubs. I now give talks on container soils and the physics of water movement in containers to area clubs.
I think, as container gardeners, our first priority is to insure our soils are adequetely aerated for the life of the planting, or at least, in the case of perennial material (trees, shrubs, garden perennials), from repot to repot. Soil aeration/drainage is the most important consideration in any container planting. Soil is the foundation all container plantings are built on, and aeration is the most important block in the foundation. Since aeration and drainage are inversely linked to soil particle size, it makes good sense to try to find soil components with particles larger than peat and that will retain their structure for extended periods. Pine bark fits the bill nicely.
The following hits pretty hard against the futility of using a drainage layer in an attempt to improve drainage. It just doesn't work. All it does is reduce the amount soil available for root colonization. A wick will remove the saturated layer of soil. It works in reverse of the self-watering pots widely being discussed on this forum now. I have no hands-on experience with these growing containers, but understand the principle well. There are potential problems with wick watering that can be alleviated with certain steps. Watch for yellowing leaves with these pots. If they begin to occur, you need to flush the soil well. It is the first sign of chloride damage.
Since there are many questions about soils appropriate for containers, I'll post by basic mix in case any would like to try it. It will follow the Water Movement info.
Water Movement in Soils
Consider this if you will:
Soil need fill only a few needs in plant culture. Anchorage - A place for roots to extend, securing the plant and preventing it from toppling. Nutrient Sink - It must retain sufficient nutrients to sustain plant systems. Gas Exchange - It must be sufficiently porous to allow air to the root system. And finally, Water - It must retain water enough in liquid and/or vapor form to sustain plants between waterings. Most plants could be grown without soil as long as we can provide air, nutrients, and water, (witness hydroponics). Here, I will concentrate primarily on the movement of water in soil(s).
There are two forces that cause water movement through soil - one is gravity, the other capillary action. Gravity needs little explanation, but for this writing I would like to note: Gravitational flow potential (GFP) is greater for water at the top of the pot than it is for water at the bottom of the pot. I'll return to that later. Capillarity is a function of the natural forces of adhesion and cohesion. Adhesion is water's tendency to stick to solid objects like soil particles and the sides of the pot. Cohesion is the tendency for water to stick to itself. Cohesion is why we often find water in droplet form - because cohesion is at times stronger than adhesion, water’s bond to itself can be stronger than the bond to the object it might be in contact with; in this condition it forms a drop. Capillary action is in evidence when we dip a paper towel in water. The water will soak into the towel and rise several inches above the surface of the water. It will not drain back into the source. It will stop rising when the GFP equals the capillary attraction of the fibers in the paper.
There is, in every pot, what is called a "perched water table" (PWT). This is water that occupies a layer of soil that is always saturated & will not drain at the bottom of the pot. It can evaporate or be used by the plant, but physical forces will not allow it to drain. It is there because the capillary pull of the soil at some point will equal the GFP; therefore, the water does not drain, it is "perched". If we fill five cylinders of varying heights and diameters with the same soil mix and provide each cylinder with a drainage hole, the PWT will be exactly the same height in each container. This is the area of the pot where roots seldom penetrate & where root problems begin due to a lack of aeration. From this we can draw the conclusion that: Tall growing containers are a superior choice over squat containers when using the same soil mix. The reason: The level of the PWT will be the same in each container, with the taller container providing more usable, air holding soil above the PWT. Physiology dictates that plants must be able to take in air at the roots in order to complete transpiration and photosynthesis.
A given volume of large soil particles have less overall surface area in comparison to the same volume of small particles and therefore less overall adhesive attraction to water. So, in soils with large particles, GFP more readily overcomes capillary attraction. They drain better. We all know this, but the reason, often unclear, is that the PWT is lower in coarse soils than in fine soils. The key to good drainage is size and uniformity of soil particles. Large particles mixed with small particles will not improve drainage because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential. Water and air cannot occupy the same space at the same time. Contrary to what some hold to be true, sand does not improve drainage. Pumice (aka lava rock), or one of the hi-fired clay products like Turface are good additives which help promote drainage and porosity because of their irregular shape.
Now to the main point: When we use a coarse drainage layer under our soil, it does not improve drainage. It does conserve on the volume of soil required to fill a pot and it makes the pot lighter. When we employ this exercise in an attempt to improve drainage, what we are actually doing is moving the level of the PWT higher in the pot. This reduces available soil for roots to colonize, reduces total usable pot space, and limits potential for beneficial gas exchange. Containers with uniform soil particle size from top of container to bottom will yield better drainage and have a lower PWT than containers with drainage layers. The coarser the drainage layer, the more detrimental to drainage it is because water is more (for lack of a better scientific word) reluctant to make the downward transition because the capillary pull of the soil above the drainage layer is stronger than the GFP. The reason for this is there is far more surface area in the soil for water to be attracted to than there is in the drainage layer.
I know this goes against what most have thought to be true, but the principle is scientifically sound, and experiments have shown it as so. Many nurserymen are now employing the pot-in-pot or the pot-in-trench method of growing to capitalize on the science.
If you discover you need to increase drainage, insert a wick into the pot & allow it to extend from the PWT to several inches below the bottom of the pot. This will successfully eliminate the PWT & give your plants much more soil to grow in as well as allow more, much needed air to the roots.
Uniform size particles of fir, hemlock or pine bark are excellent as the primary component of your soils. The lignin contained in bark keeps it rigid and the rigidity provides air-holding pockets in the root zone far longer than peat or compost mixes that rapidly break down to a soup-like consistency. Bark also contains suberin, a lipid sometimes referred to as nature’s preservative. Suberin is what slows the decomposition of bark-based soils. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains.
In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they starve to death because they cannot obtain sufficient air at the root zone for the respiratory or photosynthetic processes.
To confirm the existence of the PWT and the effectiveness of using a wick to remove it, try this experiment: Fill a soft drink cup nearly full of garden soil. Add enough water to fill to the top, being sure all soil is saturated. Punch a drain hole in the bottom of the cup & allow to drain. When the drainage stops, insert a wick several inches up into the drain hole . Take note of how much additional water drains. This is water that occupied the PWT before being drained by the wick. A greatly simplified explanation of what occurs is: The wick "fools" the water into thinking the pot is deeper, so water begins to move downward seeking the "new" bottom of the pot, pulling the rest of the PWT along with it.
Having applied these principles in the culture of my containerized plants, both indoors and out, for many years, the methodology I have adopted has shown to be effective and of great benefit to them. I use many amendments when building my soils, but the basic building process starts with screened bark and perlite. Peat usually plays a very minor role in my container soils because it breaks down rapidly and when it does, it impedes drainage.
I'll give two recipes. I usually make big batches.
3 parts pine bark fines 1 part sphagnum peat (not reed or sedge peat) 1-2 parts perlite garden lime controlled release fertilizer micro-nutrient powder (substitute: small amount of good, composted manure
3 cu ft pine bark fines (1 big bag) 5 gallons peat 5 gallons perlite 1 cup lime (you can add more to small portion if needed) 2 cups CRF 1/2 cup micro-nutrient powder or 1 gal composted manure
3 gallons pine bark 1/2 gallon peat 1/2 gallon perlite handful lime (careful) 1/4 cup CRF 1 tsp micro-nutrient powder or a dash of manure ;o)
I have seen advice that some highly organic soils are productive for up to 5 years. I disagree. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will far outlast any peat based soil) you should only expect a maximum of three years life before a repot is in order. Usually perennials, including trees (they're perennials too, you know ;o)) should be repotted more frequently to insure vigor closer to genetic potential. If a soil is desired that will retain structure for long periods, we need to look to inorganic components. Some examples are crushed granite, pea stone, coarse sand (no smaller than BB size in containers, please), Haydite, lava rock, Turface or Schultz soil conditioner.
I hope this starts a good exchange of ideas & opinions so we all can learn.
A product called magic cloth or magic mop works very well. It is a super-absorbent man-made chamois (100% rayon). Cut in strips, it absorbs & moves water quickly. I've also had good luck with the woven plastic ties that are used to keep citrus bags (oranges, grapefruit) closed until we buy them. Both are effective.
Wicking away the PWT is helpful in many cases, but not a cure-all for soil that drains poorly. It is especially helpful when plantings are young & roots have not colonized the lower portions of the container. Later, when the plants have developed to the point that they need more frequent watering, simply remove the wick & more water is available to the plant after each watering.
Yes, if you're familiar enough with its use & recommended concentration(s). Though it is also helpful in a healthy root environment, it is most valuable when there are root issues like poor aeration or one of the rot fungi beginning to increase in #'s.
H2O2 has an extra O atom (compared to H2O) in an unstable arrangement. It's the extra atom that makes it useful in horticultural applications. Generally, we're not concerned with aerobic forms of bacteria normally occurring in container media or on roots, but various fungi & poorly aerated soils are often a problem.
Since H2O2 is an unstable molecule, it breaks down easily. When it does, a single O- atom and a molecule of water is released. This O- atom is extremely reactive and will quickly attach itself to either another O- atom forming stable O2, or attack the nearest organic molecule.
Many disease causing organisms and spores are killed by O, the free O- H2O2 releases is extremely effective at this. H2O2 can help eliminate existing infections and help prevent future ones. The free O atom can destroy dead organic material (i.e, leaves roots) that are rotting and spreading diseases.
Reduced O levels and high temperatures encourage both anaerobic bacteria and fungi. When plants growing in soil are treated with H2O2 it will break down and release O into the area around the roots. This helps stop the O from being depleted in the water filled macro-pores until air can get back into them. High O levels at the roots will encourage rapid healthy root growth and discourage unwanted bacteria/fungi.
I know it comes in several different strengths. I'm thinking 3%, 5%, 8% and 35% solutions. Cheapest is 35% which you dilute (to 3%) by mixing 1:11 with water. Plastic or glass is best to store it in, & the container should be opaque to prevent light degradation. If three-liter pop bottles are available in your area they are ideal for mixing and storing H2O2. Once you have it mixed at 3% (or start with 3%) mix it at the rate of 1-1/2 tsp/gallon of water as a cutting dip & up to 2-1/2 tsp/gallon to water containers with on a regular basis. Start at the lower concentration and increase concentrations gradually over a few weeks.
H2O2 in high concentration is a powerful oxidant & will bleach skin white & oxidize almost anything it contacts - quickly. This includes living plant tissues, so be careful with it if you use it. A solution that's too strong can kill any organic molecule it contacts.
Excess water: If soil is retaining too much water, it's a sure bet that macro-pores are virtually non-existent (compaction). Removing the water in the PWT will not resolve the compaction issue to any great degree. It really depends on how good (or bad) your soil is.
Please don't think I'm suggesting you repot anything, or even change what you're comfortable with. I only offered the information so those that don't have much knowledge of soils or water movement could start putting things together & perhaps incorporate some of the things they learn, not just from me, but from discussions following the post as well. ;o)
Herbs: Yes, I think you nailed it. In building my soils, I try to consider things like container size, how many plants, sun/shade, etc. and make the soil so it will need watering once per day in the hottest part of summer. As long as you provide nutrients & don't allow the plant to dry completely, a soil that requires watering daily will outperform soils that can go two days, three days, or even longer between waterings. Technically, evaporation isn't preventing saturation, it still occurs, but roots that are in saturated soil, but dry inside of a day (on a regular basis) will show little in the way of ill effects from the temporary lack of aeration. Extend the time to a day & 1/2 in the hottest part of summer, & one of the root rots are likely to take hold. Funny part of that is, the plants will wilt & you'll be tempted to over-water, which only compounds the problem.
Water: Tough question w/o knowing particulars. Do you have municipal water? know the pH of it? Alkalinity level (it's different from pH in case you wondered)? Find out? What kind of soil are you growing in? My first inclination is to say yes, it's worth it, especially if you're as particular about your containers as I. If you find the pH of your water is higher than 8.5 at any time, it would be worth it. Our water here is surface water from Lake Huron, which is usually lower in pH than ground water. After obtaining an analysis from our municipal supplier, I discovered that our water ranges from a pH of around 8.1 all the way to 10. I remember how I struggled 10 years ago before I acquired a reasonable working knowledge of soil chemistry. I think I would have problems with the pH of my water if I hadn't paid attention to business & learned ways to work around nutrient problems. If I had the opportunity - I'd try it for a couple of months on at least a portion of my containers. It could make a huge difference, or non - no way to tell w/o looking into it more or experimenting. ;o)
Terry - I have never read anything scientific on this question. I have asked scientists about the use of H2O2 as an anti-fungal, and a temporary soil oxygenator for O2 stressed roots. Their replies were something along the lines of what you alluded to above, but not that it was a soil-surface sterilizer only. My observations (though purely anecdotal) do not support that either. H2O2 is probably considered a topical because it reacts with (oxidizes) the first organic molecule it contacts. Common sense tells us that a portion of the chemical, mixed with water, will perc through the soil before contacting other molecules.
I have used H2O2 to water my indoor plants during the over-winter period for nearly two years now. I use 1 oz of 6% solution I have diluted from 35% food grade per L. of tap water. I have observed no problems with rot fungi during that period, even in plants where soil conditions would cause me to expect a problem to come calling (some plants are over-wintered, badly in need of repots due to lack of time on my part) collapsed & soggy soil being one. I also have noticed better growth and vitality, increased resistance to insects, and better color. Given some of the shallow containers my plants are in (shallow containers have a very high % of saturated soil and are more difficult to keep rot and soil-insect free) I should expect some rot issues and soil-insect presence, but have noted none, unlike in past years.
I cannot attest to whether H2O2 might be effective in eliminating an infection of either pythium or phytopthera, but it appears to have effectiveness at preventing fungal spread. Again, this may well be scientifically refuted, and what I observe may have basis in another cause/effect relationship. I'm usually quite careful about what I attribute things I observe to, but I am comfortable in my belief that including H2O2 in my watering program is compatible with and an aid to my growing methodology.
Best I can do - wish I could help more, Terry.
Regular lime is calcium carbonate, CaCO3. There are other versions, including dolomitic lime (calcium magnesium carbonate) or hydrated lime (calcium hydroxide). All will raise the pH. This is necessary in some cases because the peat and pine bark in the mixes above is fairly acidic, with pH readings as low as the 4 range. Most peat-based commercial mixes have some sort of lime to neutralize the acidity of the peat.
I use dolomitic lime. My reading leads me to conclude that it is superior for two reasons. First, it contains the magnesium which is sometime deficient in container mixes. Second, it acts more slowly and gradually than, for example, hydrated lime. I adjust the amount of dolomitic lime depending upon the pH requirements of the plant and upon the other ingredients of the mix. If I'm using coconut husk chips instead of pine bark fines, I use less dolomite, because the CHC is closer to neutral pH than the pine bark. If I needed a really acidic mix, like for a Miracle Fruit tree, then I could use pine bark fines and peat and leave out the lime entirely. (I don't have a Miracle Fruit tree yet, but that's my plan!)
I will post more info as i come across it but you all can argue in peace. _______________________________________________________________
Hi Lynn ;o) You may be surprised to learn that sphagnum peat holds about 90% water by volume at saturation and gives it up over a fairly even curve until it becomes so tightly held in the media it is essentially unavailable to plants at about 30 kPa when it still retains about 30% water. #2 and #3 vermiculite both hold about 71-72% water at saturation and give it up over similar curves until they reach about 30 kPa with about 28% remaining as unavailable to plants.
What this means is that when peat and vermiculite reach about 30% water content, they both hold water so tightly that plants cannot extract it from the media. However, peat initially holds about 28-30% more water by volume than vermiculite, so it is actually a better choice than vermiculite insofar as water retention is concerned, especially since their availability curves are similar.
You may wish to consider adding some polymer or starch granules specifically packaged to sell as a moisture retention aid, or include some rock wool in your soils. Rock wool holds about 90% water by volume at saturation and gives it up over a steep curve, making almost all water held available at tensions as low as 5 kPa. It also does not become hydrophobic when it dries down like peat. I think I would retain the peat in the mix and replace a portion of the perlite with rock wool.
Hi, Rj By "lava sand", are you referring to zeolite or specifically the product ZeoPro? It's purported to have some kind of extraordinary CEC, but from recent conversations with some whose judgment I trust: "... I didn't see results that made feel I can't do without this." There's nothing stopping you from trying it out & letting us know your findings though.
You may also wish to consider substituting a calcined clay product for any perlite in your soils. Calcined clay aggregates (such as Turface MVP) have an excellent CEC capacity (if it means anything, up to 12 me/100 cc) and 40-50% internal porosity. This translates to good water holding capability (over perlite since it has 0 usable internal porosity) and a whole lotta cation attachment sites @ more than 13 acres of surface area per lb of aggregate.
Build your soils and select container sizes so that you can go at least 24 hours between watering in the heat of summer and when the planting is mature. If you do this, you could well be over-potted early in the grow season when the planting is immature & roots have not colonized the container completely. If such is the case, then is the time to use a wick - until you need to water more frequently than you are willing to. At that point, remove the wick to increase irrigation intervals.
Finer sands will increase water retention and can provide enhanced drainage in some soils, but they generally do so at the expense of aeration. What I consider appropriate-sized sand for hort applications is going to be about 1/2 BB size or larger. I've used screened products: coarse silica, crushed granite, pumice, and Turface all extensively with very good results, but only find them necessary in soils that need to be formulated for extended life.
As far as the sand you refer to "facilitating a greater nutrient absorption rate by the roots, I would have to say that is probably technically not accurate. It may be true that it could prove beneficial by holding onto nutrients that can readily go into solution and then be absorbed by the plant, but it won't likely increase absorption over and above what any adequate nutrient supplementation program would. Plants absorb water and dissolved nutrients when the moisture (matrix) tension of soils is lower than the cellular tension and is probably unaffected by what soils are comprised of (structurally speaking - pH assumed appropriate) so long as air/water/nutrients are present in appropriate ratios.
Oh - it probably doesn't matter much if you apply that much water, but it does tend to increase compaction, which is a valid reason to water via wicks to begin with. The description I gave is well-supported in bonsai culture, where watering plants is made into a very exacting science, so I'm pretty comfortable offering it up as a guideline. Copious top-watering also tends to leach nutrients along with accumulated metal salts, increasing the necessity for additional fertilizer applications. I know Bob already knows all of this, so I offer it mainly for the other readers. By reading his posts, I'm sure he's pretty well satisfied with his methods and has this well-covered.
While I'm here though, I might offer a tip on how to water a container thoroughly and efficiently:
Wet the soil thoroughly over the entire surface (I almost always try to keep foliage dry), using what you gauge to be the approximate maximum volume you can apply w/o water draining from the container bottom. Wait 10 minutes while the water also disperses laterally through the container and water again so that about 10 - 15% of the total volume used on that container drains from the bottom. This method effectively allows accumulated salts to go into solution and flushes them from the container in draining water when done on a regular basis. Of course, this is assuming your soil is well-aerated and drains well enough to allow this kind of watering.
I've got all-day sun on my deck, so I do use polymer moisture crystals in all my pots... when it's less hot, I can skip a day of watering, and even when it's 100 degrees I only have to water once a day (without the crystals, I'd be watering twice a day and plants would still droop).
I know a great place to get bulk quantities (2 lbs, 10 lbs, or even 55 pounds which I just ordered to split with a friend) of moisture crystals: http://www.watersorb.com/index.htm. Even with shipping (included in the price), it's cheaper than buying the containers of "Soil Moist" et al. at the box store or the nursery. "Medium" crystals are the right size for containers. Don't put in more than the recommended amount -- when the crystals expand, your potting mix will heave around, or the crystals will come popping up and over the lip of the container like weird little jello cubes -- a little goes a long way. ________________________________________________________________________
H2O2 has 2 O atoms, unlike water which contains only one. Chemically, it's an unstable chemical compound. Ions with the right potential range for reduction in nutrient solutions act as catalysts for the reduction of H2O2 to H2O. This reaction releases O atoms, providing extra oxygen to the plant roots and improving root function. It also and oxidizes metallic elements, making them more readily available for plant uptake.
As you note, the water doesn't "sour" because the H2O2 reacts with and kills organic molecules that contain catalase.
I wasn't sure about your question - I hope that answered it.
Well Marilyn, I have a half dozen hardy hibs in the ground & use at least a half dozen tropicals each year in containers, so I have some experience in growing them and coaxing lots of blooms out of them. The soil mix above is very good for hibs, but there is a better mix if you want to talk about it. Let me know.
Hibiscus appreciate a light and coarse soil, similar to that above, mainly for the drainage & aeration they provide, not particle size. Soils that are mainly fine peat tend to compact and hold too much water, resulting in badly aerated roots and rot issues, so remember aeration is particularly important with hibs.
Assuming you'll use a fast draining soil: for best flowering, plan on fertilizing EVERY week with a full recommended dosage while the plant is actively growing. They're pigs & love fertilizer. You'll have to translate these numbers into whatever you can find in organic fertilizers, but I can tell you you'll be hard pressed to keep up with their nutrient needs with organic nutrient supplements. Water soluble formulas can be used with every watering at lower doses if you want, but I find that a pain & weekly is just fine. Most use a "bloom-inducing" blend like 10-52-10 or 15-30-15 on hibs, thinking the extra P will induce blooms, but they don't especially like P. Look for something with a low P (middle number) content. If you could find a soluble 20-5-20, it would be great. Blends high in P like listed above, or even 20-20-20 will produce lots of fine leaves & far fewer blooms. For best vitality, plan on adding some Epsom salts & chelated iron or your organic source of Mg and Fe into your fertilizer program, too.
Potting up is best about now where you live. I treat them like trees & bare-root/root prune every year, but you can score the root mass several times vertically with a razor knife. Pull a few handfuls of roots off the bottom & sides (don't worry - this will not kill or harm this vigorous plant) and pot in the next larger pot. If you're using a very fast soil, you can use a very large pot if you prefer. The plant will grow buck-wild. ;o)
I hope that helps, Marilyn. ___________________________________________________
Pirl - I usually use the mix described in the original post for veggies, pretty flowers (garden display container plantings) ;o), or anything else I consider short term plantings. Don't misunderstand - the bark-based soil mix will outlast a peaty mix by far, but I still usually turn the soil into the garden or compost each year & make fresh, - that's just how I am. ;o)
I use a variation of the mix I just described to Marilyn immediately above for all things woody at the first repot. For roses, I would use the mix I described to Marilyn, but add a little more bark & some peat to it; clematis would get the same soil as the roses and I would double pot them, trying to be sure the outer pot was white or light in color (cooler roots); dahlias would go in the original mix (first post).
It doesn't HAVE to be this complicated at all. Almost everything will grow better in the original mix than in a bagged soil. I didn't mention this other mix because the average grower won't want to be bothered with building it, but you guys are asking questions, and I'm just trying to provide the answers w/o regard to what may (or may not) be involved in finding suitable ingredients. I find them extremely easy to come by, but others may not.
I can say this though: If you take the time to find a source for and learn the function of the individual ingredients in a soil, and how to combine them to suit an individual planting, you'll be very impressed with the results - particularly how much easier everything is to care for. The down side is that you'll need to water and fertilize more frequently in any soil I suggest when compared to a bagged soil, but from a physiological perspective, that's a very good thing.
Rose - the echeveria in the 2nd photo up, is growing in 3 parts Turface, 1 part coarse silica sand, 1 part crushed granite, and 1 part pine bark. That's a mix with only 17% organic component, and she's at least 15 years old & marvelously vital. I have other plants growing in 100% Turface - that's NO organic component, and they do spectacularly with only a little attention to making sure I supply the appropriate nutrients in my fertilizer program.
use Miracle Gro 12-4-8 liquid fertilizer at 1 capful per quart once per week (in a fast soil that drains freely). Cut the dose by half if you use a bagged potting soil. I also supplement with a little Epsom salts every so often (probably every other week, I'd guess) when I think of it.
Turface is a calcined (high fired) clay that is ceramic-like. It's very air and water porous & holds water & nutrients very well (excellent CEC). One pound of Turface has 13-1/2 acres of surface area. It's an excellent soil amendment, used extensively on athletic fields & golf courses because of the properties listed. Additionally, it adds porosity to soils, promotes drainage, and is extremely stable. See Turface at lower left & crushed granite at lower right.
Brick factory waste. That is what I am working on. So far my experiments have produced very good results. Problums Availability, too small and too big coponents, sieving and separation of various size particals.