Let's talk soil amendments, e.g. pumice, pine fines

bluegirl_gwNovember 26, 2013

After reading various discussions on the soil & cactus forums, I got very interested in pumice as an amendment to heavy clay soil.

Never could locate it in my area, even as DryStall horse bedding. Where pumice is locally available--CA & AZ it's widely used.

So, after studying the forums, I started experimenting with calcined products--calcined clay kitty litter, Napa #8822 Floor Dry (calcined diatomite), Lava Sand--fine textured red lava rock.

As I understand it, the calcined products are fired so that the clay doesn't break down to silt.

In my casual experience, all of these work well to improve the tilth & drainage of the heavy clay I tried them in. I was dealing with dense black "gumbo" clay of the TX gulf coast.

Another place they have been beneficial is in cutting rooting media. I noticed that Vintage Gardens & several other places send their roses rooted in a media heavy on the red lava pieces (up to maybe 1/4" size), & perlite. I don't know if the other component is peat or coir--it is dark & fine. I've been using coir & it keeps the media moist but not so saturated as to cause rot.

So it's also nice to learn (Strawberryhill, Garden tips thread) that the calcined products & lava sand also have nutritive value to plants besides improving soil tilth & drainage. It seems that even the silica in them improves stem strength in plants & there are some interesting anecdotal & experimental data to support this that Straw has posted on the garden tips thread. Lava sand is available in my area, not too expensive, Napa #8822 is $6.50 per 20b bag, various calcined clay kitty litters for about that price.

Another well-liked amendment that it took a while to locate in affordable amounts was pine fines--used in all sorts of mixes from Al's Gritty Mix to citrus potting (5:1:1 mix) etc. I never could locate it in affordable quantities & was sifting shredded bark for awhile.

But Lowe's carries a mix called HapiGro landscape mix & it looks to be 90% pine fines, very nice texture, flakes about 1/4". Quite affordable, a huge bag runs~$5.00

I'm finding coir bricks locally for about $6-$6.50 per brick.

Now I'm dealing with caliche--a dense calcium carbonate common in desert soils. But it appears that coir, pine fines & lava/calcined clay products may be useful for soil mixes in this zone, also, both to improve texture & to counter the alkaline water & desert soil. Ironically, gypsum, too. The calcium of caliche isn't chemically available to plants to adsorb & the alkaline soil & water benefit also from the sulfur available from calcium sulfate. Gypsum is pretty reasonable, around $8.00/40lbs.

So what amendments are you finding useful & where the heck have you found them?

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strawchicago(zone 5a)

Hi Bluegirl: Thank you for very good info. I appreciate what you post, that will help folks with rock-hard clay. I looked up caliche, that's the stuff I have, hard enough to break up a shovel. My husband dig holes with pickaxe ($40 high-quality).

My best performers Firefighter rose, Sweet Promise, and Liv Tyler are fixed with 30% pine bark, Next best performer is planted in good potting soil, topped with native clay.

My worst performers are fixed with peat moss, which glued up to my clay. Next worst performers: bagged soil (sticky clay stuff), sand (also glue up, unless it's the entire bag at the bottom, and NOT mixed in).

The guy who reported NAPA Floor-dry being too wet ... bad for his pots are from my area. He's in Wisconsin. Spring flash flood is common here. Susan in Illinois, zone 5, reported Turface made her roses water-logged & lost leaves. We have heavy rain in spring/fall.

Turface is sold as Schultz soil conditioner at Ace hardware under a different name, but it's still "calcined clay", with pH of 6.2. Composition of Turface:
SiO2 (Silicon Dioxide): 74%
A12O3 (Bauxite): 11%
Fe2O3 (Iron (III) Oxide): 5%

NAPA floor-dry is neutral to alkaline. Thank you, Bluegirl, for the info. on #8822 Napa Floor Dry for $6.45 for 25 lb. bag. Here's a quote from container forum: "NAPA auto sells two types of oil absorbent. One is called oil dri in 40 pound bags. ....it is soft clay pellets. The good stuff is called Superabsorbent in 25 lb,bags, it's the diatomaceous material that you want."

Pumice is neutral in pH. Coco-coir pH is 6 to 6.8, and pine fines pH is 4.5. From horticulture studies: Both coco-coir and pine fines lead the pack in flower-production for roses.

Someone asked me if perlite and vermiculite can break up hard clay. Small and soft particles glue up to clay immediately, more water-logging. I already tried perlite with clay ... it killed 2 baby tomatoes in heavy rain. U. of Colorado specified that vermiculite should NOT be used to fix clay, due to its water-retention & break down easily.

I locate the chemical composition of red lava rocks: high in iron. Its class is described by Wikipedia as "Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium and iron." More info. on red lava rock: "... basalt and scoria (a red-coloured rock that contains large amounts of iron-rich minerals)"

Info. on pumice: " Rhyolite is light-coloured or white ��" this is a clue that the rock contains a lot of silica (more than 70%) and not much iron or magnesium. Some rhyolitic rocks are quite light, for example, pumice, which may still have evidence of the bubbles of gas trapped as the rock solidified."

Silica, as in NAPA floor-dry (diatomaceous earth), or Pumice, do strengthen cell walls against diseases. Cannabis growers testified that NAPA floor-dry is superior to perlite, in producing thicker stems and healthier plants.

Bluegirl, thank you for the info. on red lava bits in Vintage's band. When I get roses from Roses Unlimited .. it's mostly pine fines, peat moss,, and black & shiny granite bits.

Here is a link that might be useful: Types of vocalno rocks

This post was edited by Strawberryhill on Tue, Nov 26, 13 at 11:23

    Bookmark   November 26, 2013 at 10:22AM
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strawchicago(zone 5a)

Two sites I found stated that Lava sand is high in iron .. that would fix chlorosis in plants. The last site explained it well, so I'll post it here. Too bad we don't have lava sand nor green sand like Texas ... we only have lava rocks. My neighbor with 40+ roses use black lava rocks to mulch her roses: zero diseases, very healthy.

"Lava sand is derived from pulverized rock. The fertilizer is insoluble; hence adding it to the soil wont affect the pH value. Lava sand resists compression and adds structure to soil, while retaining far less water than compost or clay. During testing, lava sand retains roughly 40% of its own weight in water, compared to 160% for fine-screened compost and 250% for smectite clay. The fertilizer has lower water retention hence it can help your soil dry out quickly. Coarse, quick draining soil is also easier for roots to tunnel through, so adding this lava amendment to your soil can enhance the deep root growth."

• Lava Sand benefits both clay and sandy soils. • It acts much the same as expanded shale and has the benefit of being completely natural and organic. • Lava Sand is made up of crushed volcanic slag or dried lava even though it has a sand like texture it is full of holes that allow for moisture penetration and water holding capabilities.

• By its physical structure and chemical makeup lava sand helps the soils natural nutrients become more available to plants and helps keep heavier clay particles in the soil separated making the soil more active. • Lava Sand is paramagnetic, that is, it is affected by a magnetic field but does not itself become magnetic.

Here is a link that might be useful: buzzmobile's post on lava sand

    Bookmark   November 26, 2013 at 11:11AM
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Thanks for looking up & posting all that good info. It is very useful for my soil & climate situation. I don't recall what the lava sand cost--got it last spring, but it's heavy as heck. It's a big bag that has grain size from coarse sand to 1/4" nuggets. I sifted it to a medium grain size mix to add to a cutting media I was preparing.

I'll plan on utilizing the bigger stuff on the roses--sounds like a good iron source, plus micronutrients. Iron is terribly tied up by the alkaline water & caliche. I've spread some ironite, an iron sulfate granule product plus some liquid stuff. All had limited improvement on chlorotic roses & I burned the heck out of a couple of roses--oops. Back to organics & concentrating on healthy soil to get healthy plants.

I guess pumice, calcined clay & lava aren't technically 'organic' in that they're not carbon-based, but thought it would be okay to discuss them here as they aren't artificial 'chemical' amendments.

Another surprise has been how much plants like charcoal. We burn a lot of cedar brush & after I hose down the burn pile I shoveled it around on top of areas I'm colonizing for future beds. I expected the areas to get scalded out by the ash. But maybe since the ash was hosed off at the burn area, it didn't sterilize the area I spread it with excess alkalinity. The texture of the leftovers was like coarse animal feed, pure black chunks & grains. The native grass & wildflowers went nuts where I spread it.

So now I scatter the burned charcoal around the roses after I wash it down.

I'm gradually getting a lot healthier leaves, good basal production & more flowers--just through dumb luck by spreading organic stuff that's available around here.

    Bookmark   November 26, 2013 at 5:31PM
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strawchicago(zone 5a)

Hi Bluegirl: My Mom had the best garden in MI fertilized with wood ash for 30 years. Her 5-acre land used to be a chicken farm, and the veges she grew were super-sweet. I jokingly accused her of putting sugar in her veges.

I read a review on Chickity-doo-doo, and the person said her veges grew on that stuff was sweet & best tasting. It must be the high zinc, boron, and copper & trace elements.

Just a bit of trace elements can make the plants go nuts. My fruit trees were stingy with chemical 10-10-10, then I used chicken manure last year, and the peach tree was so loaded that the branch broke.

Wood ash is high in trace elements, same with RED lava rock. My perennial bed went beserk with blooms when I buried RED lava rocks (I meant to stop yarrow from spreading by that trench) ... but it backfired and plants went bonkers with blooms.

I read Cheryl Netter's rooting by baggie method: She used Peter's potting soil, and 1/2 perlite or vermiculite. Perlite is known for both water-holding ability, and aeration. Vermiculite is expanded silicate (mica).

Scott bought Peter's, and that excellent stuff is no longer available. Since Peat moss is acidic at pH 4, some brands add dolomitic lime to supply calcium and magnesium. But Peter's potting soil added bark ash (alkaline), which supplies calcium, potassium, magnesium, and all trace elements. Metro Mix also has bark ash, and is used in greenhouse veges seedlings.

Peter's Professional Potting Soil Grace- Sierra
Canadian sphagnum peat moss, vermiculite, granite sand, bark ash, nitrogen, phosphorus, potassium, calcium and other minerals, wetting agent 5.8-6.8

The below link detailed the ingredients in popular brands of potting soil.

Here is a link that might be useful: Soil guide - all about potting soil

This post was edited by Strawberryhill on Thu, Nov 28, 13 at 15:16

    Bookmark   November 26, 2013 at 10:23PM
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strawchicago(zone 5a)

There's a 2 years study by Colorado State University on potting mixes by Carl Wilson, Extension Horticulturist. Here's an excerpt from the link below:

"Second, Hyponex All Purpose Potting Soil and Green Charm resulted in poor plant growth. Both of these media contain sedge peat, a fine particle material that tests to a low porosity. There simply isn't enough space within these media for the water and air that plant roots need to grow successfully. Black Gold All Organic Potting Mix resulted in significantly less plant growth in one out of two years.

Here is a link that might be useful: Cosumer Beware Potting Mixes Choices

    Bookmark   November 26, 2013 at 10:28PM
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strawchicago(zone 5a)

I can see why perlite is used in the baggie-method to root roses: it's light-weight, holds water,and create air space for roots to breathe. Here's an excerpt from link below:

"Perlite is a volcanic rock that has been heated and expanded to become a lightweight, white material. Perlite is sterile and pH-neutral. When added to a soil mix, perlite can improve air space and water drainage. It is a hard material that does not break apart easily. Perlite pieces create tiny air tunnels, that allow water and air to flow freely to the roots. Perlite will hold from 3 to 4 times its weight in water, yet will not become soggy. Perlite can be used instead of sand to reduce the soil mix weight. It holds very little water and costs are relatively high. It is much lighter than sand and can be used instead of it.

Vermiculite: Handled gently, vermiculite provides plenty of air spaces in a mix. Handled roughly, vermiculite compacts and loses its ability to hold air. Vermiculite holds water and fertilizer in the potting mix. It also contains calcium and magnesium, and has a near-neutral pH. Vermiculite comes in different grades. Medium grade is usually used for starting seeds. "

Al Tapla in Container Forum explained that perlite holds water on the outside, and vermiculite holds water in the inside. University of Colorado specified that vermiculite should NOT be used to fix clay soil.

Here is a link that might be useful: Organic potting mixes

This post was edited by Strawberryhill on Tue, Nov 26, 13 at 23:35

    Bookmark   November 26, 2013 at 11:31PM
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sandandsun(9a FL)

"Another surprise has been how much plants like charcoal. "

Pot ash

Here is a link that might be useful: Potash

    Bookmark   November 29, 2013 at 10:39PM
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strawchicago(zone 5a)

In the Rose Hugel blog below, Gardenseek posted on his experiments in large pots, with only 4 hours of sunlight in hot San Francisco. His experiments with roses, peppers, and eggplants showed that natural stuff: leaves, logs, branches, compost yield far better harvest than man-made stuff: 50% pine fines and 50% Turface (did very poor).

If you watch both of his YouTubes in the below link, the best result was with Vertical logs placed at the bottom of the pot for drainage and air-flow to the roots. Vertical logs also wicks up moisture best. The second best result is broken branches, mixed with leaves & compost at the bottom ... retain moisture very well.

The next best result is soil mixed with leaves & compost. And the worst result was 50% pine fines mixed with 50% Turface (calcined clay). See link below:

Here is a link that might be useful: Rose Hugel experiments in pots

    Bookmark   December 4, 2013 at 12:49PM
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strawchicago(zone 5a)

Below link is an Horticulture Abstract as to the effect of particle-size of pumice in growing cucumber, roses, and lettuce:


"In contrast, lettuce, and to a greater degree roses, exhibited a weaker response to the different pumice grades and growing systems. The two finer pumice grades were characterized by relatively low air-filled porosity, which presumably restricted plant growth and yield as a result of poor root aeration. The coarsest pumice grades were characterized by a steep drop in the water content."

Another excerpt from the below link on how coco-soil (from coconuts) beat pumice in rose-flowering. The research is entitled "Rose-cultivation with coco-soil versus pumice".

"As far as flower production was concerned, more flowers were harvested from plants grown on coco-soil than on pumice, independently of the planting density. On the other hand, stem length and weight were the same in rose flowers produced on both substrates. " See link below:

Here is a link that might be useful: Comparative study of coco-coil vs. pumice soil

    Bookmark   December 7, 2013 at 6:29PM
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Desertgarden- Las Vegas, Z8b @ 2800 ft.


I have alkaline clay soil high in calcium carbonate, for the most part, and add gypsum due to the salt build up. Gypsum was suggested after professional testing, and this Fall was the first time I added it in the soil amending process; hopefully I will see healthier plants. BTW, I purchased it from a local nursery and found it to be relatively inexpensive.


    Bookmark   December 7, 2013 at 9:37PM
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strawchicago(zone 5a)

Hi Lynn: Thank you for sharing your experience with gypsum. EarthCo. also recommended gypsum for my soil ... never mind that I'm next to a limestone quarry, plus a gypsum plant. Bluegirl wrote in another thread on how she broke up her clay with gypsum. I have similar success using gypsum to break up my rock hard-clay.

I get gypsum for $7 for 40 lbs. bag at my local feed store. It's quite acidic (has a higher % of sulfur), and burns my hand. So I always wear gloves when handle gypsum. The Encap sulfur sold at Menards $6 for a tiny 1 lb. bag contains a good % of gypsum .. I no longer buy that sulfur bag, since gypsum is cheaper, plus U. of CA at Davis documented that 1 lb. of gypsum is equivalent to using 5 lbs. of sulfur.

I agree with their research. I put tons of that Encap sulfur on my clay ... did nothing, until months later, and tons of rain (at pH 5.6) ... then the soil finally crumble. With gypsum, it takes a few days to make my clay fluffy.

Many sites and U. of Extensions alert that superphosphate harms the mycorrhizal fungi that help roots to obtain phosphorus & other nutrients from soil. However, Roses Unlimited recommended putting triple super-phosphate NPK 0-52-0 in the planting hole. So I put that stuff inside the planting hole of Queen of Sweden, plus sulfur. The flowering is 1/2 the rate of other roses without superphosphate. That's for 2 consecutive years.

Last month I dug up Queen of Sweden, the root is woody & fibrous and reached down below. But there's an absence of secondary roots, or cluster-network. I didn't put superphosphate in Honey Bouquet, and when I dug that up, there's the fibrous brown woody main trunk, plus a vast network of secondary roots. Honey Bouquet gives 3 times more bloom than Queen of Sweden, at 1/5 the size.

One of the danger of superphoshate is it also contains the toxic chemical cadmium, that would be poisonous is absorbed in edible plants. Plants can only utilize a small percentage of given phosphorus, the rest is quickly bound up with other elements in alkaline condition. When I use superphosphate in soluble form, as in MG Bloom Booster, it's really hard to dissolve. So I put vinegar in the bucket ... yet I still get phosphorus crystal stuck at the bottom.

See below link of Australian Agricultural field study that showed APP (ammonium polyphosphate in fluid form) surpasses granular phosphorus. There's another Australian study that showed that the use of granular phosphorus over a span of 5 years did not increase their wheat yield much.

I tested SOLUBLE Bloom Booster NPK 10-52-10, similar to APP, and the result was very good, if I use at 1/4 dosage. Too much chemical phosphorus can burn roots. Just a little bit helps roses with wimpy roots that can't acid-phosphatase, such as Jude the Obscure.

Most roses don't need Bloom-Booster, they can secret acids to unlock phosphorus-tie-up in alkaline clay. It's the wimpy own-root like Jude the Obscure that has to be spoon-fed due to my alkaline water at pH 8.

I use soluble fertilizer for pots, since pots leach out nutrients with our rain. In my alkaline dolomitic clay, no need for chemical fertilizer. My clay is fertile, with plenty of bacteria to fix nitrogen (air is composed of 78% nitrogen). I don't fertilizer my 26 trees, yet they are taller than 2-story house, plus lose leaves every winter. See picture below of my center garden, zone 5a Chicagoland:

Here is a link that might be useful: APP fluid fertililzer surpasses granular phosphhorus

This post was edited by Strawberryhill on Sun, Dec 8, 13 at 14:53

    Bookmark   December 7, 2013 at 10:30PM
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