Gritty mix problem. How do I tell if the mix is too wet ?

12 years ago

I am using A1 granite grit size 10 and I found out that its too small. I already made a big batch and now I need to amend it with more granite grit. Is there a method or rule of thumb to tell if the mix is holding too much moisture so I can adjust it accordingly?

I will be getting the a1 size 5 granite grit 1/4". This is the ideal size correct ?

I only water once a week so I used a 5 part turface and 3 part granite grit in the photos below. It has no fine bark.

From the photos you can barely tell there are any granite in there.

Thanks

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Comments (4)

nguyenty
Original Author
12 years ago
I just bought the number 5 granite grit

number 10 on top, 5 in middle, and mvp turface on the bottom. Is number 5 granite too big ?

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b_brae
12 years ago
So, here is what I've learned.

My first bag of granite was A1 Grit's Poultry #10, from the feed shop, and I thought that was just about right. My next bag was from a roofing co., A1 Grit #10, it was a coarse sand, just like in your photo's, but the bag did not say Poultry; the roofing supplier said to get the #5, and this is good too. I now buy #5 crushed granite from a gravel/landscape supplier, it is nice and sharp, I use a 1/8" screen as there is some sand. I guess A1Grit has a unique sizing system?

I understand the turface can be screened to finer size on the lower end, roughly 1/16" as it runs small. The granite (and bark) can be a touch larger about 1/8" to 1/4" overall; too much size difference and the mix could separate.

I'm not sure how you'd remedy your problem with the small granite already mixed.

Doug
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My experience here in hot arid Fresno has been somewhat the opposite. We've had little rain since I've bare rooted six (so far) new citrus, each during spring flush, into 15" containers with gritty mix. I have different trees in different soil (Turface, Napa Absorb, Playball, Axis) but they seem to behave the same. All were dust screened and I even sifted turface into two sizes (large+small) so I could vary a mix if needed even beyond varying the granite. Instead of using an equal Granite part, I removed 20% of granite and replaced it with Turface. A .8:1.2:1 instead of 1:1:1 so it would hold MORE water. My granite is a tad smaller than gran-i-grit in theory drains a bit less. I found it VERY helpful to do basic testing before I put the citrus in the mix. Most importantly, I used the containers I was to grow in, filled them with the mix, and simulated a watering. Then scooped one out after one day, another after two days, etc. to see the moisture levels. Later I varied it while in direct sunlight vs. shade and with significant daily "overwatering" ie. rain. For kicks, I put the mix in a bucket without holes and after about a week it became smelly rotten just like anything else would. MY SOLUTION I'm putting an extra layer of sifted bark fines to use as a mulch. Not too much, just one solid layer so the mix isn't visible anymore. Then I sprinkle a bit more turface on top and a thick ring near the outside edge to help keep slimy kritters out. This significantly improves the moisture consistency between the shallow vs. deep layers of the mix -- although it is still clearly different. Here in Fresno with very low humidity, when temps run in the mid 90's it needs water every day+half. When temps are in the low 80's it makes it two+half days. I can push it by adding one more day to each, knowing the bottom portion of the container is still somewhat moist. I have a similar experience with the above posters because of the *obvious* difference in moisture levels with the gritty mix the deeper you go. The top 2" or so would completely dry out-- so dry that dust would fly off in a breeze and it reverts back to it's original dry coloring. Yet the bottom portion would still be moist. However, where my experience differs is I require water nearly every day. I was initially shocked because without the mulch layer, when the temp hit 100 degrees, my 15" test pot was almost completely dry half-way down after 24 hours. I still keep one "baseline" container full of mix and water it just like I do the citrus, just in case I need to see exactly what the moisture is like or if I want to test adding more/less of a component.
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tapla (mid-Michigan, USDA z5b-6a)
12 years ago
Nguyenty - it looks like your Turface has already been screened? The #5 gravel looks very good - about the same size as the granite or cherrystone I use.

You're better off with the granite fraction being a bit too small than the Turface fraction, because the granite holds so little water comparatively. I think what I would do is use it as is. I wouldn't fertilize at each watering because I suggest you DO water in sips, with an occasional flush until the roots have colonized the soil mass. At that point, with an established planting, it becomes less likely you could over-water.

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..... not lecturing or being snotty. Think of it as a reminder to anyone following along ~ The reasoning behind the gritty mix: it provides a soil with little or no perched water that retains it's structure indefinitely. If anyone is going to build a soil similar to the gritty mix but lacking these two properties, there is little sense in going through all the effort when something like the less expensive and easier to make 5:1:1 mix would serve as well.

Really glad to see you made the effort. I hope you let us know if in the end you think the dividends justify the diligence.

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succulent_succotash
10 years ago
Similar to nguyenty, I do not have access to Gran-I-Grite, but have found A-1 Grit available from several local feed stores.

I have not screened my turface yet, so I don't have a size to compare the granite particles to.

***Should I get the A-1 Grit No.5 (1/4", 0.25") or No.10 (1/8", 0.125)?

Al's Gritty Mix calls for Gran-I-Grit No.2 Grower (3/32"-3/16", 0.09"-0.18").

***Based on the above, what screen size should I filter through?

Gritty mix problem. How do I tell if the mix is too wet ?

Comments (4)

nguyenty
Original Author

b_brae

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Gritty mix problem. How do I tell if the mix is too wet ?

Comments (4)

nguyentyOriginal Author

b_brae

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tapla (mid-Michigan, USDA z5b-6a)

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nguyenty
Original Author