How to properly adjust Gritty mix ratio?

11 years ago

Hi all

I am relatively new to this forum and like many before me have found the info on the soil mediums for containers from Al to be incredible.

I have moved several of my citrus to 5-1-1 mix and whilst early days they seem to be going well!

I'm keen to now try the true gritty mix but have a problem. I can't get turface or equivalent here for love nor money. Well not that I can find. The closest is attapulgite kitty litter ( far away and VERY expensive shipping) or hydro ponic clay balls (I have some 4mm clay balls in the shed unused currently).

I have though established from many posts that the following ingredients are gritty mix potential. All be it a variation from the true gritty.

-Pine bark (correct size but the upper end of the typical gritty mix bark size range)
-Pumice
-Perlite
-Scoria

I grow potted citrus trees in a relatively temperate climate. Mild winters with reasonably solid rain fall and summers which don't get beyond high 20's Celsius very often.

My question is... based on the above ingredients what ratio would you suggest I mix for a modified gritty mix.

My default will be the 1-1-1 pumice/perlite/bark that greenman used a while ago and did a very helpful post on for his Moro.

I have seen Al tweak the ratio sometimes when products change from the standard so thought I'd check before charging off and making some.

If I was to use perlite/pumice/bark should I stick with 1-1-1?

Thanks in advance for any comments.

Cheers

Macca

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Comments (9)

alan_oz
11 years ago
Hi Macca
Don't give up on finding Turface in NZ.
It was eventually found here in Australia - it is used on golf courses. Talk to some golf courses or companies that provide them with landscape materials.

Regarding your proposed pumice/perlite/bark mix - I think it will hold too much water. Replace the perlite with grit if you can get it or the scoria you have on hand.
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maca9
Original Author
11 years ago
Ok thanks Alan.

I've tried some of those channels but will keep looking.

That's interesting about replacing perlite with scoria becuase I thought that turface would hold more than perlite so if anything the pumice/perlite/bark mix would hold less than the traditional gritty. Shows I'm still learning!

Cheers

Macca
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Am I reading that correctly - you are in Orange County, CA, right? If so and you're using county water then your water quality looks great to me. If I'm looking at the right report (see here) then you have pH ~8 with ~16 ppm of Mg and ~48 ppm of Ca and total alkalinity of ~120 (180 as CaCO3 equiv). Your alkalinity is on the high side but the rest of the report looks great (for plants, I wouldn't drink it). 1 tsp of FP in 1 gallon of water will give you ~6 ppm of Mg and ~25 ppm of Ca. I mention this because your water has a good ratio of Ca:Mg and it already has both in higher levels than you'd get with typical usage of the liquid fertilizer most people around here talk about. To answer your question directly: no. The mixes are not neutral. The gritty mix will be closer to 7 than the 5-1-1 (which will be more acidic) but *it doesn't matter.* The pH of your mix initially has very little to do with the pH levels your mix will maintain over time. In containers the soil pH will be determined mostly by the pH and alkalinity of the water you use and by the type of fertilizer you use and its ratio of ammonium to nitrate (*and* the rate at which the plant is taking up both of those nutrients which can vary depending on temperature, cultivar, etc). You should basically assume that the initial pH of the mix itself is of no consequence when it comes to determining the pH of your soil over the long term. You do need to pay attention to the initial pH but only because if you transplant something into the mix you want the roots to function reasonably well from the get-go. All this means is that you need to raise the pH of the bark or peat slightly so they are more friendly to transplants - the directions for doing that are built into the 5-1-1. I grow citrus trees in both mixes. Either will work for you and there are pluses and minuses to both. In terms of pH and nutrient availability you will find that the 5-1-1 is slightly more forgiving than the gritty mix. At your pH and alkalinity if you grow citrus trees in containers you will almost certainly develop Mn and Zn deficiency even if you use something like FP (which, again: you do not need to do based on your water quality). You could avoid this by acidulating your water or by using foliar applications of Manganase Sulfate and Zinc Sulfate (1.5 g per gallon and 1 g per gallon respectively - they can be mixed and applied to new growth on plants showing deficiencies). Just looking again at your water report you also have adequate/luxury levels of B, S, Cl, Na, & Cu. Nickel will be in your soil via the bark and or peat and you likely don't need to add any. All your water may be missing is: Mo, Zn, Mn, & Fe. Were I you I would use a straight 5-1-3 fertilizer and then manage the micros as needed myself. You will find it much cheaper than the usual suggestion. You could also go with Jack's Professional 25-5-15 High Performance and you wouldn't have to manage your micros as often (you will still get Zn and Mn deficiency at your pH unless you acidulate or use a serious acid reaction fertilizer - but then you will blow your NPK ratios). The cheapest and easiest option would be to use the Jack's (or another 5-1-3 with Mo and Fe) and then use the foliar sprays 1-3 times a year. If you acidulate your water I wouldn't use sulfuric - you have a ton of S in there already. Maybe citric or vinegar (don't use phosphoric, nitric is dangerous). This will be moderately expensive and moderately time consuming even with a chemical injector. Do yourself a favor and avoid the expense of Foliage Pro with your water. You will be correcting micro issues in any case and you have better Ca/Mg/S than the fertilizer can offer you anyway.
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Claire - I understand where you're coming from. If you lived closer, we'd solve the dust and weight issue by having a little screening party at my house, so you wouldn't need to worry about the dust, & so someone could carry the materials to somewhere convenient for you. ;o) Don't forget, I'm not selling a soil, only a concept. I DO think it's hard to improve on the gritty mix as an all-purpose soil. I mean ..... it's adjustable for water retention, holds good amounts of water and nutrients, is durable, almost impossible to over-water when using it, roots love it ...... what's not to like? I DO understand that it's a little heavier than other soils, and some need to work around that issue. Others have made a fuss about how quickly it drains, but jeez - fast drainage goes along with a higher degree of aeration goes along with better root health goes along with happier plants goes along with a more satisfying growing experience. I guess I always have plenty of patience with people (like you) who are trying to employ the concept within their limitations, but I tend to lose patience when people start changing things on a whim, because they 'think' something might work better. This often occurs before they've even given the soil a try, or even fully understand the whole aeration/PWT/drainage concept. I don't mean I get upset, it's just that I realize I'm banging my head against a wall and it feels better when I quit. ;o) "Now it's dawning on me that the water in the clay is also "water retention" and possibly, in excess, as bad for the plant as the PWT. Have I got that right?" Not quite right yet. Plants don't 'drink' water, they absorb it a molecule at a time - in the form of vapor and from the thin film on colloidal surfaces in the soil. Water held in internal pores of particles like bark and Turface provide a healthy reservoir of moisture the plant can use. When soil particles are uniform and large enough that the soil holds little or no water in a PWT, the rhizosphere (roots and soil) is a happy place. Root function and metabolism proceeds at a sharp pace, within other limiting factors. When we fill part of the rhizosphere with water, root function and metabolism suffers, we experience a cyclic death and regeneration of fine roots, and we significantly increase the likelihood of root rot becoming an issue. This excess water also makes it difficult to water to our plants' best advantage and to control accumulation of soluble salts. If it was a perfect world, Turface MVP would be a little larger in particle size. Screened Turface, by itself, holds not only a lot of water, but it holds a PWT as well. Unscreened Turface holds significantly more water because of the much taller PWT (in comparison to screened MVP). This makes the PRIMARY issue the PWT. Turface gives up its moisture quickly, by diffusion when particles in the soil are large enough. The gritty mix never becomes hydrophobic (water-repellent) because the Turface always readily absorbs water. Even if the bark has become very dry and hydrophobic, wetting the Turface allows water to diffuse into the bark within a short period. If, however, you are growing in 100% unscreened Turface, the Turface becomes saturated quickly, but with gas exchange limited by particle size, air is slow to return to the soil, which is not a good thing. Perhaps you could do some research here about the larger DE available. We started out using a product from NAPA (#8822), but someone discovered that a CarQuest product was larger and more uniform. Calcined DE is lighter than Turface, too. You may find this is where your search for something that will give you the aeration/drainage you're looking for would be most productive. Try this thread for more info, Claire. Take care. Al
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If you pour it all into a tray full of water the oil dry should sink and the bark/perlite should float (which I would toss)? Perlite holds a lot of water, much more than grit. So in theory I think it can replace the bark in soil mixes (especially if bark is expensive). However, you then end up relying on the oil dry to hold all the nutrients (if you fertilize). Doesn't seem like many of us are using the grit/turface/perlite combo except Rina? I think she's onto something there but I don't know what ratios are best to use. I have a pot of her mix but I'm too reluctant to just dump it out! Plus, it works well. I've made two grit/perlite pots (20% grit : 79% perlite : 1% soil) which I'm growing my Schlumbergera cuttings in. They seem to be working alright so far. The rest of my pots use some amount of repti-bark. I'm a long way from decomposition as my mix is fairly new.
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JerryVentura Jordan
11 years ago
I live in Southern California, mild most of the time, windy here on the coast. I figure everyone adjust according to what works for them, trial and error. I grow citrus, herbs, plumeria, fuchsia, natives, ferns, really anything I buy that's goes into a container, I put in equal parts bark, turface and pumice. I water twice a week unless we are having hot dry winds, or more often for first year plantings. My house plants are bark, turface, perlite, but as I re pot I'm going to change to pumice. This works for me and my situation.
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maca9
Original Author
11 years ago
Hey Jerry. Thanks for your comments.

I guess my key question is, in the absence of turface should I stick with 1-1-1 relationship?

The way I understand what I've read the following applies to the gritty mix and my ingredients.

- you need 1/3 bark (max organic material)

- turface holds more water than perlite or pumice

- perlite or pumice holds more water than granite

So on this logic (if its correct) then maybe the 1-1-1 with my ingredients (copying Greenmans moro mix) is the most similar to the true gritty in the absence of Turface due to perlite and pumice in combination having similar water retention to turface and granite combined?

Or have I got this wrong and due to not having turface then the perlite/pumice relationship should be different from 1/1.

Very interested to hear comments from those with much more knowledge on the above.

Cheers

Macca
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sutremaine
11 years ago
Whatever your final mix is, aim for it to be 60-75% air when dry and equal parts air, water, and solids when saturated and drained off. It's not the specific ingredients in the gritty mix that make it work, it's what those ingredients do for air and moisture retention.
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greenman28 NorCal 7b/8a
11 years ago
Hello!

Macca, I think my Moro mix has a larger fraction of screened bark - 4 or 5 parts bark, I'd guess. Sorry for the confusion. Probably about 2 parts of Scoria (which holds less moisture than Turface or Pumice). And at least 1 part coarse Perlite. Let me run out back and snap a quick pic....

Josh
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greenman28 NorCal 7b/8a
11 years ago
I'm back....
here's a pic of my gritty 5-1-1 - screened bark, no fine bark dust. At first, this made for a very fast-draining mix - but now that it has aged, the mix holds moisture better. During the Winter, indoors, I water about once a week - during the Summer, outdoors, I water twice a week.
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maca9
Original Author
11 years ago
Hey Josh.

Thanks. The picture is very helpful.

I didn't realize your mix was a gritty 5-1-1 as opposed to a different ingredients 1-1-1.

I've got some trees in the traditional 5-1-1 and was hoping to try something as close as possible to the true gritty without the the turface which is unavailable here.

I understand from one of Al's posts that to have a true gritty you need max 1/3 bark or there is too much organic material and therefore not as long term or durable.

I'm gonna try a mix of

1/3 bark
1/3 perlite
1/3 pumice

plus gypsum

And see how that goes.

Whilst it might not be as good as the true gritty I'm sure it will be considerably better than an off the shelf mix and more durable than the 5-1-1.

Im putting a variegated calamondin in the mix.

I'll let you all know how it goes.

Cheers

Macca
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nil13
11 years ago
4mm clay balls. That's a little bigger than 1/8". That actually sounds pretty close to turface. I think those would work really well. I've never seen them that small. The ones I see are usually more like 15mm which is too big for this purpose.
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How to properly adjust Gritty mix ratio?

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How to properly adjust Gritty mix ratio?

Comments (9)

alan_oz

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