I am going to experiment this year with my mix to try to accomplish these goals:

Reduce compaction

Increase aeration

Keep the weight low

Keep costs low too

Lower water retention of mix vs. Pro-mix only

The ingredients I found semi-local to me:

Co-op Growers-

Pro-mix BX 3.8 cu ft $27.99

Pro-mix BRK 2.8 cu ft $14.99

Coarse Perlite 20lbs $20ish

Coarse Vermiculite 20lbs $20ish

John Deere-

Turface All Sport 50lbs $16.80(think I can do better)

Pine Bark Fines????? I can't find them fine enough so I might use Pro-mix BRK

I am going to mix it up so actual peat will be about 1/4-1/2 of total mix. I mads some tonight and it looks promising. I will take pictures of the mix and raw materials tomorrow. The compaction and weight is already better than fully saturated Pro-mix.

Does anybody want to share some mix recipes that meet my criteria?

That's just what I need! I was looking at their website and I want to try the cocoa shell mulch as a top dressing too.

The cocoa shell mulch is a problem if you have dogs.  They're attracted to it, eat it and it can kill them.  They can't metabolize methylxanthines the way we can so caffeine and theobromine are toxic to them.

My new current recipe on trial is:

Licorice Mulch(Couldn't find Pine bark fines and I like what I read)

Pro-mix BX

Chunky perlite

Turface

Chunky Vermiculite(I saw your post James but I have a massive bag in the garage)

Pine bark nuggets at the bottom of the pot to keep the mix from running out since it is so loose.

As far as turface on the bottom and vermiculite on top, I believe it's too moisture retentive.  The only reason I use turface with perlite is because the turface is a little finer and holds a little more moisture than straight perlite.

@Brent- I never thought of using two mixes in the same pot.

This is a picture of one of my current formulas. It is 2/3 turface, perlite, and vermiculite. the other 1/3 is pro-mix and licorice bark.

I am still searching for Pine Bark fines in South Jersey.

Thanks, that place does not seem that bad to get to from me. I'm still hoping to find a closer source... I am shocked at how hard it is to find this stuff.

i've been using some pine bark mix with compost, perlite and peat moss at 5:1:1 ratio since i started growing fig. it works nice, but the roots grow too quick. i might go to potting mix (off the shelf stuff like miracle grow) and perlite 1:1.

pete

Hi, guys. Over the years, I've done a LOT of experimenting with soils, including side by side tests of soils made with CHCs and coir in the stead of pine bark and peat respectively. In all cases, the plants grown in the CHCs and coir did NOT fare well in comparison, so I wouldn't be too quick to conclude that coir and CHCs are suitable substitutes for peat and pine bark, respectively, on a volume:volume basis.

Coir and peat are approximately equal in their structural stability and their water release/retention curves, but there is little comparison between the longevity of CHCs vs pine bark, with pine bark getting the nod by a considerable margin when it comes to structural stability.

Commercial growers generally limit their inclusion of both CHCs and coir to 10% or less of the medium. The reasons are, both are often processed in salt water and can have high levels of soluble salts, as well as being extremely high in K (potassium).

While it's true that pine bark that has been composted under anaerobic (airless) conditions can be quite low in pH, it's probably not any cause for concern. I've been using pine bark in my soils for at least 25 years, and I can say I've never had a bad batch. I wouldn't even guess at the number of different packagers of the product there might have been, but it's a considerable number ..... probably at least 50, and no problems.

In the end (or the beginning), ;-) your soil is the foundation your plantings are built on, and the most significant factor that determines how strong that foundation is is aeration/drainage. Inextricably included in that consideration is how much perched water soils hold; and what determines the amount of perched water held by a soil is particle size. The finer the particles, the more perched water the soil holds ..... and perched water kills.

The fine roots that do all the work die very quickly when subjected to anaerobic conditions. As the dead root tissue decays, it also generates sulfurous gas compounds, methane, and CO2, none of which are desirable in the rhizosphere (root zone). The more you can reduce the amount of perched water a soil holds, the greater will be the opportunity for a healthy and efficiently functioning root system. Even if the soggy conditions are alleviated before serious root rot sets in, root function is impaired as long as they lack sufficient oxygen in the rhizosphere.

Even if there is no visible indications that plants grown in soils that support significant amounts of perched water, there is lost potential. When the fine roots that are the plant's work horses are killed by airless conditions, or their function is impaired, the plant has to not only expend the extra energy it might have put into growth/fruit/other energy sinks to regrow the lost roots, it also is deprived of the current energy/growth/production it might have been able to realize if root function wasn't impaired.

Building aeration and drainage into soils, and reducing the ht of the PWT, hinges on particle size, and you aren't going to be able to achieve the goal when your soil has significant fractions of small particulates, like peat, coir, compost, topsoil, .....

Consider a jar filled with fine sand as representative of a soil based on fine particulates, then ask yourself what volume of BBs would be needed to turn that sand into something you would consider to be well aerated?? In your mind's eye, you can 'see' that 30-40-50-60% BBs will still leave you with a soil whose interparticulate (potential) air space is clogged with sand. Until the BBs are about 80% of the BB/sand mix, you don't see any increase in aeration/drainage (flow-thru rate) or the ht of the PWT. This example clearly illustrates why you can't start with a large fraction of fine particulates, like most commercially prepared soils, and amend them with 10-20% pine bark or perlite and hope to get much benefit. All the perlite does, until it's a very large fraction of the soil, is take up space that might otherwise be occupied by water. It doesn't increase aeration, drainage, or reduce the ht of the PWT UNLESS, in combination with other larger particles, it makes up a very large fraction of the soil.

In the end, you can almost say that as long as you don't go too far and you use a little reason in interpreting what I'm saying now, the more aeration you can build into your soils, the greater the likelihood your plants will be able to grow to their genetic potential. From the plant's perspective, the more aeration the better. The grower might view from the perspective of convenience though, rather than plant health. The grower may say, "I don't want to be saddled with watering every second or third day - even every day if it comes down to that." That's fine, we all order our priorities, but using soils that extend watering intervals comes with a price; that, in lost potential.

I often have people say, "I can only water weekly but I want to use the gritty mix. How can I adapt it to work for me. The answer is, "You can't." The gritty mix, and to some degree, the 5:1:1 mix are made with plant health in mind - not grower convenience. You would apply the concept behind each of those soils in the same way. Do I want to maximize plant vitality/growth, or do I want to minimize the effort I expend maintaining my plants. What's important isn't what compromise you end up making; rather, it's knowing there is a compromise in play. I never care what choices people make, only that they get the information to make informed choices.

I hope everyone has had a good weekend. It's been in the 20s at night here, so I've been running carts of trees in and out from under cover as temps allow.

Al        

I'm fine with having my credibility judged based on my own explanations and the grower's ability to reason. I've been studying soils and explaining to others how they work for more than 25 years, and have helped thousands become better growers in both public and forum settings for at least 10 years. I was recently (August) invited to address a group of specialty growers at a U of M's Matthaei Botanic Gardens, and that went rather well. I lecture widely on soils and various forms of container culture to various clubs & groups. The only person I really seem to have any problem with is a guy named Dan, who rears his head from time to time because he can't resist. Hopefully, that's all water under the bridge, though.

I wonder how many are willing to 'just soak their coir in distilled water a couple of times after they've checked its electrical conductivity' when peat is far less expensive out of the chute, doesn't require the extra time and expense, and doesn't have the inherent problems coir has? Also, coir usually has a near neutral pH, which makes getting Ca & Mg to the plant a common problem because liming coir based soils moves pH out of the 'sweet spot' you noted for MINERAL soils; most soluble fertilizers lack Ca & Mg. The 'sweet spot' for container media is about a full number lower on the logarithmic pH scale (closer to 5.2 than 6.2 - charts for comparison furnished on request), which means that not only would there be no room for the use of lime in coir based soils (except for plants that prefer high pH levels), but there would also be no room for the normal upward creep in pH that accompanies aging soils watered from municipal water supplies. This is all common knowledge for those with a basic understanding of soil science.

Al

The calcined DE (diatomite) shouldn't be too expensive. It can be had as NAPA Floor Dry from any NAPA Auto Parts Store for about $6 for 24 qts. Actually, as I look at your mix, I see where you could simplify & improve it a little by doing away with the DE entirely. Either the DE or the Turface are redundant in that particular formulation. They both offer water retention as their primary function, so you only need one or the other. The only significant difference would be particle size & pH. The DE is neutral and Turface is about 6.2. Not enough difference to get excited about. If you used pine bark instead of the Metromix, you'd be growing in the gritty mix.

One thing that you're doing, is going to considerable length to build a gritty soil, but then you actually undo your good intentions by using small particulates in the Metromix. These small particles filter into macro-pores, turning them into pores small enough that they are holding interparticulate water, ie, perched water. If you ran a bunch of tests, you'll find that what you're growing in is hardly any different than if you were growing only in Metromix with a little perlite added. The reason I say that is, everything in your soil is very water-retentive except the granite. If you substituted perlite for the granite fraction, you'd have essentially the same amount of aeration, same flow-thru rate, and the same PWT height.

In order to truly take advantage of the gritty fraction of your soil, you need to eliminate the fine particles so there is only air, no water, between the large particles; otherwise, you're leaving 2/3 of the benefits offered by a gritty soil lying on the table. It's the PWT that kills roots and inhibits root function, and it's the fine particles in the Metromix that ensure your soil is holding a considerable amount of perched water.

Note how there are no fine particles in the gritty mix to clog macro-pores. The soil remains well-aerated from top to bottom, even at container capacity (when the soil is holding as much water as it possibly can).

Al

We all have priorities and standards that vary. What's important is that your soil satisfies the standards you've set for yourself & your plants, and it allows you to prioritize your life (talking about time constraints) in the way you deem fitting. That's looking at things from the grower's point of view, and no one should take it upon himself to order someone else's priorities ..... and from the grower's POV, 'free' is usually good. All that said, there is also a plant's POV, which is almost always the perspective from which I approach a discussion. I can say that from the plant's POV, the soil you're using will be water-retentive to the point it's assured the plants in it are growing under some limitations that are more than just minor. If all you're using is composted manure & coir as a medium, in any combination, it's a certainty the soil holds significant amounts of perched water. if you're growing conventionally, that can't help but be limiting to root health/function. It would be very helpful if you were set up to take advantage of wicks to help drain excess water from the medium, or if you employed other techniques like pot-in-pot or pot-in-trench (partially burying your containers) to take advantage of the wicking action of the earth to help drain the extra water.

Have fun - best luck.

Al