Tapla - Question About Container Soil For Transplant

Flower Mound, TX

I have been digging through all your posts around soil composition, etc. Also just finished reading Teaming With Microbes, which is an incredibly educational book.

My immediate question involves transplanting several dwarf blueberry plants to half-whiskey barrel sized planters. In advance of transplanting, a couple of months ago I put some acid oriented plant mix in the containers (Calloways bagged planting mix for azaleas, etc). Over time I have supplemented the mix with pine bark compost and lava sand. My hope is that the lava sand provides additional aeration, etc.

In a separate bucket, I'm also "baking " some brown compost with alfalfa meal and baby oatmeal with the intent of making some fungal-oriented compost tea to douse the container soil with. I learned from the Teaming book that perennials like the fungal rich soil.

Sorry for the diatribe, but my real question is, is there anything else I need to supplement my container soil with to ensure long term aeration and sustainability?



Bay City, MI(Zone 6a)

I'm going to ask a question that is posed to make you consider the paradox in your own question. Don't take it as though I'm being judgmental - it's not like that. I'll gladly help you as much as I can.

The question is: Why worry about aeration and drainage when you're adhering to practices that are going to ensure issues in that area? My GUESS, by the sound of the title, is it's a book about gardening in the earth. If so, trying to apply that information to container culture is like reading a book about auto mechanics when you're trying to repair your bicycle.

If you consider for a moment, that the more you 'feed' and build up the microbial population in the container medium, the faster that population collapses (breaks down) the soil into increasingly smaller particles. You literally end up with a soupy medium that, in large part, you brought about by your own methodology. This puts you in something of a race. You have to hope you can grow your plants to a point they are mature enough that they, in combination with evaporation, can use the large volume of water in the soil fast enough to prevent root rot, or other issues associated with the anaerobic conditions all soils that support perched water produce, these being primarily reduced root function/metabolism and the production of noxious gasses like CO2 (we want lots of O2 in the rhizosphere, not CO2) sulfurous compounds, methane. Even if you do grow your plants to a mature state and the roots do colonize the entire container, if the soil is supporting any perched water for more than a few hours, you're getting a cyclic death (when soggy) & regeneration (when air returns) of roots that requires energy that would otherwise have gone to blooms, fruit, increasing the mass of the plant - to a desired bio-function. When I discovered this issue is when I started looking closely at container media and contemplating how to work AROUND it, instead of with it.

Setting that aside - It's not that your blueberries love an acid soil - they simply cannot effectively limit their uptake of Ca. If you could keep Ca levels low enough, you could easily grow your BBs at a MEDIA pH of 8.0+. Low pH limits Ca availability, so in practical situations where the Ca supply can't realistically be limited, you see BBs growing in soils well on the acidic side. In container culture, the pH of the soil solution is much more important than media pH. Since it's not practical for a hobby grower to try to manage pH in such a way to keep it at any particular level, I suggest you turn to your fertigation solution & manage pH by adjusting that.

Before I go any further, and so I can be sure I'm not wasting my breath, I suppose it would be smart to find out if you're tied to an all-organic approach? There's a big difference between working with what you have & working around it. Blueberries are like potatoes - they love lots of water but don't like wet feet - which is why blueberry 'bogs' are usually found in sandy soil where the water table is close to the surface. The nutrition part is easy, but how about your thoughts on the medium?


Flower Mound, TX

You're making sense. I think the Teaming book is more about long term microbial support in an open soil where the buildup of dead organisms would not be such an issue. Never thought about what the microbe lifecycle would do in a closed environment.

Based on that, for my containers, I'm not hung up on an organic approach. I do believe in trying to naturally build up the soil in my beds, but can see where that approach may not be practical for containers.

So, what mix would you recommend for a container bound blueberry?

And again, thanks for the info you share here. Worth more than most any gardening book I've seen.

Bay City, MI(Zone 6a)

That was a nice compliment, JD. Thank you for the kind words.

So there is no question I'm not a chemical freak - I maintain a nearly all organic approach in my gardens & beds. I use compost & OM to improve the soil, so I rarely need to fertilize. I put some effort into choosing the right plant for the right place, so I rarely have to contend with disease or insects. When I do, I practice IPM principles.

Containers are different. I can help almost anyone grow in a well-aerated soil using soluble fertilizers, but when it comes to using an all organic approach, there is very little specific advice anyone can give, beyond that which helps them try to cope. The reason I can say that is the number of variables it's necessary to contend with when using well-aerated soils and soluble fertilizers is very small compared to the number of variables involved with an all organic approach. Not only are the number of variables greater, but the potential for problems grows exponentially with the number of variables.

An example might be: "I'm growing in the gritty mix (a highly aerated soil with 1/3 bark and the other 2/3 inorganic mineral components) and I have yellow leaves." Immediately, I can eliminate 3/4 of the likely problems issuing from the soil. If you had said I'm growing in a medium made from compost, sand, and peat, I would need to eliminate several soil-related possibilities before I could move on to exploring nutrition. If you're using a well-aerated soil and say a 10-30-10 bloom booster fertilizer, I might quickly zero in on the excess P and how it inhibits uptake of N, Fe, and Mn. I could tell you to simply switch to a 3:1:2 ratio fertilizer, based on good science. If you're using the compost-based soil with a handful of this and that to supply nutrients, I have absolutely no idea where the yellowing has come from, and neither would anyone else. You'll end up with a dozen opinions and a dozen remedies to choose from, based on ....... I guess I can't guess.

Getting back to nutrition. Using a soluble fertilizer, you know EXACTLY what your plant is getting and when they are getting it. This helps tremendously in simplifying your formulation of a nutrient supplementation plan. Looking at the flip side, we can try to supply nutrients by adding things like bone meal, blood/hoof/feather/alfalfa or other meals and soil amendments, but realistically, we have very little clue, or control, over how much of what our plants are getting, or when they are getting it. Since all the nutrients supplied by these soil amendments are locked securely in hydrocarbon chains, the chains must be cleaved by soil microbes and the molecules broken down into elemental form before they can pass into the plant. The elements that pass through cell walls are exactly the same, whether from organic sources or from soluble fertilizers. The plants don't know, or care, where the elements come from - only people do. Since containers are very unfriendly environments for soil life, a measure their numbers can usually be described as boom/bust. This makes delivery of nutrients from soil amendments erratic and unreliable when compared to soluble fertilizers.

Finally, getting to your question, I would suggest a durable soil you can water freely w/o the risk of it remaining saturated for extended periods. There are a couple of recipes offered as starting points in the link I'll leave, though most people choose to follow them as closely as possible until they get their footing. Keep in mind, I'm not selling a soil recipe, I'm selling a concept, that being: Keep aeration and durability in mind when you choose a container soil. It's very unimportant what a soil is made from, as long as it provides the PHYSICAL properties that favor the plant. Starting with large particles and adding a small amount of smaller particles to adjust to the water retention you need, is much easier/better than starting with small particles and trying to correct excess water retention by adding perlite or other large particles.

I'll listen to what you have to say, then we can talk about nutrition if you like.


Flower Mound, TX

Thanks Al. Didn't see the link you mentioned, but what I am hearing is that maybe I stick with plant mix I currently have in the containers, supplementing generously with some pine bark mulch and maybe permalite and lava sand to create a "large particle" type of soil. And I would think layering some brown-based compost/mulch on top would also provide some long term feeding and moisture retention.

Love to hear your thoughts on more immediate nutrition. I've always been taught to use the low number fertilizers like a 5:5:5 or something similar.

Am I on the right track? Again this is for blueberries, and based on your earlier comments, I'm not sure I have to do much more than use some pine mulch, etc to build the soil the plants will thrive in. Should I stick with a genral fert, or something that is tailored for "acid loving" plants?

Thanks ..

SE Houston (Hobby), TX(Zone 9a)

I think this is the thread Al's directing you to. He and I have been discussing this subject for two weeks or longer.

The key is to start with LARGE particles, then add your smaller particle medium to that. You wanna aim for a 50% fraction (ratio/part/portion) of large particles (at least BB size pine bark fines, soil conditioner, etc.) to small particle medium. Add your existing small particle medium bit-by-bit up to a 50% fraction (ratio), until you get the water retention and drainage action you need.

The larger, STABLE particles won't break down and collapse like a larger fraction organic foundation will. Once you've built your stable soil, you can add organics till the cows come home (and deposit more organics), and your soil won't compact or collapse. But you've got to start with a foundation that provides great aeration and good drainage.

Al will be coming along shortly to correct anything I've got wrong. Right, Al?



This message was edited Sep 4, 2010 1:41 PM

Bay City, MI(Zone 6a)

Sorry I forgot the link. Here it is: http://davesgarden.com/community/forums/t/1073399/

I'll let you digest the material I linked to. Perhaps it will clarify what I was talking about.

As far as the 5-5-5 fertilizer: I'll be talking about % AND ratios, so when I put dashes (-) between the numbers, it means I'm referring to the %s of NPK in a fertilizer. When I put a colon (:) between the numbers, I'm talking about a RATIO. a 5-5-5 fertilizer is a 1:1:1 ratio. The % #s on a fertilizer box are pretty insignificant because you always end up adjusting the amount of fertilizer given by the dose/solution concentration.

Let's just say Brand-X suggests 2 tsp of 30-10-20 per gallon of water, which would make 1,346 ppm solution (disregarding solutes other than NPK and dissolved solids in the water). If they also make a 15-5-10 fertilizer, they'll suggest 4 tsp per gallon because their target is around a 1,346 PPM strength solution. So you can have 2 very different NPK %s, but you're still supplying the same amount of fertilizer because you're adjusting the dose to supply a target solution strength. If the manufacturer suggested you add 1 lb of 5-5-5/100 sq ft of garden, he would suggest 1/2 lb of 10-10-10 for the same area. So you see, you'll end up supplying the same amount of fertilizer (if you follow the directions) whether you use 5-5-5, 12-12-12, or 20-20-20 - they're ALL 1:1:1 ratios.

When you take an average of the ratio of nutrients plants actually use, you'll find only minor variance from the ratio 10:1.5:7. For every 10 parts of N they use, plants use about 1.5 parts of P and 7 parts of K. When the 3:1:2 ratio fertilizers are adjusted for actual P and K content because P is reported as P2O5 and K is reported as K20, you see that they fit this ratio almost perfectly, and it's no accident. We usually furnish nutrients based on a fraction of N, so 1:1:1 ratio fertilizers furnish much more P and K than is necessary in relation to N. This unnecessarily raised the EC/TDS (electrical conductivity/total dissolved solids - a measure of the amount of solutes in the soil solution) levels of the soil solution and makes it unnecessarily difficult for plants to absorb water and the nutrients dissolved in water. This isn't to say you can't grow healthy plants using 1:1:1 ratios like 5-5-5, 12-12-12, 20-20-20, but 3:1:2 ratios like 24-8-16, 12-4-8, and 9-3-6 (Foliage-Pro 9-3-6 is my choice) are better choices and provide a wider margin for error. You can keep EC/TDS levels at the lowest possible w/o deficiencies - a decided advantage.


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