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Tapla's 5-1-1 Container Mix in More Detail

posted by: goodhumusman on 02.26.2009 at 12:44 pm in Container Gardening Forum

I recently joined the forum and discovered Al's 5-1-1 Mix, but I had several questions that Al was kind enough to answer by email. I also found the answers to other questions in several different threads. I thought it would be useful to organize all of the info in one place so that we could have easy access to it. 98% of the following has been cut/pasted from Al's postings, and I apologize in advance if I have somehow misquoted him or taken his ideas out of proper context. The only significant addition from another source is the Cornell method of determining porosity, which I thought would be germane. I have used a question and answer format, using many questions from other members, and I apologize for not giving them proper credit. Thanks to all who contributed to this information. Now, here's Al:

Tapla's 5-1-1 Mix

5 parts pine bark fines
1 part sphagnum peat
1-2 parts perlite
garden lime
controlled release fertilizer (not really necessary)
a micro-nutrient source (seaweed emulsion, Earthjuice, Micro-max, STEM, etc,)

Many friends & forum folk grow in this 5-1-1 mix with very good results. I use it for all my garden display containers. It is intended for annual and vegetable crops in containers. This soil is formulated with a focus on plentiful aeration, which we know has an inverse relationship w/water retention. It takes advantage of particles, the size of which are at or just under the size that would guarantee the soil retains no perched water. (If you have not already read Al's treatise on Water in Container Soils, this would be a good time to do so.) In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they starve/"suffocate" because there is insufficient air at the root zone to ensure normal water/nutrient uptake and root function.

I grow in highly-aerated soils with the bulk of the particles in the 1/16"-1/8" size, heavily favoring the larger particles, because we know that perched water levels decrease as particle size increases, until finally, as particle size reaches just under 1/8" the perched water table disappears entirely.

Ideal container soils will have a minimum of 60-75% total porosity. This means that when dry, in round numbers, nearly 70% of the total volume of soil is air. The term 'container capacity' is a hort term that describes the saturation level of soils after the soil is saturated and at the point where it has just stopped draining - a fully wetted soil. When soils are at container capacity, they should still have in excess of 30% air porosity. Roughly, a great soil will have about equal parts of solid particles, water, and air when the soil is fully saturated.

This is Cornell's method of determining the various types of porosity:

To ensure sufficient media porosity, it is essential to determine total porosity, aeration porosity, and water-holding porosity. Porosity can be determined through the following procedure:

* With drainage holes sealed in an empty container, fill the container and record the volume of water required to reach the top of the container. This is the container volume.

* Empty and dry the plugged container and fill it with the growing media to the top of the container.

* Irrigate the container medium slowly until it is saturated with water. Several hours may be required to reach the saturation point, which can be recognized by glistening of the medium's surface.

* Record the total volume of water necessary to reach the saturation point as the total pore volume.

* Unplug the drainage holes and allow the water to freely drain from the container media into a pan for several hours.

* Measure the volume of water in the pan after all free water has completed draining. Record this as the aeration pore volume.

* Calculate total porosity, aeration porosity, and water-holding porosity using the following equations (Landis, 1990):

* Total porosity = total pore volume / container volume
* Aeration porosity = aeration pore volume / container volume
* Water-holding porosity = total porosity - aeration porosity

The keys to why I like my 3-1-1 mix:

It's adjustable for water retention.
The ingredients are readily available to me.
It's simple - 3 basic ingredients - equal portions.
It allows nearly 100% control over the nutritional regimen.
It will not collapse - lasts longer than what is prudent between repots.
It is almost totally forgiving of over-watering while retaining good amounts of water between drinks.
It is relatively inexpensive.

Q. Why do you use pine bark fines? Bark fines of fir, hemlock or pine, are excellent as the primary component of your soils. The lignin contained in bark keeps it rigid and the rigidity provides air-holding pockets in the root zone far longer than peat or compost mixes that too quickly break down to a soup-like consistency. Conifer bark also contains suberin, a lipid sometimes referred to as nature�s preservative. Suberin, more scarce as a presence in sapwood products and hardwood bark, dramatically slows the decomposition of conifer bark-based soils. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains.

Q. What is the correct size of the fines? In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they starve/"suffocate" because there is insufficient air at the root zone to insure normal water/nutrient uptake and root function.Pine bark fines are partially composted pine bark. Fines are what are used in mixes because of the small particle size. There will be a naturally occurring "perched water table" (PWT) in containers when soil particulate size is under about .125 (1/8) inch, so best would be particulates in the 1/16 - 3/16 size range with the 1/16-1/8 size range favored.

Note that there is no sand or compost in the soils I use. Sand, as most of you think of it, can improve drainage in some cases, but it reduces aeration by filling valuable macro-pores in soils. Unless sand particle size is fairly uniform and/or larger than about � BB size I leave it out of soils. Compost is too unstable for me to consider using in soils. The small amount of micro-nutrients it supplies can easily be delivered by one or more of a number of chemical or organic sources.

Q. Do you use partially composted pine bark fines? Yes - preferred over fresh fines, which are lighter in color.

Q. I found some Scotchman's Choice Organic Compost, which is made of pine bark fines averaging about 1/8" in size, and, after adding all ingredients, the 5-1-1 Mix had a total porosity of 67% and an aeration porosity of 37%. Is that all right? Yes, that is fine.

Q. What kind of lime do you use? Dolomitic.

Q. What amount of lime should I add if I used 10 gal of pine bark fines and the corresponding amount of the other ingredients? @ 5:1:1, you'll end up with about 12 gallons of soil (the whole is not equal to the sum of the parts when you're talking about soils), so I would use about 10-12 Tbsp or 2/3-3/4 cup of lime.

Q. What grade of coarseness for the lime? Most is sold as garden lime, which is usually prilled powder. Prilling makes it easier to use in drop & broadcast spreaders. The prills dissolve quickly. The finer the powder the quicker the reactive phase is finished. Much of the Ca and Mg will be unavailable until the media pH equalizes so the plant can assimilate the residual elements. Large pieces of lime really extend the duration of the reactive phase.

Q. Does this mean that I need to make up the soil in advance? Yes. 2 weeks or so should be enough time to allow for the reaction phase to be complete & residual Ca/Mg to become more readily available from the outset .

Q. During those 2 weeks, do I need to keep turning it and moistening it? No

Q. Can I go ahead and fill my 3-gal. containers, stack them 3-high, and cover the top one to prevent moisture loss during the waiting period? Something like that would be preferred.

Q. The perlite I use has a large amount of powder even though it is called coarse. Do I need to sift it to get rid of the powder? Not unless it REALLY has a lot - then, the reason wouldn't be because of issues with particle size - it would be because you had to use larger volumes to achieve adequate drainage & larger volumes bring with it the possibility of Fl toxicity for some plants that are fluoride intolerant.

Q. What about earthworm castings (EWC)? I think 10% is a good rule of thumb for the total volume of fine particles. I try to limit peat use to about 10-15% of soil volume & just stay away from those things that rob aeration & promote water retention beyond a minimal perched water table. If you start adding 10% play sand, 10% worm castings, 10% compost, 10% peat, 10% topsoil, 10% vermiculite to a soil, before long you'll be growing in something close to a pudding-like consistency.

Q. Do you drench the mix with fertilized water before putting in containers? No - especially if you incorporate a CRF. It will have lots of fertilizer on it's surface & the soil could already be high in solubles. If you added CRF, wait until you've watered and flushed the soil a couple of times. If you didn't use CRF, you can fertilize with a weak solution the first time you water after the initial planting irrigation.

Q. How much of the micronutrients should I add if I am going to be fertilizing with Foliage Pro 9-3-6, which has all the micronutrients in it? You won't need any additional supplementation as long as you lime.
Q. Just to make sure I understand, are you saying I don't need to use Foliage Pro 9-3-6 until after the initial watering right after planting even if I don't use a CRF? And no additional micronutrients? That's right - on both counts.

Q. Do I need to moisten the peat moss before mixing with the pine bark fines? It helps, yes.

Selections from Notes on Choosing a Fertilizer

A) Plant nutrients are dissolved in water
B) The lower the nutrient concentration, the easier it is for the plant to absorb water and the nutrients dissolved in the water - distilled water is easier for plants to absorb than tap water because there is nothing dissolved in distilled water
C) The higher the nutrient content, the more difficult it is for plants to absorb water and the nutrients dissolved in water
D) To maximize plant vitality, we should supply adequate amounts of all the essential nutrients w/o using concentrations so high that they impede water and nutrient uptake.

All that is in the "Fertilizer Thread" I posted a while back.

Q. Do you use the Dyna-Gro Foliage Pro 9-3-6 exclusively throughout the life of the plant, or change to something else for the flowering/fruiting stage? I use lots of different fertilizers, but if I had to choose only one, it would likely be the FP 9-3-6. It really simplifies things. There are very few plants that won't respond very favorably to this fertilizer. I use fast soils that drain freely & I fertilize at EVERY watering, and it works extremely well.

If you are using a soil that allows you to water freely at every watering, you cannot go wrong by watering weakly weekly, and you can water at 1/8 the recommended dose at every watering if you wish with chemical fertilizers.

Q. What about the "Bloom Booster" fertilizers? To induce more prolific flowering, a reduced N supply will have more and better effect than the high P bloom formulas. When N is reduced, it slows vegetative growth without reducing photosynthesis. Since vegetative growth is limited by a lack of N, and the photosynthetic machinery continues to turn out food, it leaves an expendable surplus for the plant to spend on flowers and fruit. There are no plants I know of that use anywhere near the amount of P as they do N (1/6 is the norm). It makes no sense to me to have more P available than N unless you are targeting a VERY specific growth pattern; and then the P would still be applied in a reasonable ratio to K.

Somewhere along the way, we curiously began to look at fertilizers as miraculous assemblages of growth drugs, and started interpreting the restorative effect (to normal growth) fertilizers have as stimulation beyond what a normal growth rate would be if all nutrients were adequately present in soils. It�s no small wonder that we come away with the idea that there are �miracle concoctions� out there and often end up placing more hope than is reasonable in them.

What I'm pointing out is that fertilizers really should not be looked at as something that will make your plant grow abnormally well - beyond its genetic potential . . . Fertilizers do not/can not stimulate super growth, nor are they designed to. All they can do is correct nutritional deficiencies so plants can grow normally.

Q. Should I use organic ferts or chemical ferts in containers? Organic fertilizers do work to varying degrees in containers, but I would have to say that delivery of the nutrients can be very erratic and unreliable. The reason is that nutrient delivery depends on the organic molecules being broken down in the gut of micro-organisms, and micro-organism populations are boom/bust, varying widely in container culture.

Some of the things affecting the populations are container soil pH, moisture levels, nutrient levels, soil composition, compaction/aeration levels ..... Of particular importance is soil temperatures. When container temperatures rise too high, microbial populations diminish. Temps much under 55* will slow soil biotic activity substantially, reducing or halting delivery of nutrients.

I do include various formulations of fish emulsion in my nutrient program at certain times of the year, but I never rely on them, choosing chemical fertilizers instead. Chemical fertilizers are always immediately available for plant uptake & the results of your applications are much easier to quantify.

Q. Should I feed the plants every time I water? In a word, yes. I want to keep this simple, so I�ll just say that the best water absorption occurs when the level of solutes in soil water is lowest, and in the presence of good amounts of oxygen. Our job, because you will not find a sufficient supply of nutrients in a container soil, is to provide a solution of dissolved nutrients that affords the plant a supply in the adequate to luxury range, yet still makes it easy for the plant to take up enough water to be well-hydrated and free of drought stress. All we need to do is supply nutrients in approximately the same ratio as plants use them, and in adequate amounts to keep them in the adequate to luxury range at all times. Remember that we can maximize water uptake by keeping the concentrations of solutes low, so a continual supply of a weak solution is best. Nutrients don�t just suddenly appear in large quantities in nature, so the low and continual dose method most closely mimics the nutritional supply Mother Nature offers. If you decide to adopt a "fertilize every time you water" approach, most liquid fertilizers can be applied at � to 1 tsp per gallon for best results.

The system is rather self regulating if fertilizer is applied in low concentrations each time you water, even with houseplants in winter. As the plant�s growth slows, so does its need for both water and nutrients. Larger plants and plants that are growing robustly will need more water and nutrients, so linking nutrient supply to the water supply is a win/win situation all around.

You can tell you've watered too much (or too little - the response is the same - a drought response) when leaves start to turn yellow or you begin to see nutritional deficiencies created by poor root metabolism (usually N and Ca are first evident). You can prevent overwatering by A) testing the soil deep in the container with a wood dowel ... wet & cool - do not water, dry - water. B) feeling the wick & only watering when it's dry C) feel the soil at the drain hole & only water when it feels dry there.

Soils feel dry to our touch when they still have 40-45% moisture content. Plants, however, can still extract water from soils until they dry down to about 25-30%, so there is still around a 15% cush in that plants can still absorb considerable moisture after soils first feel dry to us.

Q. When you water/fertilize, do you give it enough that 10% leaches out the bottom each time? Yes, I try to do that at every watering. Remember that as salts accumulate, both water and nutrient uptake is made more difficult and finally impaired or made impossible in severe cases. Your soils should always allow you to water so that at least 10-15% of the total volume of water applied passes through the soil and out the drain hole to be discarded. This flushes the soil and carries accumulating solutes out the drain hole. In addition, each thorough watering forces stale gases from the soil. CO2 accumulation in heavy soils is very detrimental to root health, but you usually can't apply water in volume enough to force these gases from the soil. Open soils allow free gas exchange at all times.

Q. Should I elevate my pots? The container will not drain the same % of water if it's sitting in a puddle, but the % won't be particularly significant. What will be significant is: if water (in a puddle) is able to make contact with the soil in the container through surface tension and/or capillarity, it will "feed" and prolong the saturated conditions of any PWT that might be in the container. However, if water can soak in or if it will flow away from the containers, there's no advantage to elevating when you're not using a wick.

Q. I like a pH of about 5.7. Is that about right? That's a good number, but you won't have any way of maintaining it in your soil w/o some sophisticated equipment. I never concern myself with media pH. That doesn't mean you should ignore water pH, though. It (water pH) affects the solubility of fertilizers; and generally speaking, the higher the water pH, the lower the degree of nutrient solubility.

Q. How do you repot? Some plants do not take to root-pruning well (palms, eg), but the vast majority of them REALLY appreciate the rejuvenational properties of major root work. I'm not at all delicate in my treatment of rootage when it comes time to repot (completely different from potting-up). Usually I chop or saw the bottom 1/2-2/3 of the root mass off, bare-root the plant, stick it back in the same pot with ALL fresh soil, use a chopstick to move soil into all the spaces/pockets between roots, water/fertilize well & put in the shade for a week to recover. I should mention that this procedure is most effective on plants with woody roots, which most quickly grow to be inefficient as they lignify, thicken, and fill the pot. Those plants with extremely fibrous root systems are easier to care for. For those, I usually saw off the bottom 1/2 - 2/3 of the roots, work a chopstick through the remaining mat of roots, removing a fair amount of soil, prune around the perimeter & repot in fresh, well-aerated soil.

I find that time after time, plants treated in this fashion sulk for a week or two and then put on a huge growth spurt (when repotted in spring or summer). Growth INVARIABLY surpasses what it would have been if the plant was allowed to languish in it's old, root-bound haunts. Potting up is a temporary way to rejuvenate a plant, but if you look ate a long-term graph of plants continually potted-up, you will see continual decline with little spurts of improved vitality at potting-up time. This stress/strain on plants that are potted-up only, eventually takes its toll & plants succumb. There is no reason most houseplants shouldn't live for years and years, yet we often content ourselves with the 'revolving door replacement' of our plants when just a little attention to detail would allow us to call the same plant our friend - often for the rest of our lives if we prefer.

Q. Is there any rule of thumb as to how often to root prune? I'm going to answer as if you included 'repotting' in your question. There is no hard, fast rule here. Some of you grow plants strictly for the blooms, and some plants produce more abundant blooms in containers when they are stressed in some manner. Often, that stress is in the form of keeping them root-bound. I'll talk about maintaining a plant's vitality & let you work out how you want to handle the degree of stress you wish to subject them to, in order to achieve your goals. Before I go on, I'd like to say that I use stress techniques too, to achieve a compact, full plant, and to slow growth of a particularly attractive plant - to KEEP it attractive. ;o) The stress of growing a plant tight can be useful to a degree, but at some point, there will be diminishing returns.

When you need to repot to correct declining vitality:

1) When the soil has collapsed/compacted, or was too water-retentive from the time you last potted-up or repotted. You can identify this condition by soil that remains wet for more than a few days, or by soil that won't take water well. If you water a plant and the soil just sits on top of the soil w/o soaking in, the soil has collapsed/compacted. There is one proviso though: you must be sure that the soil is wet before you assess this condition. Soils often become hydrophobic (water repellent) and difficult to rewet, especially when using liquid organic fertilizers like fish/seaweed emulsions. Make sure this effect is not what you're witnessing by saturating the soil thoroughly & then assessing how fast the water moves downward through the soil. The soils I grow in are extremely fast and water disappears into the mix as soon as it's applied. If it takes more than 30 seconds for a large volume of water to disappear from the surface of the soil, you are almost certainly compromising potential vitality.

I'll talk about the potential vitality for just a sec. Plants will grow best in a damp soil with NO perched water. That is NO saturated layer of water at the bottom of the pot. Roots begin to die a very short time after being subjected to anaerobic conditions. They regenerate again as soon as air returns to the soil. This cyclic death/regeneration of roots steals valuable energy from the plant that might well have been employed to increase o/a biomass, and/or produce flowers and fruit. This is the loss of potential vitality I refer to.

2) When the plant is growing under tight conditions and has stopped extending, it is under strain, which will eventually lead to its death. "Plants must grow to live. Any plant that is not growing is dying." Dr. Alex Shigo Unless there are nutritional issues, plants that have stopped extending and show no growth when they should be coming into a period of robust growth usually need repotting. You can usually confirm your suspicions/diagnosis by looking for rootage "crawling" over the soil surface and/or growing out of the drain hole, or by lifting the plant from its pot & examining the root mass for encircling roots - especially fat roots at the container's edge. You'll be much less apt to find these types of roots encircling inner container perimeter in well-aerated soils because the roots find the entire soil mass hospitable. Roots are opportunistic and will be found in great abundance at the outside edge of the soil mass in plantings with poor drainage & soggy soil conditions - they're there looking for air.

3) When the soil is so compacted & water retentive that you must water in sips and cannot fully flush the soil at each watering for fear of creating conditions that will cause root rot. This isn't to say you MUST flush the soil at every watering, but the soil should drain well enough to ALLOW you to water this way whenever you prefer. This type of soil offers you the most protection against over-watering and you would really have to work hard at over-fertilizing in this type of soil. It will allow you to fertilize with a weak solution at every watering - even in winter if you prefer.

Incidentally, I reject the frequent anecdotal evidence that keeping N in soils at adequacy levels throughout the winter "forces" growth or "forces weak growth". Plants take what they need and leave the rest. While there could easily be the toxicity issues associated with too much fertilizer in soils due to a combination of inappropriate watering practices, inappropriate fertilizing practices, and an inappropriate soil, it's neither N toxicity NOR the presence of adequate N in soils that causes weak growth, it's low light levels.

Q. Is there any rule of thumb as to how often to remove and replace the old soil? Yes - every time you repot.

As always, I hope that those who read what I say about soils will ultimately take with them the idea that the soil is the foundation of every container planting & has effects that reach far beyond the obvious, but there is a snatch of lyrics from an old 70's song that might be appropriate: "... just take what you need and leave the rest ..." ;o)

NOTES:

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clipped on: 01.13.2014 at 10:39 pm    last updated on: 01.13.2014 at 10:40 pm

Container Soils and Your Plant's Nutrition

posted by: tapla on 11.02.2011 at 10:42 am in Plumeria Forum

A short while ago I was asked by a friend to comment on thread. I followed it for a while & found a few other threads on the forum that I thought afforded an opportunity for me to be helpful. Rather than spend time debating the merits of certain practices on other threads, I thought I would start a thread where anyone with an open mind can come to discuss all aspects of container culture, but particularly growing media and nutrition.

While some aspects of the plant sciences are open to interpretation and 'individual creativity', a considerable amount can be nailed down solidly. I often run into the phrase, "It works for me", used as though it is a debate ender, but how well something works is extremely subjective. For example, if someone is practicing methods that are quite limiting, then suddenly changes practices to something less limiting, the perception is all is well or, "This works great", never allowing that the new or even the preferred practice is still limiting and can be improved upon with a little better understanding of what's at work.

I've never read this approach to growing anywhere, so you may find my perspective unique: All plants are already pre programmed (genetically) to grow well and look beautiful. The only thing that keeps them from growing well is our inability to provide them with the cultural conditions needed to do so. In most cases, our habits are the factors most limiting to growth and vitality. This is particularly true in the areas of soil choice - nutritional supplementation - light. Light is pretty much a settled issue, but soils and nutrition are very confusing for many. You become a better grower by eliminating or reducing to the greatest degree possible, the limitations under which your plants are growing.

Good growing, like most things done well, does take a little knowledge and effort. If you're happy with the way things are going - there is no need to make the extra effort to read further in order that you might review another perspective; but if you're questioning whether or not there is something that might be done differently to help your plants grow better, this thread will, provide a place to come for suggestions for growing practices rooted in science instead of anecdote.

I understand that statement seems very bold, but all I would ask is that you reserve judgement until you've had the opportunity to hear a little of what I have to say. Having studied soil science, nutrition, and most of the intricacies associated with container culture for more than 20 years, and the (literally) thousands of positive responses I've garnered here at GW alone, has left me pretty confident that anyone wishing to sharpen their growing skills will be able to take at least some things from this thread. If not, there's little lost, it can just be ignored.

OK - that was the lead in. I'll start by saying that you can probably squeeze the most vitality and best growth from your plants if you first concentrate on getting the soil right. Your soil choice is where about 9/10 of your limits arise. You must be able to keep the roots happy if you have any hope of keeping the rest of the plant happy. To do that, focus on the soil's structure, not its ability to deliver nutrients. Nutrition is very simple, most people make it hard on themselves by trying to incorporate too much anecdotal misinformation, shooting themselves in the foot in the process.

Hopefully, this is all I need to do to pique the curiosity of enough readers to get the ball rolling. If not, I can say I tried. ;-) If you knew me, you'd know I'm not doing this for glory or acclaim, I'm doing it very simply because I love to help others. I've maintained a significant presence in the GW community and in my own community for more many years. I lecture widely on the suggested topic(s) I introduced, and look at helping people as a natural extension of my affinity for nurturing plants - sort of nurturing the people who nurture plants.

Thank you for your kind consideration. .... questions/comments?

Al

NOTES:

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clipped on: 01.13.2014 at 11:17 am    last updated on: 01.13.2014 at 11:17 am

Fertilizering Containerized Plants IV

posted by: tapla on 04.06.2012 at 04:30 pm in Container Gardening Forum

This topic has proven to be a fairly popular addition to the Container Gardening forum, having reached the maximum number of posts allowed on three previous occasions, so I'll post it for its fourth go-round. Nutrient supplementation has been discussed frequently, but usually in piecemeal fashion, on this forum and forums related. Prompted originally by a question about fertilizers in another thread, I decided to collect a few thoughts & present an overview that will hopefully be seen as a simplification and found to be helpful.

Fertilizing Containerized Plants IV

Let me begin with a brief and hopefully not too technical explanation of how plants absorb water from the soil and how they obtain the nutrients/solutes that are dissolved in that water. Most of us remember from our biology classes that cells have membranes that are semi-permeable. That is, they allow some things to pass through the walls, like water and select elements in ionic form dissolved in the water, while excluding other materials like large organic molecules. Osmosis is a natural phenomenon that is nature's attempt at creating a balance (isotonicity) in the concentration of solutes in water inside and outside of cells. Water and ionic solutes will pass in and out of cell walls until an equilibrium is reached and the level of solutes in the water surrounding the cell is the same as the level of solutes in the cell.

This process begins when the finest roots absorb water molecule by molecule at the cellular level from colloidal surfaces and water vapor in soil gasses, along with the nutrient load dissolved in that water, and distribute water and nutrients throughout the plant. I want to keep this simple, so I'll just say that the best water absorption occurs when the level of solutes in soil water is lowest, and in the presence of good amounts of oxygen (this is where I get to plug a well-aerated and free-draining soil). Deionized (distilled) water contains no solutes, and is easiest for plants to absorb. Of course, since distilled water contains no nutrients, using it alone practically guarantees deficiencies of multiple nutrients as the plant is shorted the building materials (nutrients) it needs to manufacture food, keep its systems orderly, and keep its metabolism running smoothly.

We already learned that if the dissolved solutes in soil water are low, the plant may be well-hydrated, but starving; however, if they are too high, the plant may have a large store of nutrients in the soil but because of osmotic interference the plant may be unable to absorb the water and could die of thirst in a sea of plenty. When this condition occurs, and is severe enough (high concentrations of solutes in soil water), it causes fertilizer burn (plasmolysis), a condition seen when plasma is torn from cell walls as the water inside the cell exits to maintain solute equilibrium with the water surrounding the cell.

Our job, because we cannot depend on an adequate supply of nutrients being supplied by the organic component of a container soil as it breaks down, is to provide a solution of dissolved nutrients in a concentration high enough that the supply remains in the adequate to luxury range, yet still low enough that it remains easy for the plant to take up enough water to be well-hydrated and free of drought stress. Electrical conductivity (EC) of, and the level of TDS (total dissolved solids) in the soil solution is a reliable way to judge the adequacy of solute concentrations and the plant's ability to take up water. There are meters that measure these concentrations, and for most plants the ideal range of conductivity is from 1.5 - 3.5 mS, with some, like tomatoes, being as high as 4.5 mS. This is more technical than I wanted to be, but I added it in case someone wanted to search 'mS' or 'TDS' or 'EC'. Most of us, including me, will have to be satisfied with simply guessing at concentrations, but understanding how plants take up water and fertilizer, as well as the effects of solute concentrations in soil water is an important piece of the fertilizing puzzle.

Now, some disconcerting news - you have listened to all this talk about nutrient concentrations, but what do we supply, when, and how do we supply them? We have to decide what nutrients are appropriate to add to our supplementation program, but how? Most of us are just hobby growers and cannot do tissue analysis to determine what is lacking. We CAN be observant tough, and learn the symptoms of various nutrient deficiencies - and we CAN make some surprising generalizations.

What if I said that the nutritional needs of all plants is basically the same and that one fertilizer could suit almost all the plants we grow in containers - that by increasing/decreasing the dosage as we water, we could even manipulate plants to bloom and fruit more abundantly? It's really quite logical, so please let me explain.

Tissue analysis of plants will nearly always show NPK %s to be very close to an average ratio of approximately 10:1.5:7. If we assign N the constant of 100, P and K will range from 13-19 and 45-70 respectively. (I'll try to remember to make a chart showing the relative ratios of all the other essential nutrients plants normally take from the soil at the end of what I write.) All we need to do is supply nutrients in approximately the same ratio as plants use them, and at concentrations sufficient to keep them in the adequate to luxury range at all times.

Remember that we can maximize water uptake by keeping the concentrations of solutes low, so a continual supply of a weak solution is best. Nutrients don't often just suddenly appear in large quantities in nature, so the low and continual dose method most closely mimics the nutritional supply Mother Nature offers. If you decide to adopt a "fertilize every time you water" approach, most liquid fertilizers can be applied at 3/4 to 1 tsp per gallon for best results. If you decide that is too much work, try halving the dose recommended & cutting the interval in half. You can work out the math for granular soluble fertilizers and apply at a similar rate.

The system is rather self regulating if fertilizer is applied in low concentrations each time you water, even with houseplants in winter. As the plant's growth slows, so does its need for both water and nutrients. Larger plants and plants that are growing robustly will need more water and nutrients, so linking nutrient supply to the water supply is a win/win situation all around.

Another advantage to supplying a continual low concentration of fertilizer is, it eliminates the tendency of plants to show symptoms of nutrient deficiencies after they have received high doses of fertilizer and then been allowed to return to a more favorable level of soil solute concentrations. Even at perfectly acceptable concentrations of nutrients in the soil, plants previously exposed to high concentrations of nutrients readily display deficiency symptoms, even at normal nutrient loads.

You will still need to guard against watering in sips, and that habit's accompanying tendency to ensure solute (salt) accumulation in soils. Remember that as salts accumulate, both water and nutrient uptake is made more difficult and finally impaired or made impossible in severe cases. Your soils should always allow you to water so that at least 10-15% of the total volume of water applied passes through the soil and out the drain hole to be discarded. This flushes the soil and carries accumulating solutes out the drain hole.

I use a liquid fertilizer with a full compliment of nutrients and micronutrients in a 3:1:2 ratio. Note that 'RATIO' is different than NPK %s. Also note how closely the 3:1:2 ratio fits the average ratio of NPK content in plant tissues, noted above (10:1.5:7). If the P looks a little high at 4, consider that in container soils, P begins to be more tightly held as pH goes from 6.5 to below 6.0, which is on the high side of most container soil's pH, so the manufacturer probably gave this some careful consideration. Also, P and K percentages shown on fertilizer packages are not the actual amount of P or K in the blend. The percentage of P on the package is the percentage of P2O5 (phosphorous pentoxide) and you need to multiply the percentage shown by .43 to get the actual amount of P in the fertilizer. Similarly, the K level percentage shown is actually the level of K2O ( potassium oxide) and must be multiplied by .83 to arrive at the actual amount of K supplied.

To answer the inevitable questions about specialty fertilizers and "special" plant nutritional requirements, let me repeat that plants need nutrients in roughly the same ratio. 'RATIO' is also an entirely a separate consideration from dosage. You'll need to adjust the dosage to fit the plant and perhaps strike a happy medium in containers that have a diversity of material.

If nutrient availability is unbalanced - if plants are getting more than they need of certain nutrients, but less than they need of others, the nutrient they need the most will be the one that limits growth. There are 6 factors that affect plant growth, vitality and yield; they are: air, water, light, temperature, soil or media and nutrients. Liebig's Law of Limiting Factors states the most deficient factor limits plant growth, and increasing the supply of non-limiting factors will not increase plant growth. Only by increasing most deficient nutrient will the plant growth increase. There is also an optimum combination/ratio of nutrients, and increasing them, individually or in various combinations can lead to toxicities and be as limiting as deficiencies.

When individual nutrients are available in excess, it not only unnecessarily contributes to the total volume of solutes in the soil solution, which makes it more difficult for the plant to absorb water and nutrients, it can also create an antagonistic deficiency of other nutrients as toxicity levels block a plant's ability to take them up. E.g., too much Fe (iron) can cause a Mn (manganese) deficiency, with the converse also true, Too much Ca (calcium) can cause a Mg (magnesium) deficiency. Too much P (phosphorous) can cause an insoluble precipitate with Fe and make Fe unavailable. It also interferes with the uptake of several other micro-nutrients. You can see why it is advantageous to supply nutrients in as close to the same ratio in which plants use them and at levels not so high that they interfere with water uptake. I know I'm repeating myself here, but this is an important point.

What about the high-P "Bloom Booster" fertilizers you might ask? To induce more prolific flowering, a reduced N supply will have more and better effect than the high P bloom formulas. When N is reduced, it slows vegetative growth without reducing photosynthesis. Since vegetative growth is limited by a lack of N, and the photosynthetic machinery continues to turn out food, it leaves an expendable surplus for the plant to spend on flowers and fruit. Plants use about 6 times more N than P, so fertilizers that supply more P than N are wasteful and more likely to inhibit blooms (remember that too much P inhibits uptake of Fe and many micro-nutrients - it raises pH unnecessarily as well, which could also be problematic). Popular "bloom-booster" fertilizers like 10-52-10 actually supply about 32x more P than your plant could ever use (in relationship to how much N it uses) and has the potential to wreak all kinds of havoc with your plants.

In a recent conversation with the CEO of Dyna-Gro, he confirmed my long held belief that circumstances would have to be very highly unusual for it to be ever beneficial to use a fertilizer in containers that supplies as much or more P than either N or K. This means that even commonly found 1:1:1 ratios like 20-20-20 or 14-14-14 supply more P than is necessary for best results.

The fact that different species of plants grow in different types of soil where they are naturally found, does not mean that one needs more of a certain nutrient than the other. It just means that the plants have developed strategies to adapt to certain conditions, like excesses and deficiencies of particular nutrients.

Plants that "love" acid soils, e.g., have simply developed strategies to cope with those soils. Their calcium needs are still the same as any other plant and no different from the nutrient requirements of plants that thrive in alkaline soils. The problem for acid-loving plants is that they are unable to adequately limit their calcium uptake, and will absorb too much of it when available, resulting in cellular pH-values that are too high. Some acid-loving plants also have difficulties absorbing Fe, Mn, Cu, or Zn, which is more tightly held in alkaline soils, another reason why they thrive in low pH (acid) soils.

So, If you select a fertilizer that is close in ratio to the concentration of major elements in plant tissues, you are going to be in good shape. Whether the fertilizer is furnished in chemical or organic form matters not a whit to the plant. Ions are ions, but there is one major consideration. Chemical fertilizers are available for immediate uptake while organic fertilizers must be acted on by passing through the gut of micro-organisms to break them down into usable elemental form. Since microorganism populations are affected by cultural conditions like moisture/air levels in the soil, soil pH, fertility levels, temperature, etc., they tend to follow a boom/bust cycle that has an impact on the reliability and timing of delivery of nutrients supplied in organic form, in container culture. Nutrients locked in hydrocarbon chains cannot be relied upon to be available when the plant needs them. This is a particular issue with the immobile nutrients that must be present in the nutrient stream at all times for the plant to grow normally.

What is my approach? I have been very happy with Foliage-Pro 9-3-6 liquid fertilizer. It has all the essential elements in a favorable ratio, and even includes Ca and Mg, which is unusual in soluble fertilizers. Miracle-Gro granular all-purpose fertilizer in 24-8-16 or liquid 12-4-8 are both close seconds and completely soluble, though they do lack Ca and Mg, which you can supply by incorporating lime or by including gypsum and Epsom salts in your fertilizer supplementation program. Ask if you need clarification on this point.

I often incorporate a granular micro-nutrient supplement in my soils when I make them (Micromax) or use a soluble micro-nutrient blend (STEM). I would encourage you to make sure your plants are getting all the micro-nutrients. More readily available than the supplements I use is Earth Juice's 'Microblast'.

When plants are growing robustly, I try to fertilize my plants weakly (pun intended) with a half recommended dose of the concentrate at half the suggested intervals. When plants are growing slowly, I still fertilize often, but with considerably reduced doses. It is important to realize your soil must drain freely and you must water so a fair amount of water drains from your container each time you water to fertilize this way. Last year, my display containers performed better than they ever have in years past & they were still all looking amazingly attractive at the beginning of Oct when I finally decided to dismantle them because of imminent cold weather. I attribute results primarily to a good soil and a healthy nutrient supplementation program.

What would I recommend to someone who asked what to use as an all-purpose fertilizer for nearly all their container plantings? If you can find it, a 3:1:2 ratio soluble liquid fertilizer (24-8-16, 12-4-8, 9-3-6 are all 3:1:2 ratio fertilizers) that contains all the minor elements would great.

How plants use nutrients - the chart I promised:

I gave Nitrogen, because it is the largest nutrient component, the value of 100. Other nutrients are listed as a weight percentage of N.
N 100
P 13-19 (16) 1/6
K 45-80 (62) 3/5
S 6-9 (8) 1/12
Mg 5-15 (10) 1/10
Ca 5-15 (10) 1/10
Fe 0.7
Mn 0.4
B(oron) 0.2
Zn 0.06
Cu 0.03
Cl 0.03
M(olybden) 0.003
To read the chart: P - plants use 13-19 parts of P or an average of about 16 parts for every 100 parts of N, or 6 times more N than P. Plants use about 45-80 parts of K or an average of about 62 parts for every 100 parts of N, or about 3/5 as much K as N, and so on.

If you're still with me - thanks for reading. It makes me feel like the effort was worth it. Let me know what you think - please.

Here is a link to the previous posting of A Fertilizer Program for Containerized Plants, in case you'd like to review some of the exchanges.

Another thread that has proven very helpful to a goodly number of forum participants can be found by following this link to information about How Water Behaves in Container Media. You'll find it a fairly detailed discussion about container soils.

Take care. Good luck and good growing!

Al

NOTES:

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clipped on: 01.11.2014 at 03:37 pm    last updated on: 01.11.2014 at 03:37 pm

Newbie Gardener! (Indoor Container)

posted by: Aysling on 01.09.2014 at 08:00 am in Container Gardening Forum

I've had a few strawberry plants before, but I've never put any time or research into gardening, and my results have been less than spectacular. I've never had the space for any kind of garden before, but with our current larger living space I decided to give indoor container gardening a try.

I'm starting with 20 plants (including the strawberries!), just under 40 square feet. I've read a few books and most suggest starting with under 50 square feet.

Unfortunately, I haven't been able to get answers to all of my questions, which is why I opened an account here!

1) If I'm growing indoors, I should be able to harvest any plant year round, as long as I can provide the correct temperature, sunlight and nutrients, correct?

2) I've been using SmartGardener to help plan my garden and it gives a temperature range for most plants, eg. carrots with a outdoor growing temp of 45- 75 F. Should I try to keep their temperature at 60 degrees? Are there any plants that need a range of temperatures in order to grow properly?

3) Final question: how can I provide separate temperatures within the same room? Would heating and cooling mats be sufficient? Since it's currently winter, could I place the cool temp plants closer to the window, partially close the vent, and put greenhouse-type covers on the warmer plants?

I'm trying to keep the overall garden as cost-effective as possible, especially this first season, and I'm not afraid of a little DIY to make that happen! I'm already planning on making my own planters and light fixtures.

NOTES:

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clipped on: 01.11.2014 at 03:37 pm    last updated on: 01.11.2014 at 03:37 pm

Container Soils - Water Movement and Retention XVII

posted by: tapla on 06.10.2013 at 04:52 pm in Container Gardening Forum

Container Soils - Water Movement and Retention XVII

I first posted this thread back in March of '05. Sixteen times it has reached the maximum number of posts GW allows to a single thread, which is much more attention than I ever imagined it would garner. I have reposted it in no small part because it has been great fun, and a wonderful catalyst in the forging of new friendships and in increasing my list of acquaintances with similar growing interests. The forum and email exchanges that stem so often from the subject are in themselves enough to make me hope the subject continues to pique interest, and the exchanges provide helpful information. Most of the motivation for posting this thread another time comes from the reinforcement of hundreds of participants over the years that strongly suggests the information provided in good-spirited collective exchange has made a significant difference in the quality of their growing experience. I'll provide links to some of the more recent of the previous dozen threads and nearly 2,500 posts at the end of what I have written - just in case you have interest in reviewing them. Thank you for taking the time to examine this topic - I hope that any/all who read it take at least something interesting and helpful from it. I know it's long. My hope is that you find it worth the read, and the time you invest results in a significantly improved growing experience.

Since there are many questions about soils appropriate for use in containers, I'll post basic mix recipes later, in case any would like to try the soil. It will follow the information.

Before we get started, I'd like to mention that I wrote a reply and posted it to a thread recently, and I think it is well worth considering. It not only sets a minimum standard for what constitutes a 'GOOD' soil, but also points to the fact that not all growers look at container soils from the same perspective, which is why growers so often disagree on what makes a 'good' soil. I hope you find it thought provoking:

Is Soil X a 'Good' Soil?

I think any discussion on this topic must largely center around the word "GOOD", and we can broaden the term 'good' so it also includes 'quality' or 'suitable', as in "Is soil X a quality or suitable soil?"

How do we determine if soil A or soil B is a good soil? and before we do that, we'd better decide if we are going to look at it from the plant's perspective or from the grower's perspective, because often there is a considerable amount of conflict to be found in the overlap - so much so that one can often be mutually exclusive of the other.

We can imagine that grower A might not be happy or satisfied unless knows he is squeezing every bit of potential from his plants, and grower Z might not be happy or content unless he can water his plants before leaving on a 2-week jaunt, and still have a weeks worth of not having to water when he returns. Everyone else is somewhere between A and Z; with B, D, F, H, J, L, N, P, R, T, V, X, and Y either unaware of how much difference soil choice can make, or they understand but don't care.

I said all that to illustrate the large measure of futility in trying to establish any sort of standard as to what makes a good soil from the individual grower's perspective; but let's change our focus from the pointless to the possible.

We're only interested in the comparative degrees of 'good' and 'better' here. It would be presumptive to label any soil "best". 'Best I've found' or 'best I've used' CAN sometimes be useful for comparative purposes, but that's a very subjective judgment. Let's tackle 'good', then move on to 'better', and finally see what we can do about qualifying these descriptors so they can apply to all growers.

I would like to think that everyone would prefer to use a soil that can be described as 'good' from the plant's perspective. How do we determine what a plant wants? Surprisingly, we can use %s established by truly scientific studies that are widely accepted in the greenhouse and nursery trades to determine if a soil is good or not good - from the plant's perspective, that is. Rather than use confusing numbers that mean nothing to the hobby grower, I can suggest that our standard for a good soil should be, at a minimum, that you can water that soil properly. That means, that at any time during the growth cycle, you can water your plantings to beyond the point of saturation (so excess water is draining from the pot) without the fear of root rot or compromised root function or metabolism due to (take your pick) too much water or too little air in the root zone.

I think it's very reasonable to withhold the comparative basic descriptor, 'GOOD', from soils that can't be watered properly without compromising root function, or worse, suffering one of the fungaluglies that cause root rot. I also think anyone wishing to make the case from the plant's perspective that a soil that can't be watered to beyond saturation w/o compromising root health can be called 'good', is fighting on the UP side logic hill.

So I contend that 'good' soils are soils we can water correctly; that is, we can flush the soil when we water without concern for compromising root health/function/metabolism. If you ask yourself, "Can I water correctly if I use this soil?" and the answer is 'NO' ... it's not a good soil ... for the reasons stated above.

Can you water correctly using most of the bagged soils readily available? 'NO', I don't think I need to point to a conclusion.

What about 'BETTER'? Can we determine what might make a better soil? Yes, we can. If we start with a soil that meets the minimum standard of 'good', and improve either the physical and/or chemical properties of that soil, or make it last longer, then we have 'better'. Even if we cannot agree on how low we wish to set the bar for what constitutes 'good', we should be able to agree that any soil that reduces excess water retention, increases aeration, ensures increased potential for optimal root health, and lasts longer than soils that only meet some one's individual and arbitrary standard of 'good', is a 'better' soil.

All the plants we grow, unless grown from seed, have the genetic potential to be beautiful specimens. It's easy to say, and easy to see the absolute truth in the idea that if you give a plant everything it wants it will flourish and grow; after all, plants are programmed to grow just that way. Our growing skills are defined by our ability to give plants what they want. The better we are at it, the better our plants will grow. But we all know it's not that easy. Lifetimes are spent in careful study, trying to determine just exactly what it is that plants want and need to make them grow best.

Since this is a soil discussion, let's see what the plant wants from its soil. The plant wants a soil in which we have endeavored to provide in available form, all the essential nutrients, in the ratio in at which the plant uses them, and at a concentration high enough to prevent deficiencies yet low enough to make it easy to take up water (and the nutrients dissolved in the water). First and foremost, though, the plant wants a container soil that is evenly damp, never wet or soggy. Giving a plant what it wants, to flourish and grow, doesn't include a soil that is half saturated for a week before aeration returns to the entire soil mass, even if you only water in small sips. Plants might do 'ok' in some soils, but to actually flourish, like they are genetically programmed to do, they would need to be unencumbered by wet, soggy soils.

We become better growers by improving our ability to reduce the effects of limiting factors, or by eliminating those limiting factors entirely; in other words, by clearing out those influences that stand in the way of the plant reaching its genetic potential. Even if we are able to make every other factor that influences plant growth/vitality absolutely perfect, it could not make up for a substandard soil. For a plant to grow to its genetic potential, every factor has to be perfect, including the soil. Of course, we'll never manage to get to that point, but the good news is that as we get closer and closer, our plants get better and better; and hopefully, we'll get more from our growing experience.

In my travels, I've discovered it almost always ends up being that one little factor that we willingly or unwittingly overlooked that limits us in our abilities, and our plants in their potential.

Food for thought:
A 2-bit plant in a $10 soil has a future full of potential, where a $10 plant in a 2-bit soil has only a future filled with limitations. ~ Al

Container Soils - Water Movement & Retention,

As container gardeners, our first priority should be to ensure the soils we use are adequately aerated for the life of the planting, or in the case of perennial material (trees, shrubs, garden perennials), from repot to repot. Soil aeration/drainage is the most important consideration in any container planting. Soils are the foundation that all container plantings are built on, and aeration is the very cornerstone of that foundation. Since aeration and drainage are inversely linked to soil particle size, it makes good sense to try to find and use soils or primary components with particles larger than peat/compost/coir. Durability and stability of soil components so they contribute to the retention of soil structure for extended periods is also extremely important. Pine and some other types of conifer bark fit the bill nicely, but I'll talk more about various components later.

What I will write also hits pretty hard against the futility in using a drainage layer of coarse materials in attempt to improve drainage. It just doesn't work. All it does is reduce the total volume of soil available for root colonization. A wick can be employed to remove water from the saturated layer of soil at the container bottom, but a drainage layer is not effective. A wick can be made to work in reverse of the self-watering pots widely being discussed on this forum now.

Consider this if you will:

Container soils are all about structure, and particle size plays the primary role in determining whether a soil is suited or unsuited to the application. Soil fills only a few needs in container culture. Among them are: Anchorage - a place for roots to extend, securing the plant and preventing it from toppling. Nutrient Retention - it must retain a nutrient supply in available form sufficient to sustain plant systems. Gas Exchange - it must be amply porous to allow air to move through the root system and gasses that are the by-product of decomposition to escape. Water - it must retain water enough in liquid and/or vapor form to sustain plants between waterings. Air - it must contain a volume of air sufficient to ensure that root function/metabolism/growth is not impaired. This is extremely important and the primary reason that heavy, water-retentive soils are so limiting in their affect. Most plants can be grown without soil as long as we can provide air, nutrients, and water, (witness hydroponics). Here, I will concentrate primarily on the movement and retention of water in container soil(s).

There are two forces that cause water to move through soil - one is gravity, the other capillary action. Gravity needs little explanation, but for this writing I would like to note: Gravitational flow potential (GFP) is greater for water at the top of the container than it is for water at the bottom. I'll return to that later.

Capillarity is a function of the natural forces of adhesion and cohesion. Adhesion is water's tendency to stick to solid objects like soil particles and the sides of the pot. Cohesion is the tendency for water to stick to itself. Cohesion is why we often find water in droplet form - because cohesion is at times stronger than adhesion; in other words, water's bond to itself can be stronger than the bond to the object it might be in contact with; cohesion is what makes water form drops. Capillary action is in evidence when we dip a paper towel in water. The water will soak into the towel and rise several inches above the surface of the water. It will not drain back into the source, and it will stop rising when the GFP equals the capillary attraction of the fibers in the paper.

There will be a naturally occurring "perched water table" (PWT) in containers when soil particulate size is under about .100 (just under 1/8) inch. Perched water is water that occupies a layer of soil at the bottom of containers or above coarse drainage layers that tends to remain saturated & will not drain from the portion of the pot it occupies. It can evaporate or be used by the plant, but physical forces will not allow it to drain. It is there because the capillary pull of the soil at some point will surpass the GFP; therefore, the water does not drain, it is said to be 'perched'. The smaller the size of the particles in a soil, the greater the height of the PWT. Perched water can be tightly held in heavy (comprised of small particles) soils where it perches (think of a bird on a perch) just above the container bottom where it will not drain; or, it can perch in a layer of heavy soil on top of a coarse drainage layer, where it will not drain.

Imagine that we have five cylinders of varying heights, shapes, and diameters, each with drain holes. If we fill them all with the same soil mix, then saturate the soil, the PWT will be exactly the same height in each container. This saturated area of the container is where roots initially seldom penetrate & where root problems frequently begin due to a lack of aeration and the production of noxious gasses. Water and nutrient uptake are also compromised by lack of air in the root zone. Keeping in mind the fact that the PWT height is dependent on soil particle size and has nothing to do with height or shape of the container, we can draw the conclusion that: If using a soil that supports perched water, tall growing containers will always have a higher percentage of unsaturated soil than squat containers when using the same soil mix. The reason: The level of the PWT will be the same in each container, with the taller container providing more usable, air holding soil above the PWT. From this, we could make a good case that taller containers are easier to grow in.

A given volume of large soil particles has less overall surface area when compared to the same volume of small particles and therefore less overall adhesive attraction to water. So, in soils with large particles, GFP more readily overcomes capillary attraction. They simply drain better and hold more air. We all know this, but the reason, often unclear, is that the height of the PWT is lower in coarse soils than in fine soils. The key to good drainage is size and uniformity of soil particles. Mixing large particles with small is often very ineffective because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential. An illustrative question: How much perlite do we need to add to pudding to make it drain well?

I already stated I hold as true that the grower's soil choice when establishing a planting for the long term is the most important decision he/she will make. There is no question that the roots are the heart of the plant, and plant vitality is inextricably linked in a hard lock-up with root vitality. In order to get the best from your plants, you absolutely must have happy roots.

If you start with a water-retentive medium, you cannot effectively amend it to improve aeration or drainage characteristics by adding larger particulates. Sand, perlite, Turface, calcined DE ...... none of them will work effectively. To visualize why sand and perlite can't change drainage/aeration, think of how well a pot full of BBs would drain (perlite); then think of how poorly a pot full of pudding would drain (bagged soil). Even mixing the pudding and perlite/BBs together 1:1 in a third pot yields a mix that retains the drainage characteristics and PWT height of the pudding. It's only after the perlite become the largest fraction of the mix (60-75%) that drainage & PWT height begins to improve. At that point, you're growing in perlite amended with a little potting soil.

You cannot add coarse material to fine material and improve drainage or the ht of the PWT. Use the same example as above & replace the pudding with play sand or peat moss or a peat-based potting soil - same results. The benefit in adding perlite to heavy soils doesn't come from the fact that they drain better. The fine peat or pudding particles simply 'fill in' around the perlite, so drainage & the ht of the PWT remains the same. All perlite does in heavy soils is occupy space that would otherwise be full of water. Perlite simply reduces the amount of water a soil is capable of holding because it is not internally porous. IOW - all it does is take up space. That can be a considerable benefit, but it makes more sense to approach the problem from an angle that also allows us to increase the aeration AND durability of the soil. That is where Pine bark comes in, and I will get to that soon.

If you want to profit from a soil that offers superior drainage and aeration, you need to start with an ingredient as the basis for your soils that already HAVE those properties, by ensuring that the soil is primarily comprised of particles much larger than those in peat/compost/coir/sand/topsoil, which is why the recipes I suggest as starting points all direct readers to START with the foremost fraction of the soil being large particles, to ensure excellent aeration. From there, if you choose, you can add an appropriate volume of finer particles to increase water retention. You do not have that option with a soil that is already extremely water-retentive right out of the bag.

I fully understand that many are happy with the results they get when using commercially prepared soils, and I'm not trying to get anyone to change anything. My intent is to make sure that those who are having trouble with issues related to soil, understand why the issues occur, that there are options, and what they are.

We have seen that adding a coarse drainage layer at the container bottom does not improve drainage. It does though, reduce the volume of soil required to fill a container, making the container lighter. When we employ a drainage layer in an attempt to improve drainage, what we are actually doing is moving the level of the PWT higher in the pot. This simply reduces the volume of soil available for roots to colonize. Containers with uniform soil particle size from top of container to bottom will yield better and more uniform drainage and have a lower PWT than containers using the same soil with added drainage layers.

The coarser the drainage layer, the more detrimental to drainage it is because water is more (for lack of a better scientific word) reluctant to make the downward transition because the capillary pull of the soil above the drainage layer is stronger than the GFP. The reason for this is there is far more surface area on soil particles for water to be attracted to in the soil above the drainage layer than there is in the drainage layer, so the water perches. I know this goes against what most have thought to be true, but the principle is scientifically sound, and experiments have shown it as so. Many nurserymen employ the pot-in-pot or the pot-in-trench method of growing to capitalize on the science.

If you discover you need to increase drainage, you can simply insert an absorbent wick into a drainage hole & allow it to extend from the saturated soil in the container to a few inches below the bottom of the pot, or allow it to contact soil below the container where the earth acts as a giant wick and will absorb all or most of the perched water in the container, in most cases. Eliminating the PWT has much the same effect as providing your plants much more soil to grow in, as well as allowing more, much needed air in the root zone.

In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they suffer/die because there is insufficient air at the root zone to insure normal root function, so water/nutrient uptake and root metabolism become seriously impaired.

To confirm the existence of the PWT and how effective a wick is at removing it, try this experiment: Fill a soft drink cup nearly full of garden soil. Add enough water to fill to the top, being sure all soil is saturated. Punch a drain hole in the bottom of the cup and allow the water to drain. When drainage has stopped, insert a wick into the drain hole . Take note of how much additional water drains. Even touching the soil with a toothpick through the drain hole will cause substantial additional water to drain. The water that drains is water that occupied the PWT. A greatly simplified explanation of what occurs is: The wick or toothpick "fools" the water into thinking the pot is deeper than it is, so water begins to move downward seeking the "new" bottom of the pot, pulling the rest of the water in the PWT along with it. If there is interest, there are other simple and interesting experiments you can perform to confirm the existence of a PWT in container soils. I can expand later in the thread.

I always remain cognizant of these physical principles whenever I build a soil. I have not used a commercially prepared soil in many years, preferring to build a soil or amend one of my 2 basic mixes to suit individual plantings. I keep many ingredients at the ready for building soils, but the basic building process usually starts with conifer bark and perlite. Sphagnum peat plays a secondary role in my container soils because it breaks down too quickly to suit me, and when it does, it impedes drainage and reduces aeration. Size matters. Partially composted conifer bark fines (pine is easiest to find and least expensive) works best in the following recipes, followed by uncomposted bark in the <3/8" range.

Bark fines of pine, fir or hemlock, are excellent as the primary component of your soils. The lignin contained in bark keeps it rigid and the rigidity provides air-holding pockets in the root zone far longer than peat or compost mixes that too quickly break down to a soup-like consistency. Conifer bark also contains suberin, a lipid sometimes referred to as nature's preservative. Suberin, more scarce as a presence in sapwood products and hardwood bark, dramatically slows the decomposition of conifer bark-based soils. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains - it retains its structure.

Note that there is no sand or compost in the soils I use. Sand, as most of you think of it, can improve drainage in some cases, but it reduces aeration by filling valuable macro-pores in soils. Unless sand particle size is fairly uniform and/or larger than about BB size, I leave it out of soils. Compost is too fine and unstable for me to consider using in soils in any significant volume as well. The small amount of micro-nutrients it supplies can easily be delivered by one or more of a number of chemical or organic sources that do not detract from drainage/aeration.

The basic soils I use ....

The 5:1:1 mix:

5 parts pine bark fines, dust - 3/8 (size is important
1 part sphagnum peat (not reed or sedge peat please)
1-2 parts perlite (coarse, if you can get it)
garden lime (or gypsum in some cases)
controlled release fertilizer (if preferred)

Big batch:
2-3 cu ft pine bark fines
5 gallons peat
5 gallons perlite
2 cups dolomitic (garden) lime (or gypsum in some cases)
2 cups CRF (if preferred)

Small batch:
3 gallons pine bark
1/2 gallon peat
1/2 gallon perlite
4 tbsp lime (or gypsum in some cases)
1/4 cup CRF (if preferred)

I have seen advice that some highly organic (practically speaking - almost all container soils are highly organic) container soils are productive for up to 5 years or more. I disagree and will explain why if there is interest. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will long outlast any peat based soil) you should only expect a maximum of two to three years life before a repot is in order. Usually perennials, including trees (they're perennials too) should be repotted more frequently to insure they can grow at as close to their genetic potential within the limits of other cultural factors as possible. If a soil is desired that will retain structure for long periods, we need to look more to inorganic components. Some examples are crushed granite, fine stone, VERY coarse sand (see above - usually no smaller than BB size in containers, please), Haydite, lava rock (pumice), Turface, calcined DE, and others.

For long term (especially woody) plantings and houseplants, I use a superb soil that is extremely durable and structurally sound. The basic mix is equal parts of screened pine bark, Turface, and crushed granite.

The gritty mix:

1 part uncomposted screened pine or fir bark (1/8-1/4")
1 part screened Turface
1 part crushed Gran-I-Grit (grower size) or #2 cherrystone
1 Tbsp gypsum per gallon of soil (eliminate if your fertilizer has Ca)
CRF (if desired)

I use 1/8 -1/4 tsp Epsom salts (MgSO4) per gallon of fertilizer solution when I fertilize if the fertilizer does not contain Mg (check your fertilizer - if it is soluble, it is probable it does not contain Ca or Mg. If I am using my currently favored fertilizer (I use it on everything), Dyna-Gro's Foliage-Pro in the 9-3-6 formulation, and I don't use gypsum or Epsom salts in the fertilizer solution.

If there is interest, you'll find some of the more recent continuations of the thread at the links below:

Post XVI
Post XV
Post XIV
Post XIII
Post XII

If you feel you were benefited by having read this offering, you might also find this thread about Fertilizing Containerized Plants helpful.

If you do find yourself using soils you feel are too water-retentive, you'll find some Help Dealing with Water Retentive Soils by following this embedded link.

If you happen to be at all curious about How Plant Growth is Limited, just click the embedded link.

Finally, if you are primarily into houseplants, you can find an Overview of the Basics that should provide help in avoiding the most common pitfalls.

As always - best luck. Good growing!! Let me know if you think there is anything I might be able to help you with.

Al

This post was edited by tapla on Mon, Jun 10, 13 at 17:06

NOTES:

5-1-1 potting mix recipe
clipped on: 01.10.2014 at 01:43 pm    last updated on: 01.10.2014 at 01:48 pm