More soiless growing medium questions

I'm in the initial stages of creating some raised beds and I have decided to use some of the soiless growing medium techniques discussed here. I decided to take this approach for the promise of healthier plants of course but also for reduced soil maintenance. I have a few questions -

1. Someone stated that the raised bed mix they suggested retains much more water than the container mix. It appears that these mixes are very similar except for the addition of pearlite and possibly greater amounts of turface/granite in the container mix. Is it primarily the amount of turface and/or granite that controls the water retention? I have an extensive drip system installed but I still don't want to water my raised beds more than I have to. For the record the suggested ratios are 5 parts pine bark, 1 or 2 parts sphagnum peat, 1 part turface and 1 part grower's grit. I believe the container mix ratios were similar but included pearlite and possibly greater ratios of turface and/or granite.

2. West of the rockies the 2 major mulch bark suppliers call their fine bark product "Western Bark" as opposed to "Pine Bark" east of the rockies and the websites don't say exactly what tree species are used. They sell fine cedar bark separately. I assume it's not overly critical as to the species of bark? Also, I thought that uncomposted bark is a nitrogen sink. Is it necessary to supplement with nitrogen? If so, is it adviseable to use a soil testing kit or simply following suggested application rates?

3. Is it also advisable to monitor PH levels for either the raised beds or containers? I saw that the use dolomite lime is recommended for containers - is this to compensate for the acidity of peat moss? I have one of those low cost electronic PH monitors. Are those accurate or is a chemical test preferable? How would you know how much lime to add?Conventional wisdom says that compost is a PH buffer and since that is no longer present it seems that the PH could more easily go outside optimum ranges.

I know some would say that I'm making this more complicated than necessary and it's probably true but since I'm planning on preparing about 300 sq ft of beds I'd like to avoid any obvious mistakes.

Thanks

aaaaah San Jose , my my , I am from Palo Alto,
I m not good at composting, as Kenton will tell you (heehee) :) or Soferdig, i can't even get my tumbler to work, hahaha. but i just pile it in a bin and let it go with mother nature. Try Llama poop.
But i did a ph test on my soil and i posted it in another thread soil and compost part two,
If you are interested in what one looks like and may give you an idea. Kenton helped me with figuring out the numbers. just a thought.
sue

Do a forum search and you should find plenty of thread discussions about the soilless mixes.
Use D-Mail to send your questions to "tapla". He is very knowledgeable about the mixes and should be able to answer your questions based on knowledge and experience.

Yardenman - No wonder these questions appeared in my mail. ;o) I don't save the messages I sent, so perhaps Alex would be kind enough to copy/paste my reply to the forum to save me the repeat effort? If I remember, it was sort of lengthy, as is the norm for me. ;o)

I do really thank you guys for the vote of confidence. It helps to think there's a possibility what I write might be helping.

Al

Sorry tapala for jumping the gun and reposting question here. Wasn't sure if you were still listening.

Also, I appreciate the people giving me composting advice but it's not really practical for me given the small size of my yard and the nuisance factor for me, my wife and possibly the neighbors. I have purchased massive quantities of compost in the past but the problem is you never know exactly what you are getting and it's even obvious that it varies considerably from batch to batch. That is why I immediately recognized the advantage of Tapalas method for my situation.

Here is the D-mail thread -

Tapala,

I read your posts on potting/raised bed soils with great interest. I didn't want to add to the thread because it looked like it degenerated into useless banter.

Anyhow, I recently constructed a raised bed that I plan to use for various ornamental plants. It is 12" deep and about 300 sq ft. To fill it I first had 6 yards of "planters mix" delivered which seems to contain a mix of soil, compost and manure. It's fairly light but it does turn muddy when wet. I ammended this heavily with composted bark from the home center and some bulk potting soil. Since I have invested much time effort and money into this I would like to make the soil as fertile as possible. I still have some room available for ammendments. I have located a source for turface.

Would you recommend I add turface and peat to the bed?

I also can't help but ask - I assume you have to fertilize your plants regularly (potted or raised bed) since you have little or no organic material in the soil. I'm not clear if you use synthetic fertilizers but if you do doesn't conventional wisdom tell us that this will cause salt buildup? Perhaps with the potted plants this is not a real problem since your substrate does not hold the salts or flushing them is nothing more than a heavy watering.

My original strategy for the raised beds was to use little or no synthetic fertilzer since the beds have to remain undisturbed long term and cannot easily be flushed. May I ask what your fertilization strategy is for containers as well as raised beds?

Thanks,

Alex


tapla
Bay City, MI
May 5, 2006
4:28 PM
Would you recommend I add turface and peat to the bed?

I think I would add Turface if you don't mind the expense. An alternative would be pumice or lava stone, haydite, or another calcined clay product. I don't see the peat being of any benefit at this point of the soil is soggy. You could also increase the pine or fir bark content to increase drainage temporarily. You're going to need a mineral component eventually, though. You could also use coarse sand or rotted granite in a raised bed with very good results.

I only fertilized the first year. My raised bed soil is about:
5 parts pine bark
1 or 2 parts sphagnum
1 part Turface
1 part sand

I haven't had to compensate for shrinkage yet, but when I do, I'll use pine bark only. You can see the great tilth & the richness of the soil in the pic. It is full of worms * other soil organisms.

Remember, raised beds follow the rules or physics of garden culture. Container physics are totally different & the cultures mix poorly. The soil in the pic is a fantastic soil in the raised beds, but would hold far too much water for container use.

In container culture, if you build your soil properly, You can saturate it at each watering, The surplus carries fertilizer salts out the drain hole. I never worry about plasmolysis (salt build up or fertilizer burn) with my container soils. There is no need to worry about build-up in beds as rain carries it away, much the same as over-watering containers does.

Digest this & get back to me about fertilizer strategies if your question regards containers. If it's about beds, You'll need to use a high N fertilizer for the first year only. After that, a balanced blend, if needed at all, will be good.

Al

Click the image for an enlarged view.

alexh
San Jose, CA
May 17, 2006
5:33 PM
Thanks Tapala,

I'm about to implement the soil mix so I justed wanted to ask a couple more questions to avoid any mistakes-

1. You said that your raised bed mix retains much more water than your container mix. It appears that these mixes are very similar except for the addition of pearlite and possibly greater amounts of turface/granite in your container mix. Is it primarily a greater amount of turface and/or granite that controls the water retention? I have an extensive drip system installed but I still don't want to water my raised beds more than I have to.

2. West of the rockies the 2 major mulch bark suppliers call their fine bark product western bark and the websites don't say exactly what species are used. They sell fine cedar bark seperately. I assume it's not overly critical as to the species of bark? Also, I thought that uncomposted bark is a nitrogen sink. Is this why you supplement with nitrogen the first year? Do you use soil testing kits or just use suggested application rates?

3. Do you find that you have to monitor PH levels for either your raised beds or containers? I saw that you use dolomite lime in your containers - is this to compensate for the acidity of peat moss?

4. I will have some organic material and thus micro-nutrients in my raised beds just because of residuals left over from the initial prep. Do you think I should use Micro-max? I believe you said you have a supplier for this. Based on my sq footage I would need at most 5 lbs per application according to the tech sheet. They did not say how many applications per year.

Thanks,

Alex
tapla
Bay City, MI
May 19, 2006
8:00 AM
1) It is the wicking effect of the earth below the beds that allows you to grow in a far denser and more water retentive soil. The capillary pull of the soil below plus gravity 'pulls' the water from the raised bed.

2) I use primarily yellow pine and fir bark. I have used hemlock with good results. Not having grown in a product called cedar bark, I cannot comment & be fair to you. If it is substantially heartwood & little bark, do avoid it. Yes, the added N is to compensate for tie-up. You'll not need it in second year. I am pretty experienced & am able to use leaf color as a guide for N needs. When oldest leaves lighten, I apply a fertilizer with a high first #. I usually use what was Miracid - I think it is azalea food now. I don't test raised bed or container soils. They are so high in organic matter that pH is pretty unimportant as it relates to nutrient lock-up. Organic soils hold ions very loosely and readily available for plant uptake.

3) No - I never monitor for reason above. I've never found it important and an exercise in futility as container pH fluctuates widely over the course of a season and the life of a planting. Incidentally, recent studies have shown the container pH as low as 4.0 still produces excellent growth in containers. I use dolomitic lime for the Ca & Mg, not pH buffering.

4) I did not use it in my fertilizer program, but I did incorporate a controlled release fertilizer that contained the minor elements. I suspect that applications of seaweed/fish emulsions should help (be entirely adequate) in that dept., or you could choose a fertilizer that contains the minors.

Al






This message was edited May 19, 2006 12:03 PM

>I'm in the initial stages of creating some raised beds and I have decided to use some of the soiless growing medium techniques discussed here. I decided to take this approach for the promise of healthier plants of course but also for reduced soil maintenance.

I have to ask: who is promising healthier plants? Is there something so seriously wrong with your soil that you wish to invest so much time, labor and money into providing a replacement for soil that is already there?

I built 1600 square feet of raised beds last season and more this year. Beyond the fact that I would have gone broke buying or making the potting soil to cover all that, it seems like an incredible waste of resources, including the garden's most valuable (and only permanent) asset, the soil.

In my experience, there is no substitue for building healthy soil. All time, energy and organic matter spent in improving the native soil is a lasting investment and not a short-term fix which is quickly depleted.

Just my opinion.

Wayne

>Is there something so seriously wrong with your soil that you wish to invest so much time, labor and money into providing a replacement for soil that is already there?

Your probably very lucky to have a decent soil base where you live. I live in the San Jose foothills which are similar to foothills from Santa Barbara to Sacramento. You have probably seen pictures of these hills in magazines - large beautiful oaks surrounded by bright green native grasses. What those pictures don't show is that those conditions only last a few weeks at best and often just 1 or 2 weeks. Granted this is largely due to lack of moisture but the fact is nothing substantial has grown in these hills for thousands of years and thus there is typically less than 1" of topsoil. I did a drainage test last fall and the drainage rate was literally ZERO. If the evap rate is low the water will stay there forever. It's not impossible to condition this soil - I have done it by adding about 50% compost by volume. Problem is you now have a hole or trench and if you accidentally overwater, or there is an unusual amount of rain all depressions will fill with water. When I dig around in my yard, any native soil left on concrete or tools dries to almost, and I'm not exaggerating, a cement like consistency. It has to be chipped off, it cannot be washed off.

I talked to people in my area that plant ornamentals like Camelias, Azeleas Peonies etc and the experienced people all told me that the plants will never be vigorous if there not in a raised bed. My raised bed is small, about 300 sq ft.

Also I'm not really clear on what you filled your raised bed with. You say I should use the existing soil but a raised bed by definition starts out empty. On my 7000 sq ft lot, of which probably 3000 is covered by house or concrete, I can't very well find any "extra" dirt lying around. Topsoil around here is $30/yd plus $50 for delivery and they don't know what it is! From what I can tell it's not much better than what's already there.

I don't "fill" the beds since there is nothing to fill. Filling is only required when one finds it necessary to build a frame to contain the soil. My beds are mounded and do not have sides.

I build the beds by double digging them in the manner of the French Intensive gardeners and the bio-intensive method. The soil is loosened to about 24" deep. The existing soil layers are maintained in the double-digging system and compost and other organic matter and nutrients are worked into the top 6" of soil. As you can see, the focus is on building the soil, not replacing it.

Permanent pathways are created around the beds with the path's topsoil pulled onto the beds where it will feed plants rather than get walked on. The lossening of the soil gives it a degree of "fluff" and, along with the addition of lots of organic matter and the additional soil from the paths, combine to form the raised bed from previously level ground.

My soil was mostly a very sandy, fast draining soil, but by incorporating large amounts of compost and other organic matter into the top layer, it has quickly begun turning into a productive soil, well drained yet able to absorb and retain adequate moisture and nutrients.

Wayne

ADKG - A promise needn't be a pledge or vow. It can simply be a good indication that something will occur. A clear dawn holds promise of a sunny day like a soil built with other than rocks and scree can holds promise of healthier, more vital plants. It's probably not a case of someone giving any sort of assurances that Alex will be instantly successful, just the words he chose to express himself.

Maybe it's just me, but I would rather applaud his research and efforts than be too critical of his decisions. Given what he has to work with and his cultural conditions, I'd guess that your methods/ideas (so far) would border on unworkable in his situation.

Below, is a picture of the soil that I suggested he build in his beds. The primary ingredient is conifer bark, and I bet it can be had for about $1 a cu ft. The most expensive ingredient is the Turface, but he might have something local that would work as well. As an obvious connoisseur of fine soils, you should recognize the excellent tilth and richness of the 5 year old soil in the picture. It is wonderfully alive and productive, and Alex should expect the promise of a similar soil should he decide to build it.

I was fortunate enough to buy my home from a man that owned a large, upscale greenhouse/nursery operation. My soils were close to perfect when I arrived & I've spent 30 years here further building them. You might be interested to learn that I chose to make my own soils in my 600+ sq ft of raised beds, using native soil only as as something to build the beds on. While some might envy your soils, there are certain applications where they simply do not fit needs. E.g, I grow on lots of pines & junipers for bonsai, and I certainly do not want a rich and moisture retentive soil for those plants. Other examples might include rock or alpine gardens. We just have to allow that my/your methods are not for all, nor can they be applied to every situation across the board.

Alex, you're doing fine, hang in there. I can't speak for anyone else, but I'm pulling for you. ;o)

It's a very interesting coincidence that you say the biointensive techniques I use would "border on unworkable" in Alex's area. I've read the book "How to Grow More Vegetables" by John Jeavons, who began using the biointensive teachings of Alan Chadwick in 1972 by creating incredibly productive gardens on marginal land in Palo Alto, which I believe is just a few miles from San Jose and presumably has similar or identical soils. The Ecology Action gardens, formerly located on Syntex Corporation land are no longer being worked since they moved to a larger site a bit north in WIllits, CA, but there is a lot of documentation about the research and successes that resulted from the work in the original Palo Alto center.

My comments aren't about criticizing Alex's decisions. It is about offering alternatives to spending time and money that may prove to be unnecessary and more importantly to me, gardening and building our soil in a sustainable manner. Alex is free to accept or reject the information or my opinions in the spirit it is given.

Wayne

AlexH --- if you already have not purchased the pricey and hard-to-find Turface, a less expensive and more readily available alternative is a spill absorbing product sold at car parts supply stores. It is a clay product used to soak up oil/fluid spills in a garage, but it also can be used in place of Turface. In fact the bag I bought at a local Auto Zone store (Driz-It all purpose premium floor absorbent by Waverly Minerals, Inc) lists the gardening applications right on the labelling on the back of the bag. I paid around $6 for a 40 pound bag.

This message was edited May 21, 2006 11:20 AM

This message was edited May 21, 2006 11:40 AM

Yardenman, thanks for the possible substitution. Worth checking out.