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How much vermiculite/perlite

Posted by tudorrose 9b (My Page) on
Fri, Nov 3, 06 at 11:53

I'm about to put the soil/compost mix into my raised beds and from a previous posting was advised to add perlite or vermiculite for drainage. I was told about of each component but that would be about 60 cu ft of vermiculite and thats rather spendy. Could I get away with less? My raised beds will be filled about 2.5 feet deep with new soil/compost/vermiculite mix as the original soil was removed to add to the area that became patio (needed to raise the level).

What are poeples thoughts, FYI I'm in AZ so it gets hot here and keeping soil workable is a must.


Follow-Up Postings:

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RE: How much vermiculite/perlite

A new old debate, I don't think perlite, vermiculite, sphagnum or any of the things people use in pots has any value in the soil.
A raised bed automatically has drainage!
Listen carefully to those who use these things and they will offer things like "I used this or that and it worked out well" without a reason why.
I say they dont help because they do not contribute to the organic matter or support the soil organisms. In pots the soil organisms are very limited so all the important things they contribute in the soil is lost and we must try to create conditions that will support growth in pots.


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RE: How much vermiculite/perlite

I agree. Vermiculite/perlite/pumice are entirely unnecessary in a raised bed and are a considerable expense. These are products that should be used exclusively in container soils where heavy garden soils are inappropriate and where very sharp drainage is required. As mentioned, raised beds by definition offer superior drainage than inground planting conditions. A good quality soil/planting mix - I hesitate to recommend "topsoil", as that can have an infinite range of variables, including being a bunch of crap soil - which can be augmented with compost or other organic matter, if not already included, is all that is necessary.


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RE: How much vermiculite/perlite

As the others said adding vermiculite or perlite to the soil of the raised beds is unnecessary, and as you indicated it will be really pricey. In Arizona you may not be able to get enough good organic matter to add to your soil and may be reduced to having to use peat moss in which instance add an equal amount of manure because peat moss has no nutrient value and you need something with it. But you need to get organic matter into your soil, if its clay that will open up spaces between the soil particles and allow moisture, nutrients, and air to get to the plant roots and if you have sand that OM will hold moisture and nutrients in the root zone long enough fo rthe plants rotos to use them.


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RE: How much vermiculite/perlite

You shouldn't need any in a raised bed. BTW Vermiculite is added to hold moisture and act as a fertilizer carrier not for improving drainage. :D

Vera


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RE: How much vermiculite/perlite

I would fill them differently depending on what I planned to grow. For example: potatoes like sandy, well-drained soil without a lot of organic matter (and no manure please!) However, a very rich, fertile soil might work better for a "salad" type crop.

However, I don't know what you plan to grow in Arizona? Tomatoes? Peppers? Corn? Warmer season stuff?

If you want a good soil that would work for multiple crops and you need a large amount, why not check with a locally-owned garden center (not a big box like Home Depot) and see if they'll deliver a truck load of a nice blended mix? It would likely be both less expensive and more appropriate for your area/climate.

Sorry I couldn't be more help on your specific vermiculite/perlite question.

-C


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RE: How much vermiculite/perlite

I'm guessing here that you were intending this 60 cubic yards of vermiculite to comprise 1/3 your compost/soil mix.
That would suggest your bed would be about 2000 square feet...approx. 40 X 50 ..in that range.
Such amount would indeed be quite pricey...the other 120 cubic yards of the soil/compost would be very expensive.

The vermiculite for your purposes is not necessary if your compost/soil mix is anywere decent in its make-up.
Vermiculite is a very good drainage material for use in containers.

Your bed's make-up would largely depend on just how much amending it will need. Arizona I would hazard is largely an area where sandy soil may be the usual...seeing as how the desert south-west has such make-up.

The forested areas would have its degree of organic matter...but still I'd say not heavily so.
So you would have to add to any soil you presently have as much organic matter as would be necessary for good drainage, yet good holding capacity of mositure.

Your choice of what constitutes the compost would decide how much soil is mixed with it and whether you need to add any peat moss (to retain moisture and give your soil some body) and/or sand to aid in drainage capability.

The degree of organic matter would then depend on just what kind of compost you intend to purchase.
You can then add to it amendments to improve the organic content to satisfy your needs. Vermiculite is not one of them.


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RE: How much vermiculite/perlite

Vermiculite is a mica like material that is heated so it expands many times its origianl size. Since it is used as an insulation it shold not hold any moisture, something we o not want insulation to do since that inhibits the materials ability to insulate. Vermiculite is an inert material and therefore has not nutrient value.
Gardeners use this expanded mica like material to improve drainage in soilless potting mixes where it is fairly easy to achieve the 10 percent needed. To get a 10 percent mixture in your garden would probably be cost prohibitive.


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RE: How much vermiculite/perlite

I would guess you've already visited the square-foot gardening forum, but if not, you should. The official SFG method calls for 1/3 compost, 1/3 peat moss, and 1/3 vermiculite/perlite.

I started with SFG and out a year ago and was similarly scared by that amount of vermiculite and ended up using it as only about 1/8 of my total mix. I can't say if it makes any difference, but my beds do drain very well.

I would caution against using peat moss if you were considering it, particularly in your hot climate. In our hot weather last summer I could not keep the soil wet enough and the peat dried out completely.


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RE: How much vermiculite/perlite

Vermiculite turns to mush if compacted. One more reason not to use it....in containers or otherwise.


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RE: How much vermiculite/perlite

Boy, everyone sure is down on vermiculite ;-)

Personally I like the stuff in raised beds. I am one who uses the Sq Ft Mix for raised beds and am very happy with it. It (vermiculite) doesn't 'turn to mush' in my beds, but then again I don't walk on my raised beds to compact them ;-)

Anywho, I agree that it isn't necessary in a raised bed and considering the amount you would need I would skip it. I am just not as down on it as some are ;-)

Given your (the OP) warm zone in AZ I would suggest going with something that retains water very well since the bed is raised and you have to deal with hot sun. In fact I would bet sunken beds are more common than raised in your area.

I have only been to Kingman, AZ and the surrounding desert so I don't know how that compares to your part of AZ, but if it is at all like Kingman I would be using 50% clay, 30% compost and 20% chopped leaves on top to retain moisture. And this would be in a sunken bed, not raised.


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RE: How much vermiculite/perlite

Can someone clarify where the square foot gardening forum is? Is it on this site or a different site? I just bought his book and have so many questions. A forum is exactly what I need!!!!


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RE: How much vermiculite/perlite

The square foot gardening forum is on this site, but there are different commercial sites where there are also discussions of square foot gardening.

Here is a link that might be useful: Square Foot Gardening


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RE: How much vermiculite/perlite

The Square Foot Gardening foundation sponsors a web site that is very active and dedicated to square foot gardening.

I just love the square foot gardening method and the soilless planting medium.

Here is the link.

Here is a link that might be useful: Square Foot Garden link


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RE: How much vermiculite/perlite

Thank you Yolos and Lucile! I just registered for it!!!!


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