Purpose/advantages/disadvantages of container ingredients
 

I personally don't use the self-watering containers, I just grow my tomatoes in 18 gallon tubs. In the past, I've used a mix that worked for me, but isn't generally considered very good I believe (1/3 composted horse manure, 1/3 peat, 1/3 topsoil). I was thinking of modifying my mix some this year. I probably will not be buying the soil-less potting mixes, that's just too expensive for me. So I was wondering, that purpose the various ingredients have, and the advantages and disadvantages of each.

So here's my guesses and some questions - please correct me where I'm wrong.

Topsoil - nutrients for plants. Disadvantage - compacts. Inexpensive

Composted manure - same as topsoil. Additional disadvantage - weeds.

Mushroom compost - same as topsoil, even more nutrient-rich

Peat - nutrients. Holds water. Compacts?

Bark fines - aeration. Does this use up nitrogen though?

Vermiculite - aeration. Kind of expensive

Other ingredients - ?????

Perlite. Adds air space and drainage, relatively inert and a natural product. You can get a 4 cu ft bag for around $20 from a hydroponics store, may be larger amounts available.

Topsoil - nutrients for plants. Disadvantage - compacts. Inexpensive
[COLOR="Blue"][B]heavy, generally does not drain well in a container[/B][/COLOR]

Composted manure - same as topsoil. Additional disadvantage - weeds.
[COLOR="Blue"][B]yes, same disadvantages as topsoil. However, I've put an inch or two of composted manure on the very top of the potting mix (once it's settled) and it provides a good source of nutrients over time.[/B][/COLOR]

Mushroom compost - same as topsoil, even more nutrient-rich
[COLOR="Blue"][B]mushroom compost is derived from the mushroom growing medium which is generally peat with added straw and lime. It is lighter than topsoil, is relatively inexpensive if purchased in bulk, but can be high PH, so be careful how much you add.[/B][/COLOR]

Peat - nutrients. Holds water. Compacts?
[COLOR="Blue"][B]good water retention and a valuable ingredient of most mixes. No nutrient value and generally low pH.[/B][/COLOR]

Bark fines - aeration. Does this use up nitrogen though?
[COLOR="Blue"][B]excellent ingredient that generally makes up at least 1/3 - 1/2 of my mixes. No nutrient value, good aeration. Pine bark fines will not tie-up nitrogen, but be careful of what you purchase, because I've seen bags of "fines" which actually include a fair proportion of shredded hardwood, which will tie-up N.[/B][/COLOR]

Vermiculite - aeration. Kind of expensive
[COLOR="Blue"][B]perlite serves the same purpose and will hold up longer than vermiculite. Not sure about comparative price, but I get a very big bag of perlite for about $15[/B][/COLOR]

Other ingredients - ?????
[COLOR="Blue"][B]Turface, Pros Choice and other calcined clay products, most often marketed for ball field conditioners, are excellent additions to potting mix. I get Pros Choice from a nearby John Deere Landscapes retailer, but I'm not certain of their distribution.[/B][/COLOR]

If that worked for you use it. Top soil in a container doesn't drain for me and did not work. I tried compost in a big stock tank that also didn't work. I use potting mix in my pots because it drains well and plant roots reach to the bottom. If I tried your mixture it would be soggy here.

I used top soil my first year out of ignorance. I had a good haul of tomatoes, but it did compact as the season went on, and was slow to drain. I'd have to water, let it settle, water some more, let it settle, etc.

Thanks so much everyone.

I must have some sort of dumb luck, because it drained fine for me. Dunno.

I thought mushrooms were grown in composted manure - apparently that's incorrect?

I'm talking about 32 containers, why I'm being "cheap" and not just getting a mix (also not too enthused about things purchased in bags)

The local place sells a bulk mix of topsoil, mushroom compost, and sand - that's intended for the garden itself though, not containers. I was considering that however, plus adding some peat and bark fines though, if I can find them.

Or just doing the topsoil and mushroom compost (I can get both in bulk) and adding peat and fines.

I realize it's not considered ideal - but hopefully doesn't sound like a disaster?

The mix that I've used with good luck is peat, pine bark fines and perlite. My basic mix for each of my containers (2' X 4' X 18") is:

6 cu. ft. pine bark fines (i.e. 3 bags)
10 gal perlite
10 gal peat

lime
3 c. balanced organic fertilizer
1 c. greensand for micronutrients

Interesting, so that's WAY more aerated than my mix. I need to find stuff I can buy in bulk, I'll have to run down the road one of these days and see what's available.

If I don't have problems with drainage, which I don't, how do I know if the mix I'm using is causing any problems? I can see it's probably not the best aeration - but what difference would more aeration make?

Tam - when I first sought information on how best to compose a container mix, I found this thread on Gardenweb: [url]http://forums2.gardenweb.com/forums/load/contain/msg0316064615891.html?70[/url]

Tapla (Al) is a Master Gardener and his thoughts on container gardening are very instructional. I think you'll find it useful. I don't frequent GW very often, but I keep a printed copy of this thread in my garden journal so I can refer back to it periodically.

Thanks, I'll go have a read.

I buy mushroom compost from Miami Oklahoma. It has chicken manure in it and what looks like grass or hay. I have rotten straw bales around and what is in the mc is not stemy like straw. I use it for a mulch because it doesn't have weed seeds. I wouldn't even try it in a pot except a little on top, but I would put it in a raised bed. The materials you are using would work in a raised bed. How I would know if it wasn't working is the plants would die. If they live and you get tomatoes you did well.

Matilda, it sounds like you have a source for the good mushroom compost. The stuff in the bags is useless because it packs too much and has little organic structure left in it. I used to have a source for the mushroom compost made with straw and chicken manure and gypsum. I used it alone in some pots and grew tomatoes in it and they did better than any of the soil less mixes I have tried since then. It stays rather loose and drains well while feeding the plants good. If you have some why don't you try just filling a large container up with the mushroom compost and plant one tomato plant in it and see how it does. I think you will be pleasantly surprised.

It smells like it would be super fertile when it is "fresh" but I will try it. I actually plant most of my tomatoes in the ground. I have lots of plants in pots because of trees in my yard so I buy too much potting mix. I have made some with perlite, peat and pine bark fines also.

[quote=fortyonenorth;208402]Tam - when I first sought information on how best to compose a container mix, I found this thread on Gardenweb: [URL]http://forums2.gardenweb.com/forums/load/contain/msg0316064615891.html?70[/URL]

Tapla (Al) is a Master Gardener and his thoughts on container gardening are very instructional. I think you'll find it useful. I don't frequent GW very often, but I keep a printed copy of this thread in my garden journal so I can refer back to it periodically.[/quote]

Wow! I learned a great deal, reading that! Thank you forty for sharing. I am just a second year gardener, but I feel I have made enough mistakes to have been doing this wrong for ten years!
:shock:

"Topsoil" has a lot of variability in how much native gravel
is in it. That could account for differences in drainage.

This document has a lot of useful information on what
makes a good container mix:
[url]http://edis.ifas.ufl.edu/cn004[/url]

Interesting, any topsoil I've bought here just has black dirt. No gravel or anything.

I'll go read that link, thank you.

I'd like to second the referral to Al's threads! I had NEVER been able to keep anything alive before I discovered his advice... NEVER! So, that's what I use in my containers: Al's mix! In one of the threads he specifically talks about tomatoes in containers, but I couldn't tell you which one... GW's not terribly "search friendly" when it comes to loooooong threads!!! Add to that the fact that he had/has to keep starting new ones and there must be a series of 50 or so!!!!!!

I am using compost from the local university's ag center. (some Universities and many cities now have affordable compost and mulch that can be purchased.)
Here is there link as an example [url]http://www.wku.edu/farm/mulchyard.html[/url]

I got a mix of the leaf mulch and sawdust/manure mix they have listed it was $125 for 6 cubic yards.

I will also be getting a load of top soil as well. Top soil though is kinda a lose term as the quality of top soil can vary greatly. Here cheap top soil would be mostly clay and rocks (lime stone). The top soil I am getting as soon as its dry enough for the guy i am getting it from is river basin soil that will also be shifted to remove most any rocks. (soil from the flood plain of the river bank) this will be 10 cubic yards for $165

I have a lot of beds to fill up etcetera, so that is the reason I am ordering it by the dump truck load.

Both prices I quoted in this post included delivery to my home. For reference 1 cubic yard = 27 cubic feet. If you notice most soils and mixes at the box stores say covers 2 sq feet but that is at a depth of 6 in so really they are 1 cubic foot in size.

So 1 cubic yard = 27 bags of top soil or potting mix.
So 16 cubic yards (16 X 27) = 432 The total price was 125 + 165 = $290 290 DIVIDED by 432 = 0.672 so roughly I am paying $0.67 cents for a bag like in the box stores for my mix I am using.

I guess the point I am making is you can look around your area and might be able to find similar compost and or top soil and get better quality while saving a lot of money. You usually can buy by the pick-up truck load as well if you do not need as much.

The above mix is comparable if not better in my opinion than MG potting mix and a whole lot cheaper.

Pricewise, I think you're making out even better than you think. Most of the bags of stuff at the big box stores are only .75 cubic foot as I remember.

Bark fines in my experience will not use up alot of N, as long as they are aged just a bit. I only use three ingredients in my container soils, fir bark fines, peat and perlite (and some lime and a complete fert). In a ratio of 5-1-1 respectively. It Drains fast and holds just the right amount of water. I love this mix!

Damon

So far I haven't found a source for bulk bark fines. So I seem to be back to my original mixture, since it's worked ok for me before (topsoil, composted horse manure, and peat). It seemed to hold the water fairly well, and I didn't have a problem with drainage (I use an 18 gal container per plant).

But I have to get the soil from one source, and the horse manure from another, and I'm trying to avoid paying 2 delivery charges. So I'm considering another couple of options:

1. topsoil + mushroom compost + peat
2. mushroom compost + peat
3. composted horse manure + peat

I think I've been hearing that the horse manure is better than the mushroom compost.

I've also seen info of growing tomato plants in just a bag of manure/compost - so I'm thinking perhaps the topsoil isn't bringing much to the party, and I should just eliminate it.

Any thoughts?

The topsoil probably provides trace minerals (calcium, sulfur,
magnesium, iron, manganese, boron, molybdenum, etc), in
forms that are already available to plant roots. If you are going
to do without it, you may need to add some other sources of
minerals, depending on what you use for fertilizer.

I'm a firm believer in using *some* compost in containers. I realize this is a somewhat controversial belief.

Ah, so we're saying the trace minerals in the topsoil would be missing in the manure or mushroom compost?

My experience with most "topsoil" is it's dirt that has been scraped off a lot, with no redeeming qualities whatsoever. There is no legal definition. Of course your mileage may vary.

Waaah, no one agrees :cry:

Need topsoil for minerals / topsoil useless
Mushroom compost better than manure
Manure better than mushroom compost
aaak

Given the choice, I'd opt for #3, assuming it is, indeed, well-rotted horse manure. Without the fines, though, you really should add something to improve the drainage, e.g. perlite.

In terms of the bark fines, you might try K-Mart - my local store carried PBF last year. I've also seen it at Menard's and Home Depot, but I imagine you've checked those options.

I'm sure I can find the bark fines - it's paying for enough to do 30 containers worth...

The thing is (and I don't mean to be obstinate here) - with my topsoil/manure/peat combo, I'd water the plants, the water would drain out the bottom holes, and it'd stay moist enough until the next morning. So it didn't seem like there was any problem with drainage - at least not that I figured out.

Is there something I'm missing? What would be the sign of inadequate drainage, and the need for bark fines/etc?

I'm not saying I'm right or anything - everyone seems to think it would be a problem. Which I accept - except my plants grew fine. How would I know? Wilting? Lower production? ....?

A more porous mixture will provide better drainage and also more airspace for root development. If the heavier mix works for you, it's hard to argue with success. Maybe pickup a bag of bark fines and a small bag of perlite and mix-up just one of your containers to be lighter - then you can compare them side-by-side.

A scientific description of optimum container media makeup
in terms of water-holding capacity vs air space:
[url]http://edis.ifas.ufl.edu/cn004[/url]

Figure that composted horse manure is compost, with a little
higher than average N-P-K for compost (it has had plenty of
nitrogen from the beginning, with only small amounts of
high-carbon material like shavings or straw in with it). Peat and
composted horse manure would make a nicely aerated,
well-draining mix for the first summer. After that, the horse
manure will turn to silt as bacteria break it down more
completely. Silt is too fine to be useful in a container. It fills
air spaces that the plant needs.

Composted horse manure has some minerals, but it typically has little calcium in particular. and it may be low in iron and
magnesium as well (depending on the diet of the horses).
The mineral content of peat moss is so low as to be insignificant.

Bark fines take some years to break down, so they preserve air
space and drainage longer than compost. Peat moss takes about
5 years to break down completely to silt, which is why most
container mixes use a lot of it.

YMMV on topsoil. Some of it is excellent soil excavated from
bottomland along rivers and creeks, basically sandy loam,
with a fair amount of organic matter from annual additions
of leaves and dead weeds and grasses rotting on top of it.
It grows vegetables well all on its own in gardens, raised beds,
etc, with just annual additions of N-P-K to replace what gets
used up by crops and washed away by rain. Mixing in or
mulching with more organic matter each year (leaves,
compost, cover crops, manures, etc) keeps it healthy and
productive.

Other "topsoils" are just as Feldon described, "fill dirt" in a bag
on a shelf at a store or in a big pile somewhere.