JaRoHe
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Planting in 100% Compost...

Our church organization put in 12 - 4 ft. x 8 ft. raised bed gardens this year to help supplement our food pantry. The local solid waste agency donated a dump truck load of compost for our project (approximately 12 cubic yards).
(NOTE: The compost was still warm (steamy) when we received it.)

I tried to explain that compost is a soil amendment and suggested that we mix the compost with some top soil (or at least add some sand). I was told that the waste agency said that we could plant directly into the compost... even though on their website they stated that you should [url=https://www.solidwasteagency.org/residential-services/compost]"Never plant in 100% compost".[/url]

My question is, are some crops/vegetables better suited than others for being planted in 100% compost?

A couple of observations I've made:
  • root crops like carrots and beets haven't done very well so far (slow growing and thin roots).
  • pepper plants haven't done well... plants remaining about the same size (or very little growth) as when they were planted.
The group is preparing to build another 33 - 4 ft. x 8 ft. raised bed gardens filled with 100% compost.


Thanks,

Jim
You reap what you sow!!!

gumbo2176
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I have "volunteers" popping out my compost piles all the time. They do grow quite vigorously but I never let them go to fruiting because I'm using my compost quite a bit to amend my soil as the crops are replaced with new stuff.

Personally, I feel things will grow very well in straight compost but with my limited supply, I use it more as a supplement to my garden soil. If I got truckloads free, I'd definitely use more of it.

Be aware that filling the boxes with "garden soil" that you can get from landscaping companies is a crap shoot. I got enough last year to fill a raised bed 12 ft. x 4 ft. x 1 ft. tall and even though it looked good and was nice and loose, it was very lacking in the proper nutrients to grow like I was hoping. I amended that box in the late spring with my compost and had better success with subsequent plantings. I'll add more compost in a couple weeks before putting in my fall crop of root vegetables.

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rainbowgardener
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All the volunteer squash plants that start from my compost pile seem to do great there. I have a couple I didn't pull that are spreading like crazy. They seem to love it there.

But I agree with you, it would be better to mix in some topsoil. Compost in a raised bed, over time can compact down and get pretty dense.
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Gary350
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I have experemented with compost for 40 years compost does not have much food value for plants. Everything I read says add top soil to the compost pile. If you want plants to grow in 100% compost you need to add something to feed the plants. What works best for me is mix 50/50 compost and top soil plus some 15/15/15 fertilizer and lime.

I use to get 3 to 5 truck loads of tree leaves from the city every year for my garden. They have vacuum trucks drive around town and suck up leaves people have raked to the street. They put 3 ft of leaves over my whole 40x80 ft garden. I would sprinkle 3 bags of ammonium nitrate over the leaves and by spring the nitrogen had turned the leaves into about 12 inches of what looked like potting soil. I tilled all that into my garden every spring WOW it made some nice soil. But it does not last the composted leaves totally compost away and are gone in 2 years. That was 30 years ago before people started putting toxic poison on the lawn.

I wish I could still get leaves from the city but I would be afraid to eat the vegatables these days 95% of the people around here spray their yard with toxic stuff I do not want in my garden.

Keeping a good supply of compost in the garden is a lot of work. I have tried manure it composts away and its gone to in a couple of years. I have tried 50/50 peat moss and soil too it works great expecially for bell peppers. I'm not sure why bell pepper plants like the pear moss so much my plants often get 7 ft tall and sweet bell peppers are 6" diameter and banana peppers are the size of real bananas.

john gault
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They need to read up on books about soil. I agree you shouldn't plant in 100% compost. Compost may have all the macro-nutrients and some micro, but soil has the rest of the micro-nutrients. And then there's the issue of sturcture.

It's a subject I'm very interested in, but still reading about, thus I can't yet talk too extensively in an intelligent way, so bottom line, have them go read books on soil. One thing I have learned is that Compost is not soil, it's just a constituent of soil. Soil is very complex and has many parts.

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stella1751
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Peppers don't thrive when they have too much nutrition. They like to work for their production. I'm surprised to learn that they have stalled in their growth, though. Generally, over-feeding peppers, as in giving them too much compost, causes lots of foliage and no peppers.

The biggest problems I foresee in additon to what has already been said is that the compost will decay, necessitating refill of the beds each year, and the possible introduction of diseases. I rarely had a problem with disease in my tomatoes before I used a mess of the municipal compost. I haven't had a good tomato year since :x

In fact, that may be why your peppers are unhappy.
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garden5
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Well, I can say that when something pops up in my compost heap, it grows very well!

However, I must also add that my compost heat is AT LEAST 50% dirt. It actually started as a dirt pile that had organic materials added to it. So I think that this supports your theory that pure compost isn't idea.
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soil
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its depends 100% on the compost. some compost will turn to mud when wet. others will act better and be perfect for planting in.
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CharlieBear
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I am curious about the weather and the watering of the box, that is also a very big factor in outcome.
Lasagna gardening is essentially gardening in compost and it works pretty well for many people. I have several boxes that were all filled with mushroom compost and things grew great for the first 3 years. After that I had to amend them to keep yields up. I also have 6 boxes that I filled with my own compost, they also work great except for blueberries that want something more acid.
You only said compost. There are many different sources of compost that can be bought. Some are little more than disease ridden yard debree the city has collected and composted at too low a temperature. Some compost is much higher grade than you might think. It depends on what it came from and how it was composted and at what temperatures.
There was even a company that I knew that composted farm animal waste until it smelled like sweet soil. Everything did well in that, especially tomatoes and peppers.
Disclaimer I am not endorsing straight compost especially without knowing who made it, how it was made and what went into it. I am an environmental engineer with a masters degree, so I have studied these things quite a bit. In this state they allow waste from waste water treatment plants to be composted and used on some otherwise barren land to increase water and nutrients. You couldn't get me within 200 miles of that stuff.

JaRoHe
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Thanks for responses...

I contacted the Solid Waste Agency and they assured me that there was no sewage sludge in the compost. Someone had told me they add some chemical to the pile to get it cooking but I couldn't substantiate that claim, the Solid Waste Agency assured me they don't add anything to activate the pile.

The ingredients are supposedly from curbside yard waste... so you don't know what chemicals might be in the stuff. There are a lot of woody/twiggy particles that have surfaced in the compost as it aged (I assume they float to top from either rain/watering).

Of all of the books I've perused through at the library, not one of them mentions using 100% compost to plant in.
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jal_ut
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Most of us have better soil on our plots already that can be bought.
Soil does not come in a bag. Compost is not soil. Leaf mold is not soil. Potting soil in a bag is not soil. These things may be called soil substitutes or soil ammendments.

Soil is the name for that miraculous thin covering of the earth which is made up of sand, silt, clay, humus, oragnic matter, water, air, chemical substances, and a host of small living organisms. Soil is what makes it possible for the flora of the Earth to grow and prosper. Soil varies in composition where ever it is found.

Real soil grows the best plants. Compost is a soil amendment. I would suggest digging out about ten inches of the soil under the raised beds and then mixing it with the compost as you refill the beds.

May I suggest some reading?

https://en.wikipedia.org/wiki/Soil

This is just a start. The internet abounds with good reading about real soil. Do the research.
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bogydave
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I fill my raised beds with compost. I have learned to mix in some garden soil to help the density of the compost so it will hold moisture better. I use almost done compost (moldy grass leaves etc) in the bottom, then mix horse manure compost & garden compost & garden soil on top of that. But 90% is compost. But my beds are on top of pretty good garden soil so the roots I'm sure reach down that deep later in the summer as the soil temps warm up. I went to raised beds to allow me to plant earlier here, the beds warm up sooner than the garden soil in the spring so I can plant 2 -3 weeks (+/-) earlier than when I just made raised hills/rows from a roto-tilled garden.
Now I don't till & have better weed control between the rows.
I experimented with pure 100% Horse manure compost, 100% garden/grass leaves compost, a mix of the 2 & added some garden soil. All plants did ok some did well & I found moisture retention the biggest problem with 100% compost. Now I add about 3" of new compost to the top of the beds each spring, use a pitch fork to mix it in & then walk done the mix to make it tighter soil & it hold water better. This year it did exceptionally well so after a few years of different mixes, I think I have one that works well for me.
I guess I use "garden soil" to amend "compost" since my beds are 90% compost. The soil in the beds has become finer ( the compost continues to break down more over time) & is holding moisture better now after a few years & earth worms have move into the beds.

This is my 3rd year with compost filled raised beds & has been the best garden ever. Each year the soil level (volume) in the beds have shrunk so the compost is breaking down & I add new compost to the beds in the spring to get them filled up.

Picture of filling a new bed with compost this spring, (16 ft 2X12s) almost done compost on the bottom , adding garden compost, then I'll add horse manure compost on top of that & shovel in a little garden soil. Then I mix it up, water it down real heavy & walk it down to compact it. It sets about a week before I plant in it.::
[img]https://i274.photobucket.com/albums/jj269/bogydave/rbsoilmx.jpg[/img]

My compost experiment this year is mixing fish carcasses & remains with horse manure compost & composting it . Hoping for even better results if it is ready next spring so I can mix it into the beds. So far so good with it.

If you use 100% compost, mix in some garden soil or just dirt to help it be a tighter soil, walk it down to compact it.
Working great for me. I haven't told my plant they ""can't"" grow well in compost, & by the results this year I know they like it.
I've froze up more & bigger broccoli than ever, given away so many zucs, froze up several quarts of beets with another bed to pick & the carrots are doing great, lettuce, spinach, kohlrabi, turnips, cabbage, peas, beans all did & are doing great. My Greenhouse likes it too (soil boxes in it are compost mixed with perlite & some sand).

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jal_ut
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Roots

But my beds are on top of pretty good garden soil so the roots I'm sure reach down that deep later in the summer as the soil temps warm up.
Anyone interested in growing vegetables should take the time to read this paper about the development of roots. It is very informative.

[url=https://www.soilandhealth.org/01aglibrary/010137veg.roots/010137toc.html]Click Here[/url]
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john gault
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This link is pretty good at giving one an appreciation of soil. And illustrates well why you shouldn't grow plants in 100% compost, some may grow, but not getting all the nutrients needed. Also most people don't' have an appriciation of the importance of rocks in soil. Yes rocks do provide nutrients and rocks aren't just broken down by the mechanical forces of weathering they are also biodegradeable.

Very interesting stuff https://www.globalchange.umich.edu/globalchange1/current/lectures/soils/soils.html

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jal_ut
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Good Read john gault. Thanks for the link.
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2cents
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I've been successful at growing in 90+% organic material(compost).
A very thin layer(1/2") of clay on top of the will help the process, hold moisture, so plants don't topple over as much.
See the permaculture forum....hugelkulter beds.

tomc
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JaRoHe wrote: Someone had told me they add some chemical to the pile to get it cooking but I couldn't substantiate that claim, the Solid Waste Agency assured me they don't add anything to activate the pile.
If anything was added, it was most likely urea. This is done with things like mushroom compost to get the N higher and pile cooking quicker.

If there are problems in my experience with 100% compost, it is roughly the same as with 100% peat moss in beds. Once wet, it stays wet. Once dry it stays dry.

Its August here in SE-OH and has been a bit dry. A dried out bed filled with all compost can be quite hydrophobic, and a real pain in the asterisk to get the bed to take water in.

If I have a long term reccomendation it is compost will continue to break down and it will loose its fertility. Establishing a composting system close to your beds to add mostly, but not quite completely composted yard waste will make your garden and resulting crops better.

Even if no urea was added, mechanically made compost tends to collect salts and just doesn't give back the tilth I think you want. Those little bits of lignin and other high carbon bits are the fodder of micro-herd you want to keep pooping back into your garden.

if you scoop up some dirt, how many worms are in each shovel full? There should be some. Will dirt ball up? the absence of either (or both) is an obvious showing of lack of tilth.

I'd fill beds built about now for next year with leaves or spoiled hay. let providence cold compost it to dirt over the winter.
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