Can I or can't I use 100% compost in my raised beds?

[annafaie]

This whole time I thought I was composting so I would have the rich "soil" I needed to fill my raised beds with.

Yesterday I read somewhere that you're not supposed to grow veggies in 100% compost??? Is this true?

[hendi_alex]

Mine are almost 100% compost, aged manure, synthethic potting soil, with very little actual dirt. They seem to produce very well.

[2cents]

Watering issue.......

I've grown in straight compost as long as part of it is well composted. 1 year plus in slow compost pile, mostly leaves.
There have been ones with fresh wood as the base material, Then new compost and finished with old compost.
This works for bush beans, maybe not alot of other plants. Put onions in late in the 1st growing season of straight compost.
A cover crop in the fall before will really help.

The problem I found is that is doesn't hold water well, too much drainage.

It required too much supplimental watering, it was a chore.

Working a little of my hard clay or good dirt in the top helps a bunch the first year.

It really only takes a 1/4 to 1/2 inch of real dirt to amend the compost help hold the water.

Year two, my compost is mostly dirt. I add more compost to keep the beds up to the top of the frames.

[Timlin]

Anna I only use straight compost in growing my squash and that's because I plant my squash directly into the pile that's not finished and ready to go into the gardens.

In the rest of the garden I put a good thick layer of compost over the soil and mix it in. I use as much as I possibly can spare but certainly it's not 100% compost; I wouldn't think it's 50% compost.

How do you ever have enough compost to be able to fill your gardens with only compost? How I'd love to have that much compost to use......I'm always short of what I'd really love to have in the compost area.

[cynthia_h]

Mel Bartholomew, developer of the Square Foot Garden concept, recommends 100% compost for growers in less developed countries. They have access to or can make compost; they don't generally have access to, or funds to purchase, the other "ingredients" of his planting mix (vermiculite, compressed peat).

So...it looks to me as if you *can* use 100% compost; what are the circumstances where you feel you *must*?

Cynthia H.
Sunset Zone 17, USDA Zone 9

[jal_ut]

I would not use straight compost. The benefit of compost is in large part to add nitrogen to your soil. Compost by itself is too hot for growing plants. Compost also adds humus to the soil which is beneficial.

My experience tells me you are better off planting in topsoil that has been amended with compost. Topsoil is that wonderful layer of material that has been laid upon the earth by nature. It is full of minerals, and organic matter and miniature organisms that make it a living breathing miracle that will grow plants better than anything else. If you want to grow something start with topsoil and amend it with compost.

Try a little test. Get four four inch pots. Fill one with sand, one with topsoil, one with compost, and the last one fill with two parts topsoil, one part sand and one part compost mixed. Now plant two bean seeds in each pot and water. Put the pots in a sunny spot. When the seed comes up you will promptly see which material will grow the best plants. Report after three weeks.

Edit to add: Real compost is made by assembling a large pile of organic materials in such a way that it will cook. It only takes a week or so to make compost in a good hot pile. What you have then is a nutrient rich material that is very high in nitrogen and other plant nutrients, plus humus. Use it now to amend the soil before you lose the nutrients.

I fear a lot of what people call compost is organic matter that may have been broken down by bacteria, but it has been in the weather for a year or more and the nutrients have mostly been leached out. What is left is humus.

[jal_ut]

I suggest this reading on Wikipedia: http://en.wikipedia.org/wiki/Compost

Then also look up humus.

[veggiegardener]

You can use 100% compost but you will have to water more which sucks. But you can do it, I don't think theres anything too wrong about it but then again I could be wrong. I had no problems

[Jbest]

I am a compost freek. Everything I grow is in 100% homemade compost including hanging baskets. Don't go by the experts, I do not think they ever had a garden let alone a compost pile.

John

[Timlin]

John you must be gardening in a very small area. How can you possibly cook enough compost to grow everything in 100% compost?

I have almost an acre of veggie and perennial gardens......I have piles of compost in the yard and borrow/beg from the neighbours horses but I use up every drop of compost and never have enough to go around.

[Timlin]

JOhn I totally enjoyed the visit to your site. I'm in a much colder area than you are BUT I don't mulch everything down that tiny before building my compost piles.

I build a huge pile in the fall, turn it in the spring and add all the kitchen scraps from over the winter and plant my squash into the pile......it's not ready to spread around until the squash is finished in the fall so it's a slower process.

I love the raised bed system you just built. You're going to enjoy that this spring. We put in 3 new raised beds last fall but I think I'm going to convert a couple of our in ground beds to raised and escape the tree roots we battle.

Great site! Fun entertaining reading for February in the north.

[smokensqueal]

annafaie: Your question can be answered in many different ways. Compost is different to all people. Some is a mater of breaking down material in a few weeks others are a year or more. The one trial the other person suggested would be good but each batch of compost is going to be different then then next or last. If your compost is comprised of 3 or 4 items I wouldn't try to grow anything in it at 100%. But if you have a very good mixture along with very little non composted material then you could certainly use 100% compost.

But like other have said do you really have enough compost to use only that? I also would love to have that much compost.

Compost in general is typically best used as and amendment to the soil to enrich the soil. Soil has things your compost doesn't and compost has things your soil doesn't. Can you grow in just soil? Sure can. Can you grow in just compost? Sure can. But typically the best is to mix them.

[a0c8c]

I've done both with great success. Most things I mix half compost, half dirt(I won't call it soil yet) but I've grown things in all compost before. With the heat that we're gonna get, I doubt I'll do much in 100% compost this year, otherwise I'll be watering 4 times a day.

[tedln]

I bought a six cubic yard dump truck load of compost this past summer. It was made from horse bedding which consisted of saw dust, horse manure, and horse urine. The compost had aged and matured for about 18 months before I got it. It looked like a very rich loamy soil. I decided to experiment a little late last summer and tried to germinate some different seeds in the compost. The seeds would germinate fine, but the plants would slowly wither and die. The compost seemed to not have all the components necessary to make plants grow healthy. The pile has now composted through another winter. I used almost half of the compost mixing it with normal soil and letting it weather and mature in some raised beds this winter. I think it will work well mixed with the soil.

Ted

[garden5]

I bought a six cubic yard dump truck load of compost this past summer. It was made from horse bedding which consisted of saw dust, horse manure, and horse urine. The compost had aged and matured for about 18 months before I got it. It looked like a very rich loamy soil. I decided to experiment a little late last summer and tried to germinate some different seeds in the compost. The seeds would germinate fine, but the plants would slowly wither and die. The compost seemed to not have all the components necessary to make plants grow healthy. The pile has now composted through another winter. I used almost half of the compost mixing it with normal soil and letting it weather and mature in some raised beds this winter. I think it will work well mixed with the soil.

Ted

That sounds like "damping-off," which actually covers several diseases seedlings can get when there is too much moisture and not enough drainage. Did your compost hold water very much?