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?

[tedln]

garden5,

Yes, it may have been damping off. I planted cucumber and summer squash in the 100% compost just to see if it would support plants. I planted them really late in the summer when the day light hours were a lot shorter. The cucumbers germinated and grew 8 or 10 inches before dieing. One plant even put out a few blooms before dieing. Less than 50% of the squash even germinated. The ones that did germinate grew a couple of inches before dieing. I haven't decided if the compost simply wouldn't support them in the 100% strength or if the plants I chose were simply not appropriate for the late season in which they were planted. I'm thinking about putting a wheel barrow of compost in a pile in one corner of my garden this spring and planting some stuff in the compost pile just to see what they will do.

Ted

[Jbest]

On the right are Butterbush squash and on the left are potatoes. All are growing in 100% compost. The potatoes exceeded 4' high before harvest. John

[tedln]

Hi jbest. I love your journal. I also appreciate your thoughtful approach to gardening. I was aware that you are growing in 100% compost. I think your compost is more chemically and nutritionally balanced than my purchased compost. Given time and the possible addition of some micro nutrients my compost and those like mine will eventually be as balanced as yours.

Ted

[Ofer]

I once did an experiment for a big nursery for new varieties of lawn.

I used to have a big plot so we had 10 sq/m of 4 varieties X 2

All of it was grown on just compost! My lecturer from Uni was the organizer of that. true I was surprised too. But it is actually great.

If the compost is not new- no problem.

[gixxerific]

If I can afford it I will be getting about 4 yards of compost for my garden, yard, flower beds. So I hope it is good to use a lot of it because that is what I will be doing. The compost should be good if the Mo Botanical Garden are cool with it than I am too.

This shall get me going to where I can be at least mostly self sufficient with my own compost. I don't see any reason all compost would be bad, what is good soil but degraded vegetation and what is compost, the same so.........

Of course if you want to be more fungal a good leaf mold would do better than a greener compost.

[Joyfirst]

I grew things in raised beds made mostly with compost(square foot gardening recommneded) and things grew nicely. Next year I added composted horse manure and it grew even better. I thought it would be just large leaves and not much fruit, but it was both. My community garden neighbours actually asked me what do I put in my soil!

[Halfway]

Hi jbest. I love your journal. I also appreciate your thoughtful approach to gardening. I was aware that you are growing in 100% compost. I think your compost is more chemically and nutritionally balanced than my purchased compost. Given time and the possible addition of some micro nutrients my compost and those like mine will eventually be as balanced as yours.

Ted

I believe Mel suggests using multiple composts from dealer sources to achieve a balance. This makes sense if the compost is made of one or only a couple different ingredients such as horse manure and sawdust.

Yard waste and kitchen scraps gathered and composted throughout the year would naturally provide a much more balanced compost.

I will be supplementing the beds with potting mix this year as I do not have enough compost ready. It will look to be around 15% compost, 25% vermiculite, 25% peat, and 35% potting soil.

[gixxerific]

Variety is definitely good, and remember all that variety eventually becomes more or less compost. So the more the better.

Compost on!

[jal_ut]

The seeds would germinate fine, but the plants would slowly wither and die.

This is a classic case of the soil being too HOT. In other words too many available nutrients in the mix. (this is also the reason you have to water straight compost beds so much) If you can take a mix like that and add it as an amendment to real topsoiil at a rate of about one part compost to 5 parts soil, then you have something that will grow plants.

[jal_ut]

On the right are Butterbush squash and on the left are potatoes. All are growing in 100% compost.

What is under your beds? Do you have any idea how deep your plants roots go?

http://www.soilandhealth.org/01aglibrar ... 37toc.html
Every gardener should look at this page.

[jal_ut]

BTW this is what squash grown in real soil looks like.

[Jbest]

BTW this is what squash grown in real soil looks like.

Sorry jal_ut but it makes a difference on the weather, how long the squash were growing and what type of squash. In the photo below the bed is 10" deep, 40" wide and 14' long and the 100% compost produced 29 squash averaging 1 1/2# each. Also our weather last summer was the worst growing weather I can remember, cold and few sun days. John

[jal_ut]

John,

My reason for giving you the link to a paper on plant roots was so that you could see that the roots of squash can go as deep as 6--7 feet and as far as 12 feet or more lateraly in all directions.

The point is that you may say you are growing in 100% compost but truth be known, that little bit of compost is only a drop in the bucket of what area your squash roots will gain water and nutrients from.

Unless you have a bottom on those beds to keep the roots from going further? Basically, what you have done is provide a good mulch on top of the ground your beds sit on. Your plants will get a good share of their nutrition and water from the area below and beyond your compost.

Does this make any sense, or will you still say you are growing in 100% compost?

[Jbest]

John,

My reason for giving you the link to a paper on plant roots was so that you could see that the roots of squash can go as deep as 6--7 feet and as far as 12 feet or more lateraly in all directions.

The point is that you may say you are growing in 100% compost but truth be known, that little bit of compost is only a drop in the bucket of what area your squash roots will gain water and nutrients from.

Unless you have a bottom on those beds to keep the roots from going further? Basically, what you have done is provide a good mulch on top of the ground your beds sit on. Your plants will get a good share of their nutrition and water from the area below and beyond your compost.

Does this make any sense, or will you still say you are growing in 100% compost?

How would you explain the success that people have with the SFG style of gardening. Some of which are on concrete driveways or with bottoms and elevated on legs for the patio? Most of them use a soilless mix or straight compost and they have very attractive harvests. Or potatoes grown in bags of commercial potting soil and other container gardens. John

[tedln]

My raised beds had about 10" of compost/soil mix in them last summer. In two 8'X4' beds, I planted my yellow crook neck squash plants along the edges with my tomatoes in the center of the beds. I harvested more than one hundred lbs of squash during the season. Some of the vines were so long, I tied a rope to the outer ends and lifted them to the upper rungs of my tomato cages just to keep the squash off the ground.

At the end of the season, I pulled all the squash vines and tossed them on my compost piles. I found all of the vines were very shallow rooted with none of them extending more than eight inches into the soil. I guess they may have the ability to extend very deep and spread wide, but if they are receiving all the moisture and nutrients they need in the prepared soil, they simply don't extend very far.

They may also have realized that the natural "soil" under the raised beds is very rocky, hard, and nutrient poor.

Ted

[tedln]

The seeds would germinate fine, but the plants would slowly wither and die.

This is a classic case of the soil being too HOT. In other words too many available nutrients in the mix. (this is also the reason you have to water straight compost beds so much) If you can take a mix like that and add it as an amendment to real topsoiil at a rate of about one part compost to 5 parts soil, then you have something that will grow plants.

Interesting thought! While I was thinking along the lines of insufficient nutrients, you believe the opposite. I do remember once reading a thread in a compost forum that said a high wood content in compost will severely reduce the available nitrogen while the wood is decomposing. Since my purchased compost was primarily saw dust with horse manure and horse urine, I kinda lean to the insufficient nutrient side. I will know better this spring when I plant my spring garden and see how the new plants do in the compost.

Ted

[jal_ut]

It is easy to make a test. Take some real soil, some sand, and some compost. Get 4 4 inch pots. In one put soil, in one put sand, in one put compost, and in the fourth use a mix of one part of each soil, sand and compost. Now plant 2 bean seeds in each pot. Water and put them in a sunny windowsill. Water as needed, and see how each mix works to grow the plants. Then decide for yourselves.

[farmerlon]

On the right are Butterbush squash and on the left are potatoes. All are growing in 100% compost.

What is under your beds? Do you have any idea how deep your plants roots go?

http://www.soilandhealth.org/01aglibrar ... 37toc.html
Every gardener should look at this page.

Thanks for sharing that link ... that looks like some thoughtful and useful information!