Too much compost in the garden a bad thing?

bigrich(5)July 20, 2010


I am planning for next year early and looking forward to building several raised beds for my garden. I currently have a traditional row garden in a space of about 15'x25' and think I could do better with raised beds i.e. yield vs. space. I figure I will need about 300cu foot of dirt to fill the beds I want to use at the height I want. I'm currently composting a 4x4 pallet space and making good progress, just not enough to help out my raised beds at this pace. I have access to as much "brown" compost I want in the form of dead leaves that my city collects and turns into compost for all that want to buy. My question is can I amend/add/till 300 or so cu. feet of that to my current soil in the fall(zone 5) let it sit all winter and have it nice and usable for the spring/end of May planting. Or does that have the potential to ruin the soil for a year? Is it too much of a good thing?

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You would probably need to shred those leaves and add some lime to get it all to break down. If you turned that many in whole I think you might find them still undigested in the Spring.

    Bookmark   July 20, 2010 at 12:00PM
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toxcrusadr(Zone 6a - MO)

I am not clear whether you are getting uncomposted leaves, or compost made from them. It sounds more like you would be adding shredded leaves this fall. Adding 300 cu ft. of leaves over 375 sq ft of area is about 10 inches of shredded leaves. I would be a bit concerned about that being ready for spring.

Not sure if lime is going to speed that up, what you need is some greens.

Another alternative is to let the leaves be a mulch. Bring in your new soil first, lay that down, add the leaves but do not till in. In spring, plant through the undigested leaf layer into the good stuff underneath. That is, with tomatoes, peppers etc. The leaves will continue to break down on the surface and will not rob nitrogen. Might not work so great with small seeds though.

Me, I'd get some greens and make it a huge sheet composting operation. By spring it would be ready to dig/till in.

    Bookmark   July 20, 2010 at 1:30PM
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I think that would depend on how much composting takes place over the Winter. If your pile freezes it will be very little. As noted by other posters some greens would be a big help. Also don't forget "magical golden elixir" Pee in common terms. It does wonders for a low nitrogen compost heap. Just pour it on top and it will work its way down. Tarp if odor is a problem where your pile is. The more you can turn the pile the better. Leaves are notorious for compacting too much. It isn't likely you'll get much heat out of a compost pile made mostly of leaves but there is nothing wrong with cold composting except that it's slower.

    Bookmark   July 20, 2010 at 2:01PM
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Sorry, it would be good black soil of mostly composted leaves. The city collects all the leaves from the residences in the fall and has a rather large area devoted to composting those leaves. It then sells/uses the compost. I would be putting "mostly" composted dead leaves in the garden. i.e. BLACK soil.

I just drove past the place and it is REALLY black soil. My thoughts would be that it'd be great for growing. But I'm new to the whole composting business.

Reading the forums and some articles on the subject leads me to believe that compost of only one thing doesn't make good soil. That's my concern. Will adding so much carbon rich compost to the garden be ok? It will weather for at least 6-7 months before the new plants go in next year.

I apologize for being unclear in my previous post.

    Bookmark   July 20, 2010 at 2:04PM
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I would wet the soil of the garden space, spread the leaves evenly over it, wet the leaves and try keeping them as watered as reasonably possible. The damp leaves combined with moist soil underneath tends to draw up worms. Worms LOVE munching on damp leaves. Also fungus will start to kick in to assist. You have plenty of time until next spring for nature's little composters to break down those leaves. It'll make an excellent weed block too. You're gonna have some pretty decent soil after this! :)

    Bookmark   July 20, 2010 at 2:53PM
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If it's all black and when you pick up a handfull you don't see any leaves that aren't broken down, or at least in the process of it I say go for it. Your chances of picking up harmfull chemicals from composted leaves are far less than from lawn clippings. Get your beds mixed and filled as soon as possible so the microbes in the soil and the compost "get to know" one another. By Spring you should have a fabulous garden bed. The only problem you might have is acid if there are a lot of oak trees in your area but that's easily countered with a little lime (cheap). To answer your original question there is no such thing as too much compost. I've grown great pumpkins and squash right in a compost pile.

    Bookmark   July 20, 2010 at 3:50PM
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Alright! Great. Thanks for the replies.

    Bookmark   July 20, 2010 at 4:08PM
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chinamigarden(z5 MI)

Remember that if you need/want your beds to be a certain height, adding 10" of compost now will not be 10" tall in the spring. I would go half and half top soil and compost if it were me.

    Bookmark   July 22, 2010 at 7:02PM
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My technique for making new vegetable garden beds has evolved to this;

I'm working from a lawn with some pretty healthy grass growing, so I start by digging up chunks of the sod and scalping the sod from the clay soil with a machete. That leaves me with clay soil in large chunks. Once I've cleared enough area, I clear off the chunks of clay soil from one end and loosen the subsoil with a broadfork. I am careful not to turn the subsoil, just loosen it.

I'll toss some humic acid on the top of the subsoil as I work across the bed. When the subsoil have been loosened, and the clay chunks are sitting on top, I'll level the surface as best I can. That's when I start to amend the soil.

I use humic acid and organic lawn food and mix that into the top 2" of soil. Then I'll put on 3-4" finished compost, then 3" unfinished compost, then a mulch. Lately I've been using wheat straw covered with fresh grass clippings.

I did this last fall to extend an existing garden bed. The soil looks terrific and the tomato plants look great this year. I'll add some of my home made compost and/or bulk compost from the nursery this fall.

    Bookmark   July 22, 2010 at 7:30PM
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It can take 3 to 5 years after adding suffiecient quantities of organic matter to soil to see good results because it can take the Soil Food Web that long to develop, especially in a soil that had no such thing. What soil needs is organic matter and compost is part of the organic matter you can add to soil, but compost does not need to be the only type of organic matter.
You want in the neighborhood of 5 to 8 percent humus, the residual organic matter, in your soil. You can get too much organic matter in soils, bogs and swamps come to mind right off.

    Bookmark   July 23, 2010 at 7:43AM
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wayne_5 zone 6a Central Indiana

I have used simular black leaf compost. It makes a wonderful addition, but 10 inches at once? I think that I would want to mix it in with the topsoil somewhat.

    Bookmark   July 24, 2010 at 2:19PM
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nancyjane_gardener(Zone 8ish North of San Francisco in the "real" wine country)

Do you have a starbucks or other coffee place near by? I was getting 2-3 gal of UCGs a day from a store nearby! And that was just from a couple of hours in the morning! I could have had 5 gal or more of the coffee grounds if I came in later in the day! They mixed great with all the leaves I had.
You can also check with local gardeners if the grass they are cutting is treated with any chemicals. They often use the mulching mowers, but I have come across some that will even load the clippings into your bag for you! Hope this helps. Nancy

    Bookmark   July 24, 2010 at 10:50PM
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oregonwoodsmoke(5 OR Sunset 1A)

Here's how I made my raised beds. They are 24 inches tall, walled in cedar boards.

On the bottom, hardware cloth which drains and keeps the 4 legged diggers out. Plastic sheeting lining the walls to keep the water from running out between the boards.

Then a layer of dirt in the bottom, spread out, top with a layer of stable manure. Then I get in there with a shovel and turn it together. Then repeat the layers and mix.

As I get higher in the bed, I stop with the manure and add compost. Layer and mix. About 2/3 dirt, 1/3 compost.

You will find that as time goes by, the organics get smaller and your soil level will drop, so don't plant long term plants the first year or so (like asparagus) because you are going to want to add more soil to the top as years go along.

I made similar raised beds several years ago, walled in cinder block and filled with layers of sand and compost, mixed together. Soil level has dropped about 6 inches, but stuff grows well in them.

Get as much compost as you can get your hands on. You'll find a use for the stuff you don't build the beds with.

    Bookmark   July 29, 2010 at 4:38PM
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beachlakegrower(5b PA)

I put in 10-inch raised beds to do gardening with kids at a summer day camp. The community that sponsors the camp provided compost to fill the beds. The compost is from leaves, etc. that the community's maintenance crew collects.

It's very nice compost, but by itself I found it is not the optimal growing medium for the veggies I've grown with the kids, because It dries out too quickly.

From what I understand,compost should be treated as a soil amendment and not as a substitute for soil. It provides drainage to poorly drained soils and helps overly porous soils hold more moisture.

Next year, I will definitely be adding some soil to the raised beds to enhance their moisture holding capacity.

    Bookmark   July 29, 2010 at 7:56PM
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