Unfinished compost at the floor of new raised garden bed

2 years ago

I just built a raised garden bed a few weeks ago and started composting immediately. It's started to really break down, but I have about 3 weeks before I need to start planting!

My plan was to basically have the floor of the raised garden bed be compost so that I could fill up the box a bit without spending as much money on soil. I'll have about 16 inches of raised garden mix on the top, but I don't know whether or not it's a good idea to put soil on top of unfinished compost. Do you think there's any harm in it given that there will be so much fresh raised garden mix on top of it?

Featured Answer

klem1

2 years ago

Covering unfinished compost with rich soil will be fine. I've been building mounds and raised beds with uncomposted material at bottom for years. I typically lay 2"to 4"(depending on size of bed/mound) limbs/logs on ground followed by smaller limbs, leaves,twigs,wood chips and hay mixed with and topped with cow or horse manure. Well amended soil covering will support annuals 1st year then increasingly deeper rooted plants each year. Soil level drop's as material decays so I mix native soil with top layer in raised beds each year. I add nothing other than fertilizer and castings to mounds as they drop in height. After 8-12 years,soil around shrubs,fruit and shade trees planted on two foot, 3 year old mounds is 3-6 inches higher than grade. You might ask why i include large uncomposted material. (A) it save's ground space (B) soil constantly moving as material decay's alow's air penitration (C) far less water is required after 1st year (D) it alows using material that a home chipper can't handle.

OP,we would love hearing how this work's out for you.

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Comments (6)

JoJo (Nevada 9A)
2 years ago
last modified: 2 years ago
I have some experience trench-composting in my veg beds (burying garden and kitchen waste between rows) with good results. So burying unfinished compost won't hurt your beds.

The only (slight) drawback I can think of -- after the compost is finished decomposing, the soil level in your beds will drop.
Sam Ellis thanked JoJo (Nevada 9A)
Nevermore44 - 6a
2 years ago
With 16 ” of material on top…. you could bury anything you want. For raised beds, i run into people that also fill them with soilless media who then have the problem of the bed drying out too quickly and they bed needing continual fertilization. so keep an eye on both.

i advise folks to dig down into their native soil some (if it had clay and not just pure sand sand) and mix it with the new media.
Sam Ellis thanked Nevermore44 - 6a
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Sam Ellis
Original Author
2 years ago
Thanks all! given that I've got a whole lot of creepy crawlers and fungi growing in the compost pile right now, is there any risk that those things will be bad for the soil that will be going on top? Or is that all part of the process and safe for the most part?
gardengal48 (PNW Z8/9)
2 years ago
"Or is that all part of the process and safe for the most part?

Yes :-) There is very little risk to anything when using a mixed ingredient compost, even an unfinished one. There may be some nutrient unavailability with not fully 'finished' compost but nothing to get concerned about and at 16 inches deep, is pretty much a moot point in this case.

Layering different types of soil textures (rather than incorporating all together) will impact drainage as the layering slows percolation but again not a big concern here
Richard Brennan
2 years ago
"given that I've got a whole lot of creepy crawlers and fungi growing in the compost pile right now, is there any risk that those things will be bad for the soil that will be going on top?"

Nope - that's nature at work. It's not the best environment for seedlings (which is why mulch discourages weed seeds from sprouting), but it is fine for the soil.

I also agree with Nevermore44, one of the best soil prep methods for raised beds is to add your amendments, and then dig down a foot or so into the base soil and turn it all in. That alone will raise the soil level about 5 or 6 inches as it brings air pockets back into earth and distributes your organic matter throughout the bed.

Unfinished compost at the floor of new raised garden bed

klem1

Comments (6)

JoJo (Nevada 9A)

Nevermore44 - 6a

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Unfinished compost at the floor of new raised garden bed

klem1

Comments (6)

JoJo (Nevada 9A)

Nevermore44 - 6a

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Sam EllisOriginal Author

gardengal48 (PNW Z8/9)

Richard Brennan

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Sam Ellis
Original Author