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Lightening up the soil?

Posted by bart1 6/7 Northern VA (My Page) on
Tue, Apr 6, 10 at 9:05

I think I know the answer to this question, but I'll ask it anyway......What's the best way to lighten up garden soil?

I have a raised bed that I put in years ago. It's made up of 4"x4s" so it's not too high, but over the years it has seemed to sink a little bit. I made the bed by laying newspaper over the ground/grass and filling it with pine bark mulch and composted manure. It's in a low part of the yard where water often pools during heavy rains and seems to take forever to dry out. For instance, most of my yard is rock hard and dry right now, but the raised bed is still "wet" (not really wet, but moist and very thick - not crumbly at all). I just added another 4x4 to raise the soil level and get the plant zone out of the muck/water zone.

I'd like to make the soil lighter, "thinner" and with more drainage. I know the best thing is to add compost which I have and will add, but I'm wondering if I should add anything else like pearlite, vermiculate, or sand? Or should I just stick to compost and shreaded leaves?


Follow-Up Postings:

RE: Lightening up the soil?

Sand works - but there isn't much value in sand. I would recommend staying with the compost myself - never hurts to put nutrients and organic matter into the mix.

If you need to loosen the soil up a bit, you may look into getting one of those claw tools - put it into the soil and twist and it loosens up the soil. I use one for the raised beds and am pleased with it - although it is a lot of work with the larger beds!

Here is a link that might be useful: BsnTech Gardening Blog

RE: Lightening up the soil?

Sounds like you are going to have to either dig down through the clay layer (maybe 2 ft until you hit get below that layer) to allow water to drain down faster or actually put in drainage lines, either horizontal to a lower place or deep gravel filled holes (post hole digger or auger) I think that there was a discussion over in the soil forum recently about tecniques.

Most soil has A, B and C horizons, A is topsoil, B is where clay seeping down from above tends to settle out into a thick layer, and C which is often more sandy and better draining. House construction activity makes the clay layer worse before they put down the new lawn. sometimes this can be only 6-10 inches deep, other times much thicker, but you usually stil have to dig through 6-10 inches of topsoil before you get to it, so you end up with a pretty serious digging job.

To drain our yard and keep water out of the basement we had a backhoe come in and dig a trench the length of our yard down from the low spot, ending at the lowest spot at the edge of the property. The trench was filled with gravel and then covered. They should have put in a drainage pipe at the low end because the clay and soil eventually plugged up the end of the trench and stopped drainage. I had to dig out the end and put a short section of 4" pipe in to let the water out. We still get a pond out back during heavy rains but it drains away in 24 hours.

RE: Lightening up the soil?

  • Posted by bart1 6/7 Northern VA (My Page) on
    Wed, Apr 7, 10 at 8:05

Thanks folks!

RE: Lightening up the soil?

bart1 -

I think I'm having a similar problem with a few of my boxes too. So - my strategy is -

The dirt in the box is worn out - after 5-10 years or so. Recently, I had to take up one of them because I'd forgotten to put hardware cloth on the bottom when I placed it, and a vole came up underneath, ruining the plants in it.

Well - long story short - I replaced the box, added a lot of rough compost and new cardboard in the bottom, put SOME of the old dirt back, then added lots of new sifted compost, and bone meal to fill back up. Sooo - my thinking is - from time to time now, I will refresh and replace the old dirt with quite a lot of new compost added.

You should see the cabbages that I planted in that refurbished box - they are huge. I plan to treat some of the older boxes that way - starting a few at a time, as they empty.

Also - one old reminder, if you can wad up the dirt in your hand to form a ball, it is too wet to plant in. If you do, the soil will pack hard as it warms and dries out, suffocating the roots from lack of air.

Just my 2 c's.


RE: Lightening up the soil?

I've done quite a few raised beds which have very nice loose and spongy soil.
I have added to the existing top soil about 4 or 5 inches of sand; about 4 inches of spaghnum peat moss from a local bog; and lots of mulched and composted leaves plus lots of horse manure...all mixed in deeply with the topsoil......wonderful.

RE: Lightening up the soil?

Beds need some clay, some sand, and a good amount of organic matter. All of anything isn't ideal.

If the soil in your bed is hard, it might be low in calcium (high rainfall or excessive watering can wash it away).

Before you add anything to one or two of the existing beds that you are anticipating renovating, you might collect some of the soil in them and take/send them in to a soil lab (usually only about $10) and get some idea where you need to go. Additional calcium helps the soil to drain, magnesium will tighten it up. Without the test, you won't know which way to jump.

Your local Cooperative Extension/Master Gardener can give suggestions on labs. If you do organic, BE SURE to note on your request that you do garden organically, as they tend to automatically lean toward chemical farming if no specification is made.


Here is a link that might be useful: Find your Coop. Ext. Service

RE: Lightening up the soil?

g'day bart,

our medium in our raised beds nice and light created from spent mushroom compost from the farm, did top up a few bags of mushy at one stage would like to do it again maybe one day. trouble is we only have 16sq/mts of garden so it is fully planted in both seasons, so currently relying on the mulching and addition of food scraps daily to keep height up. have added some grass clip along the way. all spent plants get mulched back in where they once grew.

now 4 years old so the beds seem more stable now that is not dissapearing into the ground we started with about 12"s high and still got at least 10"s to 12"s.

the medium must be good as this seasons plantings of brassicas all kicked off nicely looking healthy and with good growth. the medium looks and feels good full of worms and all the necessary structure.


Here is a link that might be useful: lens garden page

RE: Lightening up the soil?

For drainage, you could add an inch or two of gravel at the bottoms of your beds and add some red wiggler worms to them as well.

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