Homegrown: Garden bed soil
I am getting a delivery of Glade Park soil for raised vegetable garden beds constructed of 20- to 24-inch high concrete blocks. The contractor says that in filling the beds he needs to walk on the Glade Park soil to compact it because it is so fluffy. I thought that you are not supposed to compact garden bed soil. Should I, instead, tamp it slightly or let it settle or water it in and add more compost in the spring? Should I cover the natural soil base and line the bed sides with landscape cloth?
Thanks for your time and expertise.
Actually, I agree up to a point with your contractor.
When a new bed is filled, the soil is quite fluffy. As time goes by and gravity and watering do their thing, that fluffy soil will settle quite a bit, requiring the addition of more soil.
When I’ve filled beds in my yard, I’ve walked on the soil to compact it down a bit. Having said that, there is a point where you can compact the soil too much.
Your concern about compaction is right on.
When I walk on the soil. I’m not jumping up and down. I’m walking gently, letting my weight do the work. I’m not stomping.
Some folks are uncomfortable doing even this, and they’ll settle the soil by watering it thoroughly and letting it drain. This will certainly do the trick, though it may take a couple good soakings to get it completely settled down.
The problem I have with doing it this way is the time involved. I have to water the bed, let it soak in completely, and then add more soil as needed. Water again, wait, and add soil again. And maybe water again, wait, and add soil yet again.
Doing it this way can take a week or more. Gently firming it with my boots accomplishes the job quickly, so I know I have the right amount of soil in the bed to bring it up to the grade I want.
I’ve never had problems with plants growing in an area like that. There’s still plenty of pore space for the roots to grow. I like lining the sides of the bed with landscape cloth. It allows for the exchange of water and oxygen that is good for plant growth but prevents the soil from filtering out of the cracks and seams.
We usually don’t put it on the natural soil base. I like to make a transition zone where I mix a couple inches of the new soil mix with the native soil before filling the rest of the bed with the straight soil mix. This facilitates water drainage out of the new bed.
The only times I’ll line the bottom with landscape cloth is if there are high salts in the native soil and you need to isolate the new soil mix from the salty junk.
The way we’ll do that is to put down 3 or 4 inches of washed gravel on top of the native soil, then the landscape fabric on top of it to act as a filter cloth to prevent the soil mix from settling down into the gravel.
The other time I might put the fabric down is if there is a problem with a tenacious perennial weed such as bindweed or Bermuda grass.
The fabric isn’t perfect for this but should prevent most all of it from coming through.