The Most Important Four Inches In Your Garden

Reader Contribution by Cam Mather
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I delivered one of my books to a friend in town recently.
She had borrowed “The All You Can Eat Gardening Handbook” from the library but had decided that she wanted her
own copy when she realized that she’d be referring to it throughout the
gardening season. She asked me about getting her garden started this year. She
had removed the grass and was now trying to get the garden ready to plant. She
was hesitant to rent a rototiller because she was afraid she might break it on
some rocks, and I don’t blame her. We live in “Stone Mills Township” and the
one thing that we grow well in our gardens and our fields is stones. And every
year the frost heaves a few new ones up and I manage to hit them with my
rototiller. Luckily I’ve never broken it on a rock.

I asked her what she had done with the layer of sod she had
removed and she pointed to a low spot where she had used it for fill. I
suggested that it would be a good idea to retrieve that sod and put it in the
compost heap. Or just pile it up with the grass facing down and cover it with
old hay to kill the grass but keep the topsoil. Topsoil is really, really
precious, especially in a place like this. When the glaciers retreated eons ago
they left very sandy soil with lots of “big” grains of sand (i.e. stones. Part
of my garden looks a bit like a small gravel pit.

I can’t remember the exact figure but I think I’ve read that
it takes something ridiculous like 50 years to build up an inch of good
topsoil. So if you had trees and they dropped their leaves every year and these
rotted and earthworms chewed them up and pulled them into the soil, it would
take a long time to make a significant amount of soil. So when you remove that
top 2 or three inches of topsoil along with the grass, you’re removing the most
valuable component of your new garden. When I lived in the city there were a
few days each year when yard waste was picked up with the garbage. Some people
would leave big piles of perfectly good sod at the end of their driveways to be
picked up. People in the city have the money to head over to the big box store
to load up on bags of topsoil to replace the topsoil they’ve thrown out. I
don’t.

So save your topsoil at all costs. In my book I talk about
why I am such a big fan of using rotten hay to expand my gardens. If I put it
on thick enough it will kill the grass. I have to leave it a full season for it
to work its magic, but I can usually anticipate where my next garden is going
to go and so I can invest a full season in killing the grass. Hay is great
because it allows water to trickle down through. And it decomposes, so when I’m
ready to till it in the following season, not only have I killed the grass, but
also I’ve added significant organic matter to my soil. I like to think of hay
as “bio-mass”. Some farmer had a big field and this grass grew tall in some
previous summer’s sun. It used photosynthesis to make all this wonderful
grassy, woody biomass. And since an animal didn’t eat it, I’m now going to
incorporate that stored sunshine energy into my soil. I absolutely love it.

The other reason I love using rotten hay is because it
doesn’t disturb all that life in the topsoil that I want to maintain. All those
wonderful microbes and microscopic little creatures that help organic matter to
decompose, or help to free up trapped nutrients and minerals that might be
locked in some of that organic matter, so it’s available for the new crop to
absorb and pass along into this year’s fruit (or vegetable). This is really
important. Again I can’t remember the exact statistics, but some biologists
have suggested that there’s more life by weight in the top couple of inches of
topsoil, than in all the living creatures that live on top of the soil …
humans, cows, elephants, NFL linemen, etc. So when you dig up that topsoil and
get rid of it, you’ve lost all those wonderful microbes that your plants need.

If you want a garden fast and want
to preserve your topsoil you can just dig up the sod and turn it over. The
problem with this method is that it usually doesn’t kill the grass, which will
just turn around, and start growing back towards to the sun.

Instead you might want to try “double digging.” Put on your
work boots and sharpen your shovel and cut the sod in the area where you want
the garden to be into 12″ inch squares, like a checkerboard. Take the first row
of sod that you remove and place it about a foot from where you dug it.

Then
dig out the soil from where the sod was and place it right beside the row.
You’re basically digging a shallow trench where that first row of sod was. Now
when you remove the second row of sod, turn it over grass side down into the
trench you just dug beside it.

Once the row is complete dig another trench
where the sod was and pile that soil on top of the upside-down sod.

By doing
this you’re making sure that the grass and its roots are buried under a deep
enough layer of soil that light will not get down and allow them to live. If
you dig the trench deep enough and pile a deep enough layer of soil on top of
it you’ll be able to grow a garden on top and not have to worry about the sod.

Plus you’ve saved that topsoil even though it’s a little bit
lower than it would otherwise be. If you have healthy soil, earthworms will
help circulate that topsoil back up higher, as will the action of the frost and
other natural processes. I would wait for a year before I used my rototiller or
dug deeply with a shovel to turn the soil over. Make sure the grass is really
dead before you risk bringing it back into the grow zone by accident.

With this process I’d recommend a very deep layer of compost
or composted manure on top because by digging down fairly deep in the trench
you haven’t brought the best soil to the surface. In time these layers will all
get mixed up and you’ll have a wonderful, thick, rich upper layer, but for now
supplement it and make it deep. It wouldn’t be a bad idea to mulch with leaves
or rotten hay to ensure that no light gets through to that lower layer of grass
so you’re sure it’s dead by next season.

Topsoil is precious and you shouldn’t waste it. And if you
see your neighbor with boxes of it out at the curb on garbage day, fire up your
wheelbarrow and get scrounging! There’s gold in those boxes!

For more information about Cam or his books visit www.cammather.com or www.aztext.com