Sustainable NE Seattle

Connecting for a sustainable community

There’s a running debate on how to best transition an old lawn into a productive, sustainable patch of earth.  Regardless of the method, there are many good reasons to make the change and a good variety of landscape planting designs that would contribute to an improved planet by sequestering carbon and lowering carbon emissions, feeding the animals and people while providing beauty and a sense of purpose.  Whether the purpose is to grow a kitchen garden, plant natives for wildlife, cultivate endangered species for genetic diversity, or combine all these objectives into an edible forest, it all begins in the dirt.

Nothing seems more lifeless to me than a compacted Seattle lawn.  After years of traipsing back and forth pushing the lawn mower and countless hours of walking, playing or whatever on our lawns, they have become biological deserts with a density approximating concrete.  By comparison healthy soil is teeming with life and when you have to walk upon it you can feel yourself settle into the ground.  This soil is alive with bacteria, fungi & critters, it’s full of air and comprised beautiful crumbs, you can practically reach down into the soil with your bare hands when the it’s healthy.  But how do you get there?

Sheet Mulching.  Perhaps the first commandment of Permaculture, sheet mulching is simple and effective.  First it helps to understand a little about decomposition, which is all about carbon and nitrogen.  If the ratio is right, about 10 to 1, then the biological processes will occur and decomposition takes place.  So the first step in sheet mulching is to provide the carbon build-up in the lawn with enough nitrogen to hasten the process.  Even if you cut away the sod there are still a lot of roots in the soil, either way add an organic source of nitrogen like Blood Meal and top it with a thin layer of Compost to feed the critters before laying out that Cardboard.  And be sure to wet down the cardboard to start its decomposition as well.  If you’re working on a slope get some stakes, from tree limbs for example and pin the cardboard down.  Use bigger straight branches placed across the slope behind the stakes to keep the mulch from sliding off.  It all rots away with time.

Once you have wet cardboard in place it’s time to build your sheet mulch pizza.  Any organic matter you like can be used, but remember the bigger woody pieces will take longer to breakdown.  I like to use compost, leaves, arborist chips, sawdust (not too much), and other small clippings.  Make the final layer the arborist chips and you won’t find all your leaves scattered after a windy day.  Then wait.

It’ll take maybe a year for the grass to die, maybe more.  And if you get ants in your pants and dig in there too soon you may breathe life back into those weedy grasses.  They could then haunt you for years to come, or…

you can give the Sodbuster method a try.

One of the beauties of traditional sheet mulching is that you can apply it to small areas and do it around existing plants.  Sodbusting isn’t like that; it works best on large areas of lawn.  The benefit is that you achieve a plantable condition much sooner.  No, it doesn’t promise you that there won’t be weeds but you won’t have those big clumps of grass roots.  Sheet mulching is a part of the process and you can do it in fall or spring.  Leave the site covered over winter or summer, then you can plant the next spring or fall.

Here’s the process:  cut away the sod using a sodcutter.  They can be rented but you’ll need a truck and ramps to move it about.*  Pick up the sod and pile it in a berm maybe two-feet high.  I like to choose a location where I want to plant a tree.  Cover the pile with 12 inches of arborist chips.  Seriously, put it on thick, you have to smother those roots to death!  Leave the site alone for two-years, seriously, just ignore that area and get back to work on the real immediate problem of that bald patch you’ve just created.  The next step is real work.  Remember that this is a once in a garden-lifetime process.  I always try to think that it’s just from here to there, take it one step at a time and never give-up and you’ll get it done.  It’s time to undo years of compaction by turning the soil.

Turn the soil with a standard shovel.  Don’t try to pick-up too big a piece in one bite, the objective is to loosen the soil as deep as possible and create a three-dimensional surface.  I like to turn the soil going back and forth until I have a band about four feet wide.  Then, without stepping into the area, sprinkle my soil amendment mixture and tip some compost over that, spreading it about two-inches deep at least.  My soil amendment mixture is mostly aimed at providing micro nutrients and phosphorus.  Phosphorus is the primary “missing ingredient” in our PNW soils.  Of course nitrogen is always in demand, but because of it’s ephemeral nature we’ll only use a small amount to promote decomposition.

Rock Phosphate, 0-3-0,  10 pounds per 100 sq ft, source of phosphorus, trace minerals, calcium.  Phosphorus is not water soluble and is hard to work into the soil, but it also doesn’t leach out.

Kelp Meal, 1-.01-2,  5 pounds per 100 sq ft, source of potash, trace minerals, amino acids and natural plant hormones.

Greensand, 0-0-3,  1 pound per 100 sq ft, source of iron-potash-silicates, promotes water conservation.

Blood Meal, 12-0-0,  1 pound per 100 sq ft, source of nitrogen, promotes decompostion of carbon build-up in the soil.

Next you can begin to spread the organic materials just the same as in the standard sheet mulch pizza:  leaves, clippings, arborist chips, or whatever.  What you want to avoid is cardboard, because in six months you are going to rototill the site.  This may cause some wood chips to be turned into the soil, so add nitrogen to compensate.  We all have a “number one” source of nitrogen and it’s no joke.  I’ll admit that I have a special collection canister and special watering can, in which I dilute my pee with water (10:1) and sprinkle it about.  This can be done anytime and is a great source of cheap fertilizer that works!  Works good on the compost pile, too.  Leaves are the best because they will breakdown faster.

Once the garden soil is tilled it’s time to create pathways.  Staying off the planting beds is critical to good gardening, so make the beds narrow enough to match your reach.  Install large stepping stones in shrub beds, places to stand when you need access.  For the paths, make them wide enough to allow passage easily.  Take the improved soil out of the paths and place it atop the planting beds which will then be raised well above the pathway trenches.  Fill the pathways with arborist chips, cedar play chips, or crushed rock, depending on your style.  Top with burlap bags, pea gravel or bricks.

So why do I prefer this method over regular sheet mulching?  1) Speeds up the time required between wanting a garden and having a garden.  2) Loosens up compacted soil.  3) Works soil amendments deeper into the soil profile.  4) Conserves topsoil by moving improved soil into the planting beds and replaces pathways with appropriate materials suitable to the gardener’s taste.  5) Greatly reduces the recurrence of weeds.  6) Creates excellent topsoil when the sod pile is finally dead and the arborist chips have decayed.

* Join the SusNE Urban Farmers for a Sodbusters Saturday.  We’ll provide the truck and rent the tool, sharing the expense, and your community friends will have it stripped in a day!  (testimonials please)

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