Sodbusting Saturdays is one way to quickly convert an unwanted patch of lawn into a productive garden. What you grow as an alternative to lawn is your choice; anything would be an improvement over grass. You might be considering this as a way to add more native plantings or start a vegetable garden. Either planting option will be a great improvement for the environment.
While it is true that you don't have to cut and remove the sod to successfully convert lawn to planting beds, there are a few advantages, especially if the goal is food gardening. A few of the reasons for eliminating grasses include: persistent weedy roots are greatly reduced which improves the chances that the sheet mulching will be successful; sod is slow to decompose, demands a lot of nitrogen to balance the carbon, and may form an undesirable soil interface; sheet mulching over sod may require waiting a year or more before planting some vegetable gardens because it will take that long to insure the weeds are gone. Frankly, while this may be only an aesthetic judgment, I've seen too many gardens infested with weedy grasses, which hog up on all the soil nutrients, suppress desirable plantings and take time to weed out, and for that reason alone, I recommend attacking with gusto!
Some of the advantages of removing the sod include: major reduction in the actively growing part of the grass plants, thus reducing the amount of weeding (don't think for a moment that sheet mulching eliminates weeding); offers the opportunity to turn the soil with a shovel to loosen the compaction caused by years of foot traffic; makes it possible to plant a vegetable garden almost immediately. Just by the way, the photograph that accompanies the Sodbusters Event posting is Jessie's garden just days after sod removal (more about how it was developed follows).
So, the first decision to make after you've decided to use a sodcutter is how much to remove. I recommend making the shape and scale as simple as possible. Do not keep grass paths, but instead have well defined boundaries. If you have an edge that is shared with a lawn, especially one of our old Seattle weedy lawns, then you might want to install a physical barrier. In Jessie's garden we used old scraps of plywood, placed vertically in a trench along the edge of the lawn.
The next step is join us on a Sodbusting Saturday, where we'll rent the sodcutter and tour a few gardens, cutting and removing the sod. Sometimes I haul the sod to Pacific Topsoils and let them compost the sod for me, but a good alternative is to keep this resource in your garden. What I recommend is choose a location where you might want to plant a tree, then pile the sod in a gently sloping pile and sheet mulch the heck out of it! You'll want to leave it alone for at least two years, just to make sure the grass is dead. But there are some ways to plant sooner. Remember that decomposing plant materials uses nitrogen to breakdown the carbon, so if you want to plant, be sure to fertilize regularly with an organic nitrogen fertilizer. What you can do with the sod pile is create planting pockets, using imported topsoil to establish root space. As the sod decomposes it will create wonderful topsoil to nourish your new trees. You can sheet mulch the pile in the usual fashion (described below), but be sure to top it with a thick layer of arborist chips. You don't need to use cardboard if the chips are six-inches or more, and never cover the pile with a waterproof barrier like plastic, it is just a bad idea.
After the sod is off, piled and sheet mulched, it's time to address the newly created bare patch of earth. I like to turn the soil by cutting it deeply with a shovel, attempting to expose as much of the lower soil as possible. Don't break the soil up, but instead leave it as coarse as possible, before dressing the soil with organic soil amendments. The purpose of these amendments is to introduce micro nutrients, as well as phosphorus and potassium (elements P & K). My blend includes Rock Phosphate @ 10# per 100sf, Greensand @ 5# per 100sf, and Kelp Meal @ 1# per 100sf. Mix these up in a wheel barrow and spread evenly over the site. Next you might want to add a source of nitrogen (N) if there still is a lot of carbon, like roots, in the soil.
At Jessie's garden, after spreading the blended micro nutrients, we spread compost (about 2-4 inches) then rototilled the site. The photo shows the garden after the freshly rototilled soil has been graded into ridges and valleys. We did this to create paths, where the improved soil is removed from the pathway and placed on the planting spaces. This raises the planting bed, improving the depth of good soil. The sunken pathway is then filled with arborist chips to raise its level, prevent weeds, and create a mud-free area to work from. This garden was quite productive in its first year of cultivation, even after a Spring sodbusting.
Sheet mulching usually follows sod removal when it is done in the Fall. And these instructions are applicable also to sheet mulching when the sod is not cut. Manure is a great first first layer when sheet mulching. Its nitrogen content helps balance the carbon and thus speeds the decomposition. Compost is also effective as a first layer if manure is in short supply. Both of these should be applied before putting down the cardboard layer. The bigger the sheets the better, and wet them down if you can before hand. Use steel pins or wood stakes when sheet mulching slopes to insure they don't slide away. After the cardboard is down, just about any kind of organic material is okay in creating a multi-layered pile: leaves, old compost, arborist chips. It all works, but think about the wind and put weightier material on top to keep the mulch in place. The burlap bags available from coffee roasters works exceptionally well to create that extra special environment as the soil biota returns to your garden soil, and keep the wind from blowing away all your hard work.
Now if this were traditional sheet mulching, you would cut holes in the layers of mulch, including the cardboard, and plant. This works well with trees and shrubs, plants that have single stems and cast a large shadow. You'll want to introduce herbs, groundcovers and perennials later, once the weeds are dead. If you've chosen to remove the sod and loosened the soil, then sheet mulched with compost, cardboard, and leaves, by next Spring you'll be able to turn patches of your new garden and begin planting. I recommend that you still take it slowly, focusing on crops that grow from single stems, like squash, beans, peas, tomatoes. You'll need to monitor the garden closely to eliminate any weeds that may have survived, and that's more easily accomplished if you don't plant ground crops, like potatoes or carrots.
I know this is a lot to take in, but sheet mulching is the key to converting unwanted lawns into productive gardens. With luck you'll be eating the sweet rewards!