Garden Beds - Sheet Mulch vs Traditional

We recently have been given a green light to put down some vegetable garden beds in the house we are renting. I've been doing lots of reading over the past month on different ways to approach creating garden beds and had plenty of ideas. The two main ones that kept popping up were Sheet Mulch (also known as No Dig) and the Traditional garden beds.

Sheet Mulch beds consist of several layers of different materials that you put down to create what is essentially a very large compost heap. The bed is generally built directly on top of the grass which is smothered by the sheet layer of cardboard or newspaper.

The Traditional garden bed is the one that most of us are familiar with. It usually involves digging up the layer of grass, turning the soil and often importing more soil to fill up the raised garden bed. The soil in the bed is generally turned yearly and a lot of labour goes into digging to make sure the soil is well aerated and fertile.

Matt preparing the traditional garden bed

Because we are initially doing two garden beds I decided to do one of each to see how they compare. Both beds will be raised garden beds built from untreated Australian hardwood. They measure 2.4m x 4.8m which will give us roughly 11.5 square meters per bed. According to some of the books I have read 10 square meters is enough to provide all the greens and vegetables for one person over the course of one year. So a total of 23 square meters should feed my wife, our soon to arrive baby and myself .

Below is the procedure I used to make the two different garden beds.

TRADITIONAL GARDEN BED
1. Lay out the timber to position the garden bed and assembled the bed.

• Make sure the long sides of your beds face north/south to get maximum sun exposure
• Position the bed somewhere it will get at least 6-8 hours of full sun in winter and summer.
• Place it close to the house so it is easy to get to or else it will get neglected.

2. Prepare ground beneath the bed.

Forking the Soil/Grass

• Dig up the layer of grass and weeds. I skipped this step because I am going to use 1 layer of cardboard to suffocate them. This will save me time and save my lower back (I'm getting old).
• Generally you would double dig (refer to article here) the soil if you weren't doing a raised garden bed. Because I was raising my garden bed and importing soil I didn't double dig but I did use a garden fork to put holes into the ground. This improves the soils ability to hold air and water.
• Add any soil amendments. I put down a layer of gypsum and blood and bone. The Gypsum will help soften the bottom layer of soil and the blood and bone will help activate the worms and microbes.
• Water the bottom layer well.

3. Fill raised garden bed with soil.

• Make sure you select a good weed free soil that will drain well. I went to a local nursery and purchase a premium sandy loam that had several rotted manures and blood and bone added to it.

4. Water the bed, plant and mulch

• Make sure you get the bed a good soaking before you plant out and mulch the bed.
• I will be using a 50-70 mm layer of sugar cane mulch. Other options are lucerne and straw but make sure you get seed free or else you will be growing more weeds and straw than actual veges.

The completed Traditional garden bed.

SHEET MULCH BED

1. Lay out the timber to position the garden bed and assembled the bed.

Manure Layer

• This is the same as the Traditional garden bed.

2.  Put down a manure/nitrogen layer (optional)

• I put down a layer of horse manure on top of the grass to attract worms and microbes up into my bed. This is placed directly on top of the weeds and grass.
• Water the ground and manure well.

3. Put down a sheet (cardboard/newspaper) layer.

Cardboard Layer

• Lay newspaper or cardboard on top of the manure and grass. Make sure you don't use glossy pages and remove all plastic and staples.
• Don't leave any gaps or else the weeds/grass can grow up through your bed.
• Use about 4-6 layers of newspaper or 1 layer of cardboard.
• Water the layer well.

4. Put down a nitrogen layer.

Grass Clippings

• I put down a small amount of manure and a 50 mm layer of fresh grass clippings.
• Water down well.

5. Put down a carbon layer.

• On top of the grass and manure I put down a 50 mm layer of sugar cane mulch. You could use shredded paper, dry brown leaves ...etc.
• Water down well.

Unbroken down Compost

6. Put down a nitrogen layer

• Next I lay down a thick layer of semi broken down compost.This will help introduce lots of worms and microbes to the garden. You could use kitchen scraps.
• Water down well.

7. Put down a carbon layer.

• This is the same as step 5. 

8. Put down a layer of soil (optional).

Sugar Cane Mulch Layer

• Because I wanted to plant the garden out in the next few weeks I put down a 20-30 mm layer of soil.
• Water down well.

9. Put down a mulch layer.

• Lastly I lay down a 70 mm thick layer of sugar cane mulch. As discussed in the traditional gardens mulch layer you can use other things like lucerne or straw but try and get seed free mulches.
• Water down well.



Adding the Mulch Layer

• If you didn't add a soil layer and want to plant out simply pull the mulch apart to form a hole and fill with a little bit of soil. Then you can plant your seedlings or seeds into that soil.

Important Notes on the Sheet Mulch bed

The whole idea of this bed is to create your own rich soil by combining the nitrogen and carbon layers together. The different components will be broken down by worms, microbes, fungi ...etc which in turns creates a very rich soil. Because this process can take some time the beds won't reach their maximum performance for 2-3 years. But as time progress you should see things accelerate fairly quickly.

What are we trying to achieve

These days self sufficiency means a lot of things and I think there are many different areas and levels of self sufficiency. For example you could be self sufficient in terms of your water and waste by using a tank and onsite septic system. I think at the outset of our journey it is important to break our journey into steps and define our initial goal for "Self Sufficiency".

Our short term goal is to grow and live off most of our own vegetables, salad greens and herbs. We hope to only have to buy veges, salad greens and herbs that won't grow in our climate/garden. This will mean that our garden will feed us (Hester, Myself and our baby-to-be) and that we will feed our garden using resources from our garden (chook poo, kitchen scraps, lawn clippings, prunings, spent plants ... etc).

In order to achieve our goal we will be using many different ideas from "Organic Gardening" and "Permaculture". I hope that this journal/blog will be a place for people to get ideas and see that eating fresh and healthy food is achievable  even for the every day person. I am hopeful that we will reach our goal so keep an eye on our progress and if give some of the ideas a go yourself.

Our heirloom lettuces from a spring harvest