BUILDING BEDS WITH THE DEEP COMPOST MULCH SYSTEM

After exploring what the deep compost mulch system is, looking at the pros and cons, and how to source your compost, it’s time to get into the details of building deep compost beds from start to finish. The ideal progression of steps is as follows:

Though minimal disturbance of the soil is central to the no-till methodology, in most situations it’s unavoidable when first turning bare ground into cultivated growing space. Some plots may already have an evenly graded slope and good drainage, but in reality, most will need some work to get there. This could require some earth moving, grading, and an initial till. This is definitely a step you don’t want to repeat later due to poor planning or cutting corners. Then it’s back to zero building up the life in your soil. Even if a pasture looks really even, there are likely low spots and high spots that will cause certain sections to flood in heavy rains. Do what’s necessary at the beginning to avoid any chance of your beds flooding or getting washed out by extreme weather events.

Once your site is leveled (with at least a slight slope for drainage) and you’ve figured out the orientation of your beds for ideal drain sufficiently, it’s time to test your soil and amend it as needed. While the deep mulch compost system won’t be completely reliant on the native soil (with such a nutrient-dense, deep layer of compost), you still want to address any imbalances for the long-term health of your growing space. 

While soil testing is highly informative, remember that it’s just one tool in a multifaceted approach to creating healthy, balanced, biologically diverse soil. It’s also important to remember that a soil sample is only one snapshot of a specific place on your farm at a specific time. Getting multiple samples from multiple areas will give you the best overall window into your soil needs. If you want to go more in-depth on soil testing and analysis, consider working with a professional agronomist. 

The next step is killing off any existing vegetation in the grow space by covering it up with silage tarps. Silage tarps are an amazing tool for the small-scale farmer. Having some on hand at your farm is highly recommended. They are reversible, with black on one side and white on the other, which can be used for different applications. The black side up is typically used for the killing of the vegetation, as it amplifies the heat.

The beauty of the tarp system is that it saves a farmer from so much labor that would ordinarily be needed to clear a plot of ground for planting. The principle at work in the silage tarp system is called occultation. Occultation means to block something from the light. When a tarp is pulled over the soil’s surface, any growing plant material dies and decomposes. Moisture is also retained, encouraging soil biology and speeding up the decomposition process. In addition, any weed seed in the surface level of the soil is induced to germinate, sprout, and then die from the occultation. 

If the ground is not already wet, water it down or wait for it to rain before pulling the tarp over with the black side facing up. With the black side up, it will absorb heat from the sun, which will in turn warm up the soil and encourage germination. If you have done an initial till to create a soil disturbance, any weed seeds on the surface will now germinate, grow, and die. After this process has taken place, you should have a weed-free surface to begin building beds on. Preparing your growing space ahead of time with silage tarps will save you a tremendous amount of time on weeding and cultivating by hand.

The amount of time it takes for a silage tarp to work is relative to the time of year, temperature, and moisture level. It’s important not to rush the process when tarping, ultimately defeating the purpose. Checking regularly under the tarps is the best method. If you are tarping a pasture with native grasses, it may need to be left on for up to a year to decompose the organic material. However, on ground that has been tilled and prepared, weed seed can germinate and die within just two weeks (if the heat and moisture levels are sufficient).

Some grasses are more persistent and harder to kill, such as Bermuda grass. With rhizome roots that can grow and spread in the absence of light, they will often require being dug out by hand. 

The most common spacings for market gardens are a 30” wide bed, and 18” pathways, with bed lengths varying from 50’ to 100’. An 18” pathway allows for a harvest tote to fit comfortably and also limits the risk of accidentally stepping on your crops while working. Narrower pathways can completely disappear as larger crops mature and grow over the pathways. Despite this, maximizing space is the most important thing when growing in a limited space. If growing in 14’ wide caterpillar tunnels, it works well to do four 30” beds with 12” pathways between beds, and 6” from the outer beds to the edges of the tunnel. 

Standard wooden stakes from Home Depot (or the like) work well for marking the corners of your beds.  Once these are driven in, they will remain permanently installed and can be used repeatedly for pulling string lines to show the edges of your beds. When first installing your corner stakes, take your time to measure precisely. 

Once string lines are marking the edges of your beds, the next step in the process is to broadfork the bed. This loosens and aerates the soil, making it more habitable for soil biology soon to be introduced.

After loosening the soil with the broadfork, the next step is to put down a layer of carbon.  Most opt for cardboard as it provides an excellent additional weed barrier and eventually breaks down. Wetting down the cardboard will help facilitate its decomposition and jump-start the biology. Cardboard is readily available (especially in more urban contexts) and is a great option for turning a material that may otherwise end up in a landfill back into the soil. For a larger scale operation, industrial rolls of corrugated cardboard can be purchased from Uline.

When finding your cardboard, look for the largest pieces possible. It will make it the quickest to layout and easier to make your beds. Make sure that the cardboard you’re getting isn’t glossy or painted. Also, make sure no tape or staples are present before laying it down. Slightly overlap the pieces so that no cracks are exposed. However, do not double up the cardboard or use extra thick material. It will take too long to break down into the soil and potentially create an anaerobic environment underneath the cardboard. A single layer is sufficient.

Cardboard should be laid down everywhere—both over the beds and pathways. However, don’t attempt to do an entire field block simultaneously. The wind will blow it all over the place, and you’ll just be running around chasing cardboard. Also, wheelbarrows full of compost can damage the cardboard as they are rolled in. Two beds at a time work well.

Once the cardboard is positioned and wet down, it’s time to add the compost. Layering on four to six inches of compost will come out to roughly two to two and a half yards per 50’ bed. At $30 a yard, that is about $60-75 per bed. This is a worthwhile investment for what will soon yield a high return! 

Once the compost is evenly spread over the beds, wood chips can be brought in to cover the pathways. Layer on the wood chips to be the same level as the compost. They will quickly compress and be lower than the beds, likely needing a second application. Having the wood chip pathways and the compost in the beds at the same level helps to hold everything in place. 

There are many benefits to using wood chips for pathways. The first and most apparent benefit is weed control. From tarping, layering cardboard, and then layering on wood chips, the weeds have no chance to get established. Anything you can do to reduce the time and energy you put into cultivating and weeding is always a win.

Another huge benefit of wood chips is their ability to retain moisture. Typically when you have raised beds, the outer edges of the beds will dry out faster because they’re exposed to the wind and the air. By layering the wood chips at the same level as the soil, they will hold moisture and release it into your bed over time. The edges of your bed will not dry out as quickly as they would without the wood chips.

Biologically speaking, wood chips are also great because they add a lot of fungal life to the soil. The majority of the compost added to the beds will be bacterially dominated. By introducing the wood chips, you add a highly beneficial fungal element, bringing balance to the system. When using wood chips for pathways, they no longer just serve as a place to walk but also as an additional source of fertility and moisture. 

After the initial installation of a bed, more chips will be needed between plantings, but over time as things get established, adding more wood chips will be required less frequently. 

Local arborists and tree companies are a great source to acquire free wood chips. Most of these companies have to pay a fee for dropping their chips at a designated dump site and are often more than happy to dump chips at your property for free—especially when they have a job in your area. 

While you can often get on a waiting list for wood chips to be dropped at your property for free (through services like Chip Drop), you’ll usually have quicker results by reaching out directly and talking to the folks who work there. Developing a working relationship with a local tree trimmer is the best way to go. They will call you when they’re in your area and ask if you are ready for another drop.

One potentially negative aspect of having wood chips in your paths is that they can sometimes creep into your beds, especially if your beds are on a slope. To help curb this from being a problem, quickly rake out whatever wood chips have crept into the bed just before replanting. Raking them back into the pathways only takes a minute and ensures they won’t interfere with direct seeding or transplanting the next crop. Everything takes maintenance, but after the initial installation, wood chips require very minimal maintenance.

Another concern about having wood chips close to growing vegetables is that they could potentially tie up the nitrogen that would otherwise go toward nourishing the plants. However, there are no issues with nitrogen being tied up when they are only on the walkways or even on the surface in the growing space. This would only occur if wood chips were mixed directly into your beds.

In the deep compost mulch system, shallow-rooted crops like lettuce and other greens are recommended for the first planting. If you want to plant larger crops with more expansive root systems (like tomatoes), you can punch through the compost and the cardboard down into the native soil below. Carrots are also possible for a first planting, but they will likely be misshapen if the soil is too compacted. Greens are preferable for the first plantings.

There it is! The complete step-by-step process for installing your own no-till garden beds using the deep compost mulch system. If maintained properly, beds installed in this manner will only get better and better with each passing year. 

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