MULCH//The Deep Mulch System, Step-by-Step
The deep mulch system is at least the second most well-known form of no-till (behind roller-crimping cover cropping), but it’s also arguably the most accessible. In a sentence, cover with compost and plant. That said, let’s really get into the nitty-gritty and go step-by-step into how to establish a deep mulch no-till system and look at some of the nuances. If I miss anything, or if you have a question, please add it to the comments section.
Step One: Locating Compost
Finding good compost is going to be your greatest obstacle in a deep mulch system, so that should be the very first thing you do. If there are no compost suppliers within range, and nowhere to get bulk materials for your own compost (or no way to make your own in bulk) you may have to look into some other system.
Ask organic and/or local farmers in the area what they use. Check with landscaper supply places. Tree trimming services (or your local electric company). Call around. Check with the ag department (or food services) of your local university. Google. Craigslist. Really put some work into finding compost nearby.
You can expect to pay anywhere from $20 to $40 a yard for finished compost (do not pay that much for raw material). Account for 1.5 to 2 yards per 100’ x 30” bed to start (then as little as .3 yards per bed every year after depending on cropping). If you’re able look at the compost you are hoping to purchase before you buy it, do so. Getting a feel for the physical composition is important. Are there large pieces of carbonaceous materials? Is it sifted and fine? These properties will determine things like water retention, ease of seeding, etc. Ask the composter what materials go into it to make sure there is nothing detrimental to sensitive plants (i.e. herbicide residue, invasive weed seeds, anything questionable). Even better, get a sample and have it tested to make sure you know what you’re working with since you’ll be working with a lot of it.
That said, you do not have to exclusively use perfect compost for this project. In some ways, especially if more affordable, basic mulching compost (the chunky stuff) will be fine. You can always add good compost tea and cover crops to help steer it back to vitality and use other sources of fertility in the meantime.
Step Two: Get a Soil Test
Before you cover your soil, an Albrecht soil test with mineral recommendations is essential. You need to know your soil organic matter and the mineral content. If it’s low (below 4% or so), you may want to work in the recommended minerals and some better compost in a one-time till. This tillage is something that almost every microbiologist I’ve seen speak—or spoken with personally—has recommended. Covering compacted soil will not de-compact the soil, at least not immediately. Getting those microbes, carbon, and minerals in, however, then mulching, is important in the short-term, because you have bills to pay.
Step Three: Break Ground (if not already in garden)
If you’re going into pasture or fallow ground of any sort, you will need to do some work before you can cover. So far as I can tell, you have three options:
Slow: mow, tarp the area until dead (preferably for a full season), amend soil, then add compost.
Faster: mow the area, cover with paper/cardboard mulch, add compost.
Fastest: plow and till it, then cover it with compost.
You will want to make sure you are not leaving grasses alive and ready to thrive in the new compost. Whatever you can do to kill and/or firmly suppress it beforehand will be greatly appreciated by future you. Trust me.
Step Four: Bed Layout
Choose the bed width that works best for you. 30” is nice in that you can step over it easily and work the full width of the bed from one side. Most of the hand and long-handled tools for small-scale farming are designed for this bed width as well. However, 36” or even 42” is better for spacing as more can fit in the bed and less garden space is dedicated to walking paths. Consider how much space you have: if you’re quite limited I would go with larger beds and tighter paths, if you have plenty of room and want to make it a little easier to get around, you can use smaller beds and/or wider paths. Just keep in mind, paths don’t make you money and take work to maintain, too. It’s your call, but bed width will change the above noted compost quantities to go with wider beds. More on that below.
East/West vs North/South is less important than orienting your beds facing slightly downhill so the water drains. I did not do this and it was a huge mistake. I get erosion issues from excess water running across beds. It is to some extent only during the crazy deluges we’ve seen (70+ inches this year here in KY), but I do believe facing beds downhill is more important than orientation, especially if heavy intermittent rainfall is going to become more frequent. If you will be growing a substantial number of taller crops like sweet corn or okra that will cast shade, than your cardinal orientation may be a concern, but I would shape my garden plan around that, not my garden layout. Garden layout should be more about working with the terrain.
Step Five: Cover
Covering can be done with something as simple as a wheelbarrow or as awesome as a self-loading tractor-mounted compost drop spreader. For a wheelbarrow, I don’t recommend dumping a full load and trying to spread it out. Dump the barrow in parts, or scoop it out with a five gallon bucket, and spread with a bed rake. If you have an innovative, time-saving, or back-saving method of moving compost around, let us know in the comments, just don’t rub it in my face…
The depth at which you should cover your soil is up to you. Personally, I like 4-6 inches. Keep in mind, the more you add, the more weed-suppression for a longer period of time, but also more work and expense. When you multiply this out over a seasons worth of beds, it accumulates fast. If your ground is already relatively weed free, then I say less is more.
Here’s how to calculate how much compost you’ll need:
([bed width in “] x [bed length in “] x [“ of compost desired]) / 46656 or the number of cubic inches in a cubic yard = # yards of compost for each bed.
If you have access to cheap enough materials and the ability to make a lot of compost, you may choose to cover the entire plot, paths and all. The calculation is a little easier, just (plot L” x plot W” x D“) / 46656
Get at least 10% more than you need, because moving bulk materials around a farm is never clean.
Protip: once you establish your bed layout, use permanent bed stakes to avoid bed/path creep and save steps.
Step Six: Seed & Plant
You can seed directly into deep mulch, but make sure the seed stays moist. I recommend a bed roller as deep mulch can create air gaps that may dry out seeds. The soil below will be plenty moist, but mid-compost can get dry and—not to mention—hot AF in the summer. I like overhead irrigation and covering with row cover. Drip does not work as well in this set-up, at least not until the plants are established and deeply rooted.
Transplanting is just transplanting. Note that the blocks do not need to hit actual soil, but—like the seeds—should get packed in well. Over time, the compost will break down enough to make this a little easier. The first year will take some observation depending on the texture of your compost.
Notable Considerations:
Before you cover up a bunch of ground with compost, check to make sure you’re not feeding bindweed or Johnsongrass. If you have an invasive weed issue, that should be managed prior to covering if at all possible.
Your compost should be free of contaminates and—if certifying organic—all the rules must still be heeded. Also, make sure the compost is weed free if at all possible. Some places certify their compost as such.
If you have anything to add (or possibly subtract), please do below in the comments! Note that we will breakdown other methods, so this will not be the only no-till method we detail in this way. We opened with this one because it is the method we are most familiar with and use ourselves.