ON-FARM COMPOSTING

Is it worth the effort to make your own compost on a small-scale farm? If you decide that it’s not, what do you do with your old crop residue? 

Most would agree that it’s often not feasible to create enough compost to meet all the fertility needs of your farm, especially on a small piece of land. This is especially true for those trying to increase the organic matter in their soil, or for those practicing the no-till deep compost mulch system–which takes A LOT of compost (especially when first building beds).

The volume of compost needed to operate a small-scale, not-till, high-yielding farm is significant. If building beds using the deep compost mulch system, it can take up to 2 yards of compost for one 100’ x 30” bed. 

In addition to the sheer volume needed, you likely can’t make the same quality of compost that you would buy from a professional. High-quality compost on a large scale takes a lot of time and effort to produce. It requires a wide variety of inputs that could be challenging to produce from your own property. Plus, you would need to have some pretty expensive machinery to move the material, mix it, and maintain it. You’d also need the space to store it.

As you continue down this path you quickly realize why compost companies are formed. Producing a high volume of quality compost is a full-time endeavor in and of itself. And anyone who has farmed full-time knows that time is often the most limiting factor.

However, if you decide to go ahead and outsource your compost, you can still have a small and relatively low-maintenance compost operation on your farm. This could simply be a series of basic piles or a multi-stall unit built from repurposed pallets. Having something like this in place allows you to use your spent crops and other organic material from your property to create a supplementary source of fertility.  

You may be asking yourself, “why invest the time and effort to make my own compost when I’m already paying to have the bulk of it delivered?” Think about it this way: you’ve worked so hard to build up the life of your soil, added amendments, added compost, and have worked hard to protect it from erosion by keeping it covered. 

Doesn’t it seem like a worthwhile effort to use that residual crop material that your soil has produced, and turn it back into more usable fertility? You’ll have to remove that material regardless when you flip your beds and prep them for the coming crops. If you don’t compost it intentionally, it will likely just get piled into a heap somewhere on your property where the majority of the nitrogen would escape back into the atmosphere. 

With just a little extra effort of intentionally layering that green material with some dried-out carbons (like dead leaves or straw), and watering it in, you can bond that nitrogen to the carbon and turn it into an amazing nutrient-rich material to feed back to your soil! 

You also get the gratification of turning what would have otherwise been waste into usable nutrients for your plants. You’re not only helping the environment, but you’re also creating a usable fertilizer to give back to your soil AND your plants. 

Some compost methods are centered around the quickest turnaround from raw materials to a finished product, while others are more passive and take a longer time to complete. 

In the scenario where you aren’t relying on your homemade compost for production (but are instead out-sourcing for the bulk of it), a slow processing time isn’t necessarily a drawback. Slow compost is also less maintenance. You aren’t worried about turning the pile to reintroduce air and heat up the pile again. It can take six months to a year to create cured compost using the slow method. 

Speeding up the process of converting organic material into finished compost requires quite a bit more work. Materials need to be shredded or chopped and piles need to be consistently checked for temperature and moisture levels. Piles will also require multiple turns in order to reintroduce air and accelerate the process. 

Whether you’re using simple piles or building pallet bins, positioning your compost setup in close proximity to your growing space will reduce your footsteps and help you stay more consistent with composting. Also plan to have a water source near your compost setup in order to water your piles.

General compost piles should have at least one cubic yard for the volume to generate enough heat. Standard pallets are typically about 40” x 40” and work well to accommodate about a cubic yard of compost.

If you do decide to build compost bins out of pallets, the number of bins depends on the size of your farm and how much material you’ll need to process. Always create a station with more bins than you think you’ll need. Five to seven bins is a good starting point. Additional bins are also nice for storing finished compost. 

Many people use chicken wire or other kinds of wire mesh for the sides of their compost bins to hold in the material while increasing airflow, but scrap wood side walls (with small slats for some breathability) can help retain more moisture if needed in your context.

It’s often recommended to layer a compost pile with a ratio of 30 parts carbon to one part nitrogen. While this sounds good in theory, not everything is just carbon or just nitrogen. To get close to this ratio (practically speaking), try to layer a pile as follows:

1. 6-8” of carbon (“browns” – dried out material like wood chips, straw, leaves, paper, bark, etc.)
2. 3-4” of nitrogen (“greens” – fresh cut materials like crop residue, kitchen scraps, grass clippings, etc.)
3. Sprinkle of soil (just a trace of living soil in the mix will introduce more microbes needed for breaking down the material)
4. REPEAT!

Note:

• Water the pile after each layer, as moisture activates the decomposition process.
• If not using pallets or bins, attempt to make your pile a 4’x4’ square, as pressure will be more evenly distributed than in a circular or “mounded” pile.
• Whenever layering a pile, always end off with a layer of carbon. This seals in any odors from fresh green material and “traps” the nitrogen, as well as holding in the moisture.

Use a tarp or black plastic to keep your piles covered. This prevents drying of the piles, and it also protects from oversaturation in heavy rains. Even moisture levels will keep the biology healthy and active.

When it comes to inputs for your compost, what you put into it is what you’ll get out of it. If the inputs are mostly homogenous, your finished product will lack biological diversity and have less to offer your plants. A rich variety of inputs will result in a biologically complex, nutrient-rich compost product. 

A big advantage of growing diversified vegetable crops is the ability you’ll have to provide a large source of diversified inputs for your compost. In addition, household food waste (such as fruit and veggie scraps, coffee grounds, eggshells, etc.) can also add to the variety of your nitrogen sources. Just be sure to immediately cover any of this material with plenty of carbon so you don’t attract rodents and flies!

Unless you have a lot of trees on your small farm to collect leaves, or a chipper to create wood chips, carbon sources may need to be brought in from off of the property. When finding a local source for your carbon inputs, ensure you know where it originated and find out if it was sprayed with pesticides. This material will be spread all over your farm, so it’s essential to make sure inputs are not contaminated. 

If you have bed space available you can also grow certain crops specifically for creating a lot of carbon-rich biomass for compost. These would include crops like sorghum, amaranth, fava beans, sunflowers, lentils, and corn. Let these crops grow to maturity, and then “chop and drop” them to dry out and be used for carbon inputs in your piles!

If you don’t have access to a large volume of leaves on your own property, local municipal operations typically allow you to acquire leaves for free, or at least for a low price. Leaves break down quickly and are nutrient-dense.

If leaves are hard to come by, straw is a viable carbon source and is usually available. Do not use hay; it contains a high volume of seeds. That is the last thing you want to be broadcasted over your beds! Hay is the first cutting (with the seeds), and straw is the second cutting (with no seeds).

Wood chips are a good carbon source for your compost pile, the only caveat being that they take a long time to break down. Using wood chips will mean a lot of sifting when preparing your finished product. 

For the biology in the soil to do its job, your compost will need moisture. If the compost pile is too dry, the microorganisms will not be able to sustain life. Conversely, if the pile is soaking wet, it will become anaerobic (lacking air) and very smelly. Balanced, even moisture is the goal. Some say the ideal is a pile with the moisture level of a “wrung-out sponge.”

In some situations after cropping out a bed, you’ll have fresh greens still alive and full of moisture or fruiting plants like squash or tomatoes. With these inputs, you don’t need to water your pile as much; the ingredients already have high water content. There will be other times when the inputs are really dry and need more water. 

Inoculating your compost pile refers to adding a small amount of nutrient-rich, biologically active compost to a new pile to introduce the microorganisms. Once your compost system is rolling, you can use compost from a pile that’s further along to inoculate your newest pile.

When first starting out, it’s a great option to get some active compost from a friend or neighbor and add some into your first pile. You can also go to a local forest and harvest some compost from the forest floor that looks really healthy. Or, if you know of a wood chip pile that has been sitting for multiple years, digging into the center will yield some fantastic compost for inoculating your pile. It doesn’t have to be much–just a small bucket will do.

The “add as you go” approach to layering compost piles is typically what makes sense on a small farm. Piles will heat up the most if layered all at once (built up to 4’x4’), however, having this much material on hand isn’t always the case on a small farm.

Anytime you are cropping out a bed, the crop residue can be taken directly to the compost bins and layered into whichever pile is currently being added to. You can also store the material next to your compost piles to be layered in at a later time. 

After you’ve reached about 4’ high when layering a pile, give it a final watering and then tarp it. If you want to speed up the process you can flip the finished pile after about four weeks–when the initial heat of the finished pile has cooled back down.

“Flipping a pile” means transferring the material from one bin to another (typically immediately to the right). The goal is to get all of the undecomposed material from the exterior of the pile moved to the interior, where it will have the opportunity to continue breaking down. This process also reintroduces air into the pile, which re-excites all the microbes and heats the pile back up.

When you flip the pile after the initial four weeks, it will then take another 10 weeks before the pile will be fully composted (where the original material is unrecognizable).

If accelerating the process is not your goal, you may skip the step of flipping the pile. Some studies have shown that by taking the longer more passive approach to making compost (without reheating the pile), the cured compost product will be more nutrient dense for feeding your crops. 

Finished compost will be dark and moist, with a sweet earthy smell. It’s normal to see some larger aggregates that have not fully decomposed. If you plan on using the compost in a bed that will be direct-seeded or as a potting mix in the nursery, sift out the larger chunks through a screen. However, in beds you transplant by hand, the larger chunks won’t interfere and can be left in. 

A hand screener is a simple wooden frame with hardware cloth wire mesh. You place a hand screener over a wheelbarrow and pour the compost through, sifting it into the wheelbarrow. It helps to have one person shimmying the frame of the hand screener over a wheelbarrow, while another person shovels in the compost.

Another sifting option is a trommel. A trommel is a rotating cylindrical sieve for sifting coarse material. You can make your own trommel for sifting compost using a cement mixer, a garbage can, and hardware cloth. This system is more efficient and less labor-intensive than a hand sifter. Larger material sifted out of the compost can be tossed back into a pile to continue breaking down. 

It’s good to have a compost thermometer to periodically measure the temperature of your piles. An important note about compost temperature: if you use the compost on a certified organic farm, it’s required to heat the pile between 131-170° F and maintain that range for three days. 140° F is a good target for the initial heat of your piles. Temperatures beyond this can actually “burn off” a lot of the organic matter that could otherwise become cured compost. To reduce the heat of your piles, decrease the amount of greens (nitrogen), and increase the amount of browns (carbon).

Making the most of what you have, and turning what would otherwise be waste into usable fertility is always a win! It’s not that much extra effort to turn your old crop residue into an amazing source of fertility–so you may as well. It’s a gratifying feeling. Go for it!

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