Series: The Organic Gardening Collection
Compost is our way of mimicking nature, yet speeding it up substantially.
Whereas nature slowly decomposes animal manure, leaves and other organic matter, we put a large amount of these things into a pile in specific combinations and ratios to make it happen quickly.
The forest floor is continually covered with moss, ferns, leaves, needles, tree branches and trunks in various stages of life and decomposition.
Compost is not natural. I love making and using compost, but it’s worth remembering that.
Nature makes humus by covering the ground in plants that continually grow and die throughout the seasons and years.
Masanobu Fukuoka points out in The One-Straw Revolution that we don’t need to compost if we maintain plant cover and mulch.
This is true. The reason we compost is just to speed things up a little bit, particularly when we’re dealing with degraded soils. It works, but it doesn’t mean we should forget about mulching and maintaining plant cover.
We add compost to our soil to quickly increase the number and diversity of microbes and small animals, organic matter content, and nutrients in our soil, all of which are often low because of past gardening or other land use practices.
A lot of resources refer to the organic matter and nutrients, but fail to focus on the microbes.
The way compost breaks down is through the action of microbes, earthworms and insects. Their numbers multiply many times in the pile, and to me, they are the number one reason to compost. For most of us, getting that biology back into the soil is more important than using fertilizers.
How much compost should you make?
As much as you’re willing to make. I’ve never heard a gardener complain of having too much compost. That being said, it’s better to concentrate your efforts on one properly managed pile than many, poorly managed piles.
And as you’ll see, you actually need very little compost to get big benefits. And you don’t have to get too scientific about it, but you do need to do a few things right. Poorly made compost can be plant-toxic putrefying organic matter.
I’m not going to list all of the materials you can use in your compost.
People often think of compost primarily as a way to dispose of food scraps. But you won’t get high quality compost if that’s all you put in.
Obviously, use good judgment, but pretty much anything that was once alive can go in there. The more variety in your raw materials, the more diverse the resulting compost.
As you’ll see, I don’t use any genetically modified materials (GMOs).
The three most common ingredients in compost are:
- Plant parts such as leaves, weeds, grass clippings, wood chips and straw
- Food scraps
Useful supplementary materials include newspaper, cardboard and sawdust. You can also throw in dryer lint, tea bags, animal hair, vacuum cleaner dust and so on, but these will make up just a tiny portion of the pile.
There are dozens of materials out there. Some of them are available only in certain regions.
Perhaps you have a beet processing plant or an apple cider producer near your house. These processes make wastes that can be composted, as does residue from cocoa beans, coffee, wineries and breweries.
I taught a composting class for Gaia College where we used a nitrogen-rich material called okara, a soybean by-product from the manufacture of soymilk, tofu and tempeh.
Okara is a pulp consisting of insoluble parts of the soybean that remains after pureed soybeans are filtered in the production of soy milk and tofu.
You may not have enough stuff on your property to keep a good pile going.
For this, get food scraps from your friends and neighbors and offer to take their leaves in the fall.
Find a farm or orchard with some spoiled hay or fruit. While you’re out there, find a source of organic animal manure from a farm or stable. This isn’t absolutely necessary for the pile, but will definitely improve it.
If you have many forests in your area, you’ll probably find someone selling or giving away sawdust or wood chips. In the city, find breweries, canneries or other food processors.
In the long term, a good goal for achieving a more sustainable garden is to use at least 50% of your garden beds to grow this biomass.
Some of it can be turned into the soil, and some of it can be composted.
Grasses and legumes are the best for this. To be as close to being sustainable as possible, we should really be composting our own human manure, too, and maybe even have some of our own animals that make manure for the garden.
Carbon and Nitrogen
We loosely categorize our materials as being carbon materials and nitrogen materials.
Carbon materials tend to be yellow-brown and dry, so they’re often referred to as “browns.” They can have anywhere from a 30:1 carbon to nitrogen ratio to hundreds of times as much carbon as nitrogen.
Nitrogen materials tend to be wet and often green, so they’re often called “greens.” Despite the “greens” name, they still have more carbon than nitrogen, but the ratio is generally much lower — between 10:1 and 30:1.
Just because something is actually brown in color doesn’t mean it’s necessarily a high-carbon material. Chicken manure, for example, is definitely a “green,” though if it actually looks green you should check what you’re feeding your chickens.
Chicken manure has among the highest nitrogen percentages of all manure types.
Carbon materials, roughly in order of increasing carbon content, include leaves, straw, hay, paper/cardboard, and wood/sawdust.
Nitrogen materials, roughly in order of increasing nitrogen content, include manure, seaweed, grass clippings, alfalfa hay and food scraps, although manure varies depending on the animal and the freshness.
In reality, all of these materials vary based on different factors. Kitchen scraps, for example, can range from being high in nitrogen to a moderate 25:1 carbon to nitrogen ratio.
You can find many reference charts online with carbon to nitrogen ratios for common materials. It’s worth checking more than one since they don’t always agree with each other’s estimates.
Most experts tell you not to compost cat and dog manure because they contain pathogens. I think we just need to know how to make a good pile that will kill most of the pathogens.
Obviously, we don’t want our pile to be 50% dog manure. It will more likely be 2% dog manure, and that’s just fine.
It’s true that these manures contain pathogens. Cat manure contains a microbe that is hazardous to children and fetuses in the womb. It’s just as hazardous in the litter box and out on the lawn, so my opinion is that composting it is fine, as long as you’re building a proper compost.
Experts also say not to compost diseased plants, but I disagree.
First of all, most pathogens will be killed in a well-made pile, and perhaps more importantly, their predators will be given a reason to flourish. We need some disease around in order to keep the predators that eat that disease around, so I put all diseased plants right into the pile.
It might be worth making an exception if you have garlic with white rot, which can take over 20 years to clear from the soil once an area is infected.
About the only things I don’t compost are toxic materials such as colored paper and carpet, and noxious weeds such as quackgrass and bindweed that may survive the composting process and be subsequently spread throughout the garden.
But yes, I use oak leaves, pine needles, cooking oil, ashes, and even a small amount of meat in the middle of the pile.
If all of this sounds like a bit of work, it is.
If you have more money than time, you can pay someone else to do it for you or buy compost, as long as it gets done. Using compost may be one of the most important things you can do for your garden.
Activators are extra substances that stimulate the composting process. They can be synthetic substances, which I don’t recommend using, or they can be natural.
Activators aren’t crucial, so if you want to keep the external inputs to a minimum, you don’t need them. People who are really into making the best compost may enjoy using some of them, but there is something to be said for keeping compost simple and using materials from your site as much as possible.
Some of the potential benefits of using activators are a faster time for the pile to finish, a better-finished product and less odor.
Some activators such as clay, humates, calcitic lime and gypsum also decrease nutrient loss from the pile, especially nitrogen, which is a big deal.
Gypsum is a minderal amendment made from calcium sulfate – not to be confused with drywall, which usually has additives you don’t want to put in your garden.
When I’m building a new pile, I inoculate it with finished compost, generally as much as 10% of the pile or even just a few shovels if that’s all I have.
I’ll also add as much as five pounds of humates per yard of raw materials, although that can get expensive.
It seems counterintuitive to add them when the ultimate goal of compost is moving it towards becoming humus, but adding humates can drastically improve the composting process.
I use as much as 10% clay in the pile.
You generally don’t want to add clay directly to sandy soil, but composting it gives it a chance to form a clay-humus complex.
Even if I have clay soil, I’ll add some to the pile to get this complex happening, because it helps the organic matter stay in the soil. Bags of bentonite clay are great, or even just a clay loam soil works well. This can get expensive, too, but even a small amount of clay is very useful.
I’ll cover Effective Microorganisms (EM) and biostimulants another time, but I will mention here that inoculating the compost with EM will speed up the process and may contribute to a decomposition that is more controlled and less oxidative so that nutrients are better retained. Odors are also greatly reduced.
I do this whenever I’m spraying the rest of my garden on a monthly basis.
Rock dust is an incredible addition to the compost.
Just sprinkle it in as you build the compost or work it in from the top. The nutrients have an opportunity to bind with the organic matter and are thus more effective when they’re eventually incorporated into the soil.
No, not that kind of rock dust.
The dust will also improve the composting process. Different experts say to apply anywhere from 2 to 50 pounds of dust per cubic yard of compost.
I use 20 pounds and I use a non-quartz dust such as basalt rather than something like granite. Quartz contributes less value to the pile and can inhibit proper humus formation.
If you’ve determined from a soil test that you need certain nutrients in your soil, it’s great if you can first add them to your compost.
Products such as calcitic lime and soft rock phosphate will bind with the organic matter, just like the rock dust.
In fact, even without a soil test, it would be entirely appropriate to add five pounds of calcitic lime per yard of raw materials when building the compost, as it is so crucial to the microbes in the pile.
Alternatively, five pounds of gypsum works well to get things moving, perhaps because of the sulfur. Otherwise, don’t indiscriminately add mineral fertilizers because we may not want the nutrients contained therein. Urine, on the other hand, is exceptionally good for the compost, admittedly a bit easier for guys.
I have used a series of preparations from the biodynamic world. More on these in a future lesson.
It’s a bit of work for city folks to find manure, but it does play an important role in the compost pile for its nitrogen content and microbe population.
A pile can be made without manure, but it can be difficult to find enough food scraps and fresh plant matter to supply adequate nitrogen. That being said, I’ve spent the last few years as a vegetarian and a vegan, and certainly support using compost that doesn’t contain manure if you prefer.
Fresh manure should not be applied directly to the soil for several reasons. The high nitrogen content can burn plants, and nitrogen can leach into the water table and volatilize into the air.
The high salt content can also cause problems. Other excess nutrients such as potassium can imbalance the soil.
Weed seeds that weren’t broken down by the animals’ digestive processes can be spread throughout your garden too. Composting the manure in a well-made compost pile helps with many of these problems. Some nitrogen is still leached and volatilized, but much of it ends up in the bodies of microbes. Composting manure first means salt and excess nutrients are buffered and weed seeds are killed.
Different manures have different characteristics. A mixture of manures is ideal, but just go with whatever kind you can get your hands on, keeping in mind the health of the source animals.
I don’t know if there’s research to back this up, but llama manure is widely reputed to be among the best as a soil amendment and nutrient source.
Non-organic farm animals receive antibiotics, hormones and dewormers, some of which can survive the composting process. They certainly decrease the number of beneficial microbes that end up in the manure.
Chickens may be fed arsenic and their manure may have been treated with alum, which ties up the phosphorus, rendering it unavailable to plants.
Mushroom manure is horse manure that has been used to grow mushrooms.
It may contain huge amounts of pesticides and excess calcium, which is added to grow the mushrooms. Basically, we want organic manure.
Chicken, sheep and rabbit manure are generally considered the highest in nitrogen, and horse can be good, too. Pig and cattle manure are lower in nitrogen, but cattle manure is said to be rich in microbes.
Even your own manure can be used if you’re not taking pharmaceuticals. Just make sure it’s properly composted first.
The best places to go are where there will be manure that isn’t going to be used. Horse stables are a good bet and the manure is already mixed with straw, so it’s very easy to handle.
Poultry and dairy farms are okay, too. Small hobby farms aren’t as good because they probably use all of their manure on site. You can even go ahead and buy a few bags of manure at your garden center, but it’s already been composted and it may have nasty substances added. Check the label.
Many gardeners will prefer buying compost from a garden center or the municipality.
I have never lived in a city where I found great compost, but there is usually something acceptable.
I lived in one city where gardeners flocked to pay $75 per yard for a compost made with fish waste and coniferous bark, complete with coniferous toxins. I didn’t like the stuff much and gardening friends determined it had a calcium deficiency, but other people loved it and used it successfully.
When buying compost, it should smell good, not like garbage.
I shouldn’t have to say it, but it should not contain garbage. I once received a load of 15 yards of compost that was full of pieces of plastic, produced by a recycling company. I got my money back.
Most purchased compost will not have been properly cured, so although I know it’s not often feasible, if you have a month or two to let it continue composting on your property, that would be good.
Ask about the raw materials.
Is there toxic paper mill waste or household waste, or pesticide-laden grass clippings in it?
Don’t use compost that has been made with sewage sludge. Yes, an argument can definitely be made that we should be composting this stuff rather than sending it raw to the landfill or our waterways, but we shouldn’t be putting it in our gardens.
A biosolids (aka sewage sludge) processing plant.
Most of the pathogens can be destroyed, but a smorgasbord of heavy metals, pesticides and other chemicals survive the process and end up increasing in concentration. The sewage sludge industry may try to tell you differently, but there is plenty of research available on this.
The best time to apply compost is in the spring and fall when the conditions are best for the microbes, although if you’re doing intensive composting throughout the year, you may apply it every month.
In the spring, I apply it at least two weeks before planting to give some time for it to get acquainted with the soil.
You can apply compost in the fall, but if you live in an area of high rainfall, you may want to cover your compost pile for the winter and wait until the spring to apply it, in order to avoid leaching some of the valuable nutrients from it.
If I’m using compost to make a new garden bed or install a new lawn in a soil without much organic matter, I’ll often work a couple of inches of compost into the top 8-10 inches of soil. That’s generally too much compost to use more than once in the same garden, but for a soil that is low in organic matter, it’s useful to get that in there in the beginning.
For maintenance on existing beds, I’ll apply between 1/8 inch and 1/4 inch to the surface. I may lightly incorporate it, but I don’t do much tilling for maintenance.
Using a fork to lightly incorporate compost into the top few inches is much kinder to the soil that “turning” it in a conventional way.
For an existing lawn, you can screen out sticks and big clumps and apply it at 1/4 inch thick. If possible, do this as often as annually.
The Luebke’s, who developed Controlled Microbial Compost on their organic farm in Austria recommend 10-12 tons per acre to start and then down to 3-8 tons for maintenance. Elaine Ingham recommends a maximum of 10 tons per acre and more like 1-5 tons per acre for maintenance.
By my math, 12 tons per acre is only about 2/5 yard of compost (1/8 inch thick) per 1,000 square feet and 1 ton per acre is only about seven gallons of compost (1/90 inch thick) per 1,000 square feet.
You can see that even a tiny amount of compost is beneficial, so you don’t need to worry about making or purchasing tons and tons.
This planting hole could stand to be a bit wider, but the cuteness makes up for it.
Instead, most home gardeners need only make or buy 1 yard of high-quality compost each year. While the organic matter is important to get in there in the beginning, the nutrients and microbes may be the most important part and even seven gallons of good compost can supply plenty of them.
Many gardeners and farmers apply too much compost, which results in nutrient imbalances, nutrient leaching and subsequent pollution of our waterways, and volatilization into the atmosphere as greenhouse gases.
When planting trees and shrubs, rather than backfilling the hole with compost, amend the entire planting area at least twice as wide as the planting hole by incorporating compost into the soil.
We want to enrich the soil, but we don’t want to make the planting hole so rich that the roots don’t leave it.
Finished compost can be used as part of a potting mixture and for seed starting at about 1/3 compost, 1/3 sand and 1/3 soil. If possible, let this mixture age for a month or two before planting into it.
- Leaves, weeds, grass clippings, wood chips, straw, manure and food scraps are the main compost ingredients, along with supplementary materials such as newspaper, cardboard and sawdust.
- Compost, urine, humates, clay, EM, biostimulants, rock dust, mineral fertilizers and biodynamic preparations are activators that can improve the composting process.
- Manure is one of the most important ingredients for its nitrogen content and microbe population, as long as it is from animals that are healthy, happy and drug-free.
- I often use a couple of inches of compost in a new bed, but as little as 1/90th of an inch can be extremely beneficial.