Making and using organic compost are the most important things you can do to improve your garden.
Make Organic Compost for Your Garden
Rural author Wendell Berry once wrote of the farmer, "He
has seen the light lie down in the dung heap and rise again
in the corn." These words have sharply clarified for me the
agricultural life cycle — or, even better, light
cycle . Plants convert solar energy into food for
animals (ourselves included). Then the wastes from those
animals, along with dead plant and animal bodies, "lie down
in the dung heap," are composted, and "rise again in the
This cycle of light is the central reason that composting
is such an important link in organic food production: It
returns solar energy to the soil. In this context, such
common compost ingredients as onion skins, hair trimmings,
eggshells, vegetable parings, and even burnt toast are no
longer seen as garbage, but rather as sunlight on the move
from one form to another.
By making use of such substances, composting enables us to
have large amounts of "dung" for our gardens without
necessarily passing most of the ingredients through an
animal first. It also greatly speeds up the earth's own
soil-building processes so we can get the results in months
instead of centuries.
The benefits of using organic compost are so legion that it's no
exaggeration to say that it is the key to soil
fertility. The end product of composting is humus
, the broken-down organic matter that is the basis of soil
life. And the billions of microorganisms that are in a
single teaspoon of fertile soil perform numerous
functions. They change nutrients into a form that your
plants ran use . . . provide a sustained, ongoing flow of
that food . . . and bind earthen particles into small
aggregates, helping to build a friable soil.
There are other benefits of organic compost:
Control of pH. Acid or alkaline soil can lock up
many nutrients so that they're unavailable to plants. The
regular addition of compost rounds off such sharp edges,
helping to bring soil to the crop-favoring pH range of
between 6.5 and 7.5.
Heat absorption. Finished compost will help
darken most soils, helping them to better absorb heat from
sunlight. This can actually extend your spring and fall
Drainage, water retention, and aeration. Imagine
the life of a root for a moment, ever tunneling in search
of water and food. If the soil is clayey, the roots will
have trouble making headway. They become shallow, never
reaching the food and water reserves deeper down. And their
oxygen supply is easily cut off in the tightly packed soil.
Sandy soil creates a different problem; it's like a long
stretch of good road with nowhere to get food and water.
Nutrients and moisture simply percolate down out of reach.
So we want it all — good drainage, good water
retention (even though the two sound almost contradictory),
and openness for the incorporation of air. Again,
humus is the cure-all. It opens up packed soils and binds
together loose ones. Acting somewhat like a sponge, humus
helps hold moisture, food, and air so plants can have
access to them at will.
Nutrient retention. Chemical fertilizers provide
quick-fix doses of three major nutrients: nitrogen (N),
phosphorus (P), and potassium (K). Since such garden
additives are highly water-soluble, plants can take them up
quickly, but they can also be easily washed away by rain or
irrigation. In fact, it's estimated that from 25% to 85% of
the chemical nitrogen applied to soil and 15% to 20% of the
phosphorus and potassium are lost to leaching.
Humus holds those water-soluble nutrients inside itself,
keeping them safe from runoff and releasing them slowly to
plants. (Even better, the soil microorganisms in humus
release nutrients more slowly during cool weather —
when crops are growing more slowly — and most quickly
during warm weather, when plants are growing most
Free choice feeding. The way in which roots and
humus directly interact is probably the most fascinating
argument that I know of for the use of compost. It's a
miraculous process whereby plants choose their own diet.
You may have seen the words cations exchange on a soil
test. Cations are positively charged molecules of different
minerals like ammonium, iron, potassium, magnesium, and
calcium. Since opposites attract, the negatively charged
molecules of humus (and, to a lesser extent, clay as well)
attract and hold the positive canons.
When a searching root comes along, surrounded by an aura of
positive hydrogen ions, it strikes up a friendly exchange
with the humus (or clay) molecules: The root trades its
hydrogen ions for the nutrient ions of its choice. Thus
humus allows plants to choose what nutrients they need.
And more. Compost also helps control nematodes
and soil diseases . . . attracts soil-building earthworms .
. . helps plants produce their own growth stimulators . . .
helps fix heavy metals and other toxins in the soil
(instead of letting them be absorbed by the crops) . . .
adds trace minerals to the soil . . . and makes plants
hardier and more resistant to insects and diseases. It can
even be used as a healing poultice on tree wounds!
Last, compost can be made virtually free at home, by
mimicking the earth's recycling system. Chemical
fertilizers, on the other hand, cost money and use
nonrenewable fossil fuels (both as ingredients and in their
Composting requires nitrogen, carbon, air, water, mass,
Where to Compost
Well, are you convinced? I hope so. Composting really is
the backbone of good horticulture.
If you are ready to start your own pile of black soil
magic, the first concern is where you'll build it.
When choosing a spot, take into account these suggestions:
1. Try to locate your pile near your garden — a
wheelbarrow loaded with compost is heavy.
2. If you're going to be importing some compost-building
ingredients by vehicle, try to build your pile in a spot
you can drive to.
3. Wetting the pile will be a lot easier if you locate near
a water source.
4. A good deciduous shade tree near the pile can provide
some shelter from heavy thunderstorms and excessively hot
summer sun, while it lets warmth-boosting fall and winter
light through. It'll even provide leaf material! However,
evergreens (which have acidic needles), walnuts (which
exude a toxin through their roots), and eucalyptuses (which
have resinous leaves) are not good choices.
Compost In What
Now we need something to put your ingredients in. Actually,
a straight-sided pile can be constructed with no bin or
supports. That's a perfectly acceptable way to compost.
But it takes time to shape a freestanding pile; being able
to toss the makings into a container can really speed the
process along. In addition, if your neighbors live nearby,
they may voice aesthetic objections to a freestanding pile
of decomposing materials. In that case, you can compost
incognito by using an attractive homemade or commercial
bin. Privacy fencing (plant or wire) might also help shut
out the critical eyes.
The creative scrounger will find that numerous materials
make good bin buildings. Boards, poles, screen, wire, old
pallets, concrete blocks, snow fencing, and hay bales will
all serve well. At the other end of the spectrum are the
$70 to $200 commercial composters you can buy through
garden supply catalogs.
In the middle, between total scrounging and total spending,
are the two composters we recently designed at MOTHER EARTH
NEWS. The "quickie" version is a mobile
pen made out of hogwire panels. This low-cost model allows
you to use it to make a pile and then easily move the pen
when you want to start a new pile or turn the old one. The
"uptown" model is meant to be more aesthetically
acceptable, yet still entirely practical. Although you
could build it with just one bin (the design is basically
modular), you'll do better if you build more than one
enclosure so you can turn compost from one bin to the
other. Better still, build a three-bin version so you can
turn two half-decomposed "side" piles into the middle bin
to finish cooking!
Any pile, freestanding or contained, should be at least 3 feet
by 3 feet by 3 feet to insure that there's sufficient mass for the
composting process to take place. I find 4 feet-tall by 5 feet-wide
ones even better. The bottom of the pile should be exposed
to the earth, and the top should be covered with black
plastic or a waterproof tarp to protect it from extreme
rain or drying sun. Contained piles should also have enough
open spaces in their sides to allow for good air
Kosher and Nonkosher Organic Compost Materials
So many types of organic matter can be composted that it's
almost easier to list what shouldn't be put in a
compost pile. Here's a partial list of what not to use:
Cat feces. While almost every other kind of animal
manure makes an excellent compost ingredient, cat feces can
contain a parasite ( Toxoplasma gondii )
or roundworm ( Toxocara catty ). Either
of these organisms can spread serious disease to pregnant
women, unborn babies, and children.
Grease and fat. OK in small amounts, but too much
will clog up the composting process.
Coal, coal ashes, and barbecue briquettes. These
have overly high amounts of iron and sulfur (and who knows
what else in the briquettes).
Diseased plant matter. Actually, you can place
diseased plants in the center of a compost pile that will
be prepared in the hot method — where temperatures
reach a pathogen-killing 140 degrees Fahrenheit. Otherwise, burn them
Polyester, plastics, and other synthetics. They
just don't rot.
Urban floor sweepings. In high-traffic areas,
these can contain as much as 500 parts per million of lead.
Food preserved with BHT. Recent research has shown
that even very small amounts of this antioxidant can alter
plant growth profoundly.
Overly bulky or hard material. Cornstalks,
sunflower stalks, nutshells, sticks thicker than a pencil,
large bones, and oyster and clam shells should be shredded
or pulverized before composting. If you can't do that, put
them in a long-range pile of their own or burn what you can
and add the ashes.
Sludge. Commercially reprocessed sludge is an
increasingly popular soil amendment and is almost certainly
pathogen-free, but I'm concerned about the heavy metals and
insecticides it may contain.
And what are good compost makings? Well, for starters, how
Plant residues (preferably nonsprayed), such as
kitchen and garden wastes, weeds, grass clippings, leaves
(go light on those from eucalyptuses, walnuts, and
evergreens), straw, hay, hedge clippings, seaweed, aquatic
plants, and green manure crops.
Commercial wastes, such as buckwheat hulls, rice
hulls, molasses-making residue, spent hops,
fruit-processing wastes, commercial fishing scraps, lake
dredgings, sawdust, feathers, wood ashes (in moderation),
utility-company tree trimmings, and vegetable or dairy
wastes from grocery stores.
Home wastes, like eggshells, hair, wool scraps,
Manures from horses, fowl, cows, pigs, sheep, etc.
These are even better if they're mixed with straw (i.e.,
used stall bedding).
The Six Essentials for Home Composting
Once you've assembled lots of appropriate organic matter
from the "compost pile shopping list" above, you're just
about ready to start cooking. The funny thing, though, is
there is no one way to make compost —
indeed, there are almost as many methods as there are
experts to advocate them.
It's like baking bread: There are thousands of different
recipes, but all of them have in common some basic
practices and vital main ingredients. So before you build
that long-awaited heap, let's quickly review the six
essentials of successful composting:
Nitrogen. For a compost to cook properly and to
have maximum value for plants, it needs nitrogen, the
leaf-growth-promoting element. Good sources of N are pig,
chicken, sheep, horse, and cow manure (ranked in descending
amounts of nitrogen) . . . fresh green plant waste
(especially legumes) . . . kitchen wastes . . . blood,
bone, cottonseed, hoof, horn, and alfalfa meals (readily
available from garden supply centers, but somewhat costly)
. . . and urine. This last nitrogen source may be animal or
— if you're not made squeamish by the thought —
human. Indeed, "household liquid activator," as human urine
has been dubbed, is practically sterile, available to
everyone, and a perfect nitrogenous compost catalyst. (You
can collect it in a lidded bucket — a chamber pot,
our forebears called it — and dilute it with water,
then add it once the pile is hot. A week's urine
should provide plenty of N for a good-sized pile.)
Carbon. The vast bulk of any compost pile should
be carbonaceous material: dried leaves, hay, straw,
partially dried garden gleanings, shredded stalks —
almost any dried organic matter. This is the key
humus-building material and the substance that binds
nitrogen (an otherwise ephemeral element) into the compost.
Air. Although organic matter can decay
anaerobically (without oxygen), it will do so much quicker,
retain more nutrient value, and — for that matter
— cook with much less stink if it composts
aerobically (with oxygen). To provide good airflow to a
pile, you should, if possible, place thick, hollow material
like cornstalks and sunflower stalks at the bottom of a
pile. Also, be sure that any compost bins or pens have
Once the pile is built, you can try poking holes in
numerous places with poles or branches to increase aeration
— although I've never noticed that this technique
made much difference. You can try using a "compost
aerator," a pole with a flap like a toggle bolt that opens
up when you pull it up out of your pile (available from
garden supply companies). I've never used one myself. Or
you can just break down and use the age-old method of
adding oxygen to a pile: turning it. Periodically, take a
garden fork and turn the pile — upside down and
inside out — over on an adjacent spot.
Water. A compost pile needs moisture to cure.
However, too much water will drown out the air and stop the
process. The ideal heap, then, is damp but not soggy.
Mass. As pointed out earlier, a compost pile
needs to have at least a cubic yard of bulk to heat up
properly. And the bigger the better — up to a point.
A pile can hardly be too long or wide, but one that is
too tall (say over five feet high) may mash down
and squeeze out air.
Beneficial microorganisms. These are the guys who
actually do all the work. You can buy beneficial bacteria
packets to inoculate your compost, but these little fellows
are pretty much everywhere and will thrive if you give them
an environment they like. One simple way to inoculate your
piles for free is to occasionally sprinkle some good garden
soil — or compost from a previous pile — on the
one you're constructing.
If your pile doesn't heat up, something's wrong.
Putting It All Together
Now that you know the six essential ingredients of a good
compost pile, you need to know how to combine them. The
basic technique is simply to alternate layers of
nitrogenous and carbonaceous materials. If your pile is all
carbon or all nitrogen, your bacteria's diet will be too
far out of whack for them to do their job.
The ideal carbon-to-nitrogen ratio is about 25 to 1, but
you'd need all sorts of time and charts to figure out how
to achieve that precise ratio out of the materials you may
have on hand. It's easier — and perfectly effective
— to just take some ingredients from the carbon list
and some from the nitrogen list and layer them,
experimenting with proportions until you find what works
In a nutshell, then: 1) Lay down some stalky material,
preferably on bare soil you have forked up some to allow
easier passage for bacteria and earthworms. 2) Fork on a
layer of carbonaceous material. 3) Fork on a layer of
nitrogenous matter. Each layer — N or C —
should be about two to eight inches thick. And fluff it up
as you add it to promote airflow. 4) Repeat steps 2 and 3
until you've finished building your pile. Sprinkle on a
spadeful or two of soil or cured compost occasionally, and
if your materials seem dry, spray on some water
periodically as you work. 5) Cover the pile with a
waterproof tarp to protect it.
I mentioned that you'll have to experiment to find the best
ratio of materials for you. One of my "old reliable"
combinations, if you'd like to try it, is alternating in a
5-5-2 pattern: a five-inch layer of green matter, a
five-inch layer of dry matter, and a two-inch layer of
manure. But — contrary to some opinions — good
compost piles can be made with all vegetative matter and
no manure. Just make sure you have enough nitrogen
(here's where something like blood meal or human urine is
If It Didn't Work
If all goes well, in about four or five days the interior
of your compost pile should have heated up. Indeed, before
long a hand poked inside the heap will get uncomfortably
If that happens, congratulations! Your compost is cooking!
If your pile doesn't heat up, something's wrong. First
check to see if the pile is too wet or too
dry. If it's too soggy, turn it, adding more dry
material as you do. If it's too dry, wet it.
Assuming the pile is properly moistened and isn't too
compressed for good air circulation, your problem is that
the compost mixture needs more nitrogen . Turn the
pile, incorporating more nitrogenous material as you do so.
You may have a different problem — namely, the cooking
mound will smell like ammonia. In that case, you've got
too much nitrogen. So turn the pile, adding more
Fast, Medium, or Slow Composting
There's one last step to making compost: turning the pile.
And here you have some choices. If you want to get your
compost quickly, you'll turn the pile every time its most
intense heat (104 degrees to 170 degrees Fahrenheit) starts to drop —
about every three to five days. That will add more oxygen
and kick up the process. Keep that up and you should have
finished compost in two months or less. If all the
ingredients have been finely shredded, thinly layered, and
turned every three days, it's even possible to make usable
compost in two weeks!
If you want your compost in a medium amount of time, turn
the pile approximately six weeks after you make it and
again six weeks later. Your humus should be ready four to
six months after you started it.
And if you're long on patience and short on turning time,
just leave the mound alone. Such a slow pile should be
ready to use after a year (or even a little longer).
Time is not the only consideration here — there are
raging debates about whether "quick" or "slow" compost is
better. Since quick-cured piles get well above the
pathogen-killing temperature of 140 degrees Fahrenheit, they're the way
to go if you want to compost diseased materials (or kill
On the other hand, slow-pile advocates claim that
cold-cured compost (which cooks at around 100 degrees Fahrenheit)
retains more nutrients.
So relax, dig in, and don't be afraid to experiment.
Whichever way you compost, you'll be making the best soil
builder your garden could have. You'll also be
participating in the light cycle that connects all life on
this planet-plant, animal, and even human. As Leandre
Poisson has pointed out, we ourselves are "light's ultimate
SUPER COMPOST BOOKS
The Rodale Guide to Composting, $14.95 postpaid
from Rodale Press, Emmaus, PA.
Fertility Without Fertilizers, by Lawrence D.
Hills, Henry Doubleday Research Associates. Out of print.
Let It Rot, by Stu Campbell, $7.95 postpaid from
Storey Communications, Inc., Pownal, VT.