August 17, 2004: August has arrived, and in
addition to baling straw and making hay and establishing cover
crops and prepping ground for wheat and barley, at The Rodale
Institute® that means one thing: it's time to spread compost.
For most of the past couple of weeks, Rodale farm interns
John Chandler, Emily Gallagher, Teresa Cuperus, Tianna DuPont,
and Kelly Grube were taking turns using the bucket loader
to fill the manure spreaders and shuttling out to the fields
to spread a thin layer—12-15 tons per acre—of
the good black stuff on all the ground that was harvested
last month for oats.
It hasn't always been this way. Farm manager Jeff Moyer used
to follow conventional wisdom by putting down compost before
corn, in the spring. But a number of factors led him to reevaluate
this practice. First, he suspected that the wheat—the
last crop in his arable rotation—wasn't getting enough
residual fertility. Second, when he started experimenting
with planting no-till corn into a rolled-down cover crop,
adding compost at the same time became impossible. That in
turn made him realize that with the corn following either
vetch or a hay plow-down, additional nitrogen from compost
wasn't even necessary. He's since decided that August is a
better time to spread compost anyway, because the ground tends
to be drier, and he's got more time than he does in the spring.
Now Moyer's seven- to nine-year rotation looks roughly like
this: oats or rye (followed by compost), winter wheat, two
to four years of alfalfa/red clover/timothy hay (underseeded
in the wheat), corn (followed by a rye cover), oats (sometimes
followed by compost), soybeans. Sometimes, instead of a multi-year
hayfield, Moyer will just use hairy vetch or a vetch/oats
mix as a cover crop between the summer wheat harvest and corn
planting the following spring. He puts down compost between
oats and soybeans if he bales most of the oat straw, as he
did this year because he had a good market for it. On
average, any given field at TRI receives compost just once
in five years. Even though corn is a notoriously
heavy feeder, Moyer says it's easy to give it enough fertility
with legumes alone.
In other words, while Moyer is a tireless advocate of composting
as "food for the soil," he knows it's a material
to be used judiciously. "Compost is a valuable resource,"
he emphasizes. "If you've got too much, you're probably
better off selling it than over-applying it." As The
Rodale Institute's Compost Utilization Trial—a long-term
study comparing the costs and benefits of different types
of composts—demonstrated, you can use too much. In most
cases, compost shouldn't be used to supply all crop nutrient
requirements because the nutrient balance will be thrown off.
"If you're using compost for all your nitrogen needs,
your phosphorous levels are going to go through the roof,"
Jeff points out. "I think of compost as a microbiological
feed source for the soil more than as a primary source of
fertility for the crops."
Getting started in on-farm composting
"A lot of people think that only farmers with livestock
can make their own compost," says Moyer. "It does
make life easier if you have critters," he acknowledges,
but it's by no means essential. Over the past twenty years
or so many U.S. states (including Pennsylvania) have banned
the disposal of yard waste in landfills, forcing larger municipalities
to collect leaves and yard waste separately. While some counties
and local governments operate their own public composting
facilities for that purpose, many others are more than happy
to deliver the material to local farmers.
The Rodale farm has worked with a variety of off-farm sources
and materials over the years. Currently, Moyer is making compost
out of municipal leaves, grass clippings, and horse manure.
The leaves come from the city of Allentown and the town of
Topton; both leaves and grass clippings from Lower Macungie
Township, also nearby; the horse manure comes from custom
haulers who collect it from area horse farms. The leaves arrive
in the late fall and early winter as municipalities are clearing
their streets—in 2003, TRI received some 500 truckloads.
This suits Moyer because the colder the ground is, the easier
it is for the trucks to get in and out. Grass clippings arrive
throughout the mowing season, and horse manure is delivered
"We try to make our composting system as uncomplicated
as possible," explains Moyer. "First of all, it's
a free system. We don't charge for tipping, nor do we pay
for materials." This simplifies the paper trail, and
it also gives you a greater ability to make demands about
the quality of what you get. Second, Moyer tries to receive
materials exclusively from custom haulers, not from private
individuals, and to keep the total number of suppliers to
a minimum. This makes it easier to keep track of who's bringing
how much of what, and when.
Another way to simplify your on-farm composting system is
to site your compost piles close to the road, or at least
in plain view of the road, so that delivery trucks can see
where they need to go. The Rodale farm has two composting
areas, one on each side of the main road that bisects the
property, making it easier to move the finished compost to
different parts of the farm.
Moyer cautions that farmers need to be aware of state and
local regulations before they start receiving materials from
off-farm. Until recently, the choice in Pennsylvania was between
getting a permit and getting permission: the permit to run
an on-site composting operation cost thousands of dollars
and was the same as a permit to operate a landfill; but farmers
also had the option of simply getting a letter from the PA
Department of Environmental Protection granting permission
to receive yard waste materials (this is what TRI has). In
2002, PDEP introduced an on-farm composting permit which is
more affordable and allows farmers to receive source-separated
food waste from grocery stores and cafeterias in addition
to yard waste. (See Grocery
Store to Farm for more on this option.)
In either case, careful site selection is an important part
of establishing an on-farm composting operation, and farmers
should be prepared to receive a visit from a state inspector.
The primary concern is to minimize run-off and to protect
natural water courses. At the Rodale farm, Moyer maintains
permanent grass biofilters (cut once a year for hay) down-slope
from the composting sites for this reason.
TRI sells some its compost to staff and the general public
at $5 per cubic foot or $35 per cubic yard. For most farm
situations, Moyer recommends marketing compost as a 'soil
amendment,' not as a 'fertilizer,' because if you market it
as a fertilizer you are required by law to provide a guaranteed
nutrient analysis. While it's a good idea to get the nutrient
profile of your compost analyzed, unless making and selling
compost is your primary business you probably don't want make
that guarantee. Here in Pennsylvania a permit to sell soil
amendments is required by the PA Department of Agriculture—a
relatively simple process that involves paying a fee and keeping
track of how much is sold.
Since the clopyralid scare of a few years ago, of course,
sourcing compost materials off-farm raises concerns about
possible contamination. (Clopyralid is a broad-leaf herbicide,
sometimes used on lawns, that has been shown to survive the
composting process.) The Rodale farm has yet to experience
any problems (knock on wood), but as a precaution, Moyer and
his staff never put grass clippings into the piles in the
farm's lower composting area, which serves the Institute's
greenhouses as well as the lower fields. Effects from clopyralid
and other potential contaminants are much more likely to show
up in a potting mix than from field-scale applications.
If you can't buy the tool, build it
Once you've got your bulk materials, of course, the challenge
is how to mix and turn them to facilitate the composting process.
In the early years of compost production at the Rodale farm,
Moyer and others mixed materials in one of two ways: either
by using a front-end loader to load them into a manure spreader
and then inching the spreader along to create a windrow; or
simply by using the front-end loader to stir and shift the
piles. "That's a great job for teaching teenagers how
to use a front-end loader," observes Jeff of the latter
method. "You can put 'em out there and let them practice
all day long. But otherwise, it's not very efficient."
The manure-spreader-mixing method is also slow, and so a
decade ago Moyer and his team decided they wanted to either
buy or build a dedicated compost turning machine. "We
went out and looked at the various examples out there at the
time," recalls Jeff. "And basically there were three
types. There were farmer-built units, there were commercial
units priced and marketed for farmers, and there were commercial
units priced and marketed for municipal facilities."
These three categories still pretty much cover the range
of units out there, says Moyer, and all three types have disadvantages.
Most farmer-built units are tractor-propelled and PTO-powered,
which generally means they're underpowered for turning tons
of dense material. Commercial units marketed for municipalities
can cost hundreds of thousands of dollars—way beyond
farmers' budgets—while commercial units marketed for
farmers tend to be small, designed to handle piles only about
three feet high by six feet wide.
So the Rodale farm crew decided to build their own. To be
worth the effort, the machine's design needed to answer all
the shortcomings Moyer had identified in his survey of existing
models: it had to be inexpensive, able to handle large windrows,
and have plenty of power. Ideally, Moyer thought, it should
also be self-propelled and fully transportable, at least around
the back roads in the neighborhood of the farm. As Jeff puts
it, "We thought it would be interesting for a farmer
to own a transportable compost turner, which could potentially
be used for a side business by a son or a daughter, like custom
haybining." On a single farm producing compost primarily
for its own use, after all, a compost turner is going to spend
a lot of time sitting idle.
Working with the Institute's ingenious Mennonite neighbor,
John Brubaker, Moyer and his staff developed a design built
around a dump truck with a burnt-out cab, sourced from a local
salvage yard. (Brubaker is an expert welder and has worked
with the Institute on a number of projects over the years,
including, most recently, the front-mounted cover-crop roller
in use for our organic no-till trials. Click
here for more on that project.) They removed the dump
truck's bed and what remained of its cab (eventually selling
them back to the salvager) and kept the engine, transmission,
and frame rails. Additional steel, motors, and valves were
purchased from military surplus and salvage yards.
The key innovation in the design of the turner was to use
the truck's 320-horsepower, 8-cylinder engine and 10-speed
transmission to power the machine's pile-turning auger, and
then to add a hydraulic system with hydrostatic drive to power
the wheels. The hydrostatic drive allows the operator to adjust
the forward motion of the machine according to the density
of the pile, and to move very slowly through compacted material.
To make the unit transportable, the front and rear wheel-platforms
pivot 90 degrees with respect to the 16-foot open auger housing,
situated between them. In transport mode, the machine is a
9-foot wide, 35-foot long truck with the auger for its body.
In pile-turning mode, it's a 35-foot wide, 9-foot long self-propelled
implement which straddles the compost windrow while the operator
stands on the platform directly to one side. The machine can
handle a pile up to 6 feet high by 12 feet wide.
Another critical aspect of the turner's design was figuring
out how to shape and configure the auger's teeth to optimize
the movement of material within the pile. Ideally, material
should move along the auger toward the center of the windrow,
be forced up from the center to the top, and then fall out
down the sides of the windrow. The team contacted an existing
manufacturer of compost turners for advice on shaping the
teeth to do this—to their surprise, the manufacturer
was happy to give them the necessary specifications.
In the end, the machine cost about $20,000 to build, evenly
divided between parts and labor, with the labor charged at
$20 an hour. "Even if you doubled that to account for
inflation, forty thousand dollars is not the kind of figure
that scares large-scale farmers," Moyer notes. It's a
reasonable amount for a machine of its kind; and although
it was a custom design, any farmer with a good shop and good
metal-working skills should be able to build something similar
for the same kind of price tag.
After a decade of working with the massive machine, Moyer
and the farm operations crew say they're fully satisfied with
how it came out. "It's kind of loud, but some people
consider that a plus," Jeff jokes. "The only things
we would change [if we built it again] are very minor things—there's
a body panel on one side, for instance, that sometimes gets
bent as it moves through the pile; it needs to be angled differently."
Aside from replacing a few teeth on the auger—they are
bolted on individually for that reason—the machine has
required only routine maintenance.
more on the machine, see the slideshow:
A compost windrow-turner
made to order
The compost cure
Moyer and his staff still use the front-end loader to tidy
up the windrows, if necessary, after the bulk materials have
been delivered. Then they power up the compost turner. "We
tend to turn [the material] a lot when we first get it, maybe
four times in a month," Jeff explains; "then we
might let it sit for six months. The more you turn it, of
course, the quicker you can finish it and therefore the more
you can produce on a given area." In Moyer's farm management
calculus, however, the extra labor of turning is not worth
the potential for increased compost production. "I have
enough room, and enough time to let it sit there; what I don't
have is the labor." Each farm needs to determine its
own balance between space, supply, work force, and output.
Guide to On-Farm Composting includes equations for calculating
the area needed for composting different volumes of material
over different periods of time.)
In their early years of making compost, Moyer and the TRI
farm staff did lots of temperature monitoring and other testing
to evaluate their compost-making process. Now that they have
their method down, however, this is not usually necessary.
After six months or a year, the windrows are combined—
because of the volume reduction that accompanies composting,
two or three original windrows can be pushed together into
one—and left to cure. Curing is the final stage in the
composting process, and ensures that the nutrients have stabilized
and any naturally-occurring phytotoxins have had time to break
down. By the time it gets spread, TRI's compost has generally
been on the property for between 18 and 20 months. The best,
most mature compost goes to the greenhouse, because the higher
proportions of compost used in potting mixes make the potential
effects of immature compost more serious.
Another maintenance chore associated with composting is staying
on top of the weeds that can grow up on the older piles. Weed
seeds in the piles should be killed by the high temperatures,
but more will blow in and germinate. Like most farmers, Moyer
tries to find the time to knock these down before they set
seed. You can buy windrow covers made of wool or permeable
synthetic fibers, but Moyer believes they are only likely
to be cost effective if you are in the business of selling
compost. "Last year we experimented with throwing some
cheap clover seed on the cured piles for a green cover, to
control the weeds, control run-off, and take up the excess
water," Jeff notes. "I think that idea is worth
"I think more farmers could be making compost for their
own use or for sale," says Jeff, whether they keep livestock
or not. "Some farmers say composting is an extra step
versus just spreading manure directly onto the fields,"
he notes. "But it all depends on when you have the extra
time." If you're not spreading directly from the barn
to the fields, for instance, then you can clean out the barn
when the weather won't allow you to spread.
"As farmers, we need to reevaluate how we utilize all
of our resources," Jeff observes. The essence of composting
is to take waste products—whether they're livestock
manures or municipal yard wastes—and transform them
into a valuable material. It reduces the overall volume, which
saves handling time and expense; it eliminates offensive odors;
as a soil amendment, it contributes organic matter as well
as nutrients; it supplies those nutrients in a more stable,
less leachable form than raw manures; and it creates a saleable
product out of disposal problem.
"Look at it this way," concludes Jeff. "If
you spill a load of manure in the center of town, you've got
a toxic waste problem on your hands. If you spill a load of
compost in the center of town, all the neighbors will come
out to help carry it away."