August 10, 2006: Steve Groff and family run Cedar
Meadows Farm, 200 acres of mixed vegetables, grain and seed crops
situated in the heart of Lancaster County, Pennsylvania. The bucolic
setting is arguably one of the most beautiful farming regions in
the country. It’s also a laboratory of sorts. Groff is a pioneer
of sustainable agriculture techniques, specifically no-till—which
he’s been practicing since the 1980s—and the use of
cover crops to add fertility, protect and improve the soil, reduce
chemical use and enhance water quality. Pennsylvania State University
grad students and professors are no strangers to Groff’s farm,
nor are the researchers here at The Rodale Institute.
The Cedar Meadow Farms Field Day July 14 is one of many that have
taken place on Groff’s land over the years, this one representing
a collaborative effort between Groff, Penn State, The Rodale Institute,
and the Pennsylvania Association for Sustainable Agriculture. The
theme was “Integrating no-till practices and cover crop use
to build soil quality and manage pests.”
Groff utilizes a permanent cover cropping system that incorporates
no-till, cover crops and effective crop rotation strategies. Several
concurrent workshops July 14 drew from research that’s taken
place at Cedar Meadows Farm, with highlights including how cover
crops and crop residues encourage soil microbial activity, how they
enhance beneficial insect populations, and how cash crops respond
to different cover-cropping strategies.
Three program tracks with a total of seven possible workshops encompassed
the field day. This report centers on four of those tracks.
“It’s not a perfect farm, and we’re continuing
to learn,” Groff told the crowd of about 400, sharing his
own vision “to find that perfect balance between environmental
stewardship and economic profitability” before sending us
all off in various directions across his farm.
Cover crop selection
Timing is a critical as type and variety selection, all the presenters
agreed, and the chosen cover has to be an appropriate match for
the region, the cropping method, and the cash crop that follows.
Groff himself has been working on an early maturing hairy vetch
that can be killed up to a week sooner than traditional varieties,
thus allowing for earlier planting into the thick living mulch the
vetch forms once it’s rolled down (hairy vetch also fixes
nitrogen, most optimally if seed is inoculated before planting).
But roll down hairy vetch too early and it comes right back. Optimum
roll-down time is when at least 75 to 90 percent of the crop has
begun to flower, because the plants “think” they have
done their job and will no longer struggle to reproduce.
Groff is also growing forage radishes (diakon) as a cover crop
and is producing seed for other farmers. He offered that a farmer
can seed this crop—which biodrills deeply into the soil; like
a carrot, only bigger—for about $20-$25 an acre. Besides breaking
up the soil, he said, the radishes express some allelopathy, that
is, they secrete chemicals that keep other plants around them—namely
“I believe the soil is meant to be covered,” Groff
told the workshop crowd gathered around a table of various potted
cover-crop samples. He cited a number of reasons for mixing various
cover crop types. For instance, he mixes vetch with rye partially
because the rye keeps the vetch off the ground, making it easier
to harvest the vetch seed.
Hairy vetch releases nitrogen on a curve, Groff explained, so it’s
critical to time the planting of a heavy feeder such as corn to
match the nutrient cycling of the cover. For Groff, that’s
around June 15. While different varieties of cover crops have varying
tolerance to winter, Groff advised, it’s a good idea to get
even the most hardy ones into the ground at least by the second
week of October (Groff farms in USDA Cold Hardiness Zone 6).
Still riding the hairy vetch train, Rodale Institute agronomist
Dave Wilson said that a 15-30 pound seeding per acre of the popular
cover crop can deliver up to 9,000 pounds of dry biomass and more
than 200 pounds of nitrogen (the amount will vary from year to year
depending on rainfall and growing degree days). “We use it
in our organic farming system for natural weed suppression, and
it gives us all our nitrogen for our corn,” Wilson said, explaining
that the vetch and corn residue are incorporated into the soil through
tillage once the corn has been harvested.
One big challenge of cover crops as living mulches, Groff said,
is planting into them. Another, he said, is that they are typically
aggressive. “When you plant vetch on your farm, you will have
vetch on your farm.” About 3 to 5 percent of hairy vetch seed
won’t germinate the first year, he said, yet it will remain
viable up to five years. “And you will see one seed in your
wheat, because hairy vetch seed is shiny black.”
Wilson offered other effective cover crop combination examples
of red clover, ladino clover or berseem clover frost seeded into
winter wheat. “If you want nitrogen, you grow legumes,”
he said. Non-legumes can act as a nurse crop, provide biomass and
sequester excess nitrogen after your cash crop. “Rye sucks
it up,” Wilson offered, explaining that this captured nitrogen
becomes available to crops the following year after the rye has
been incorporated into the soil. “Rye tends to dry the soil
out in the spring if you let it grow too long” and may be
a problem in a dry year, he added.
When combining covers, you’ve got to be aware of their habits,
offered Groff. “People won’t believe it unless they
see it, but radishes will outgrow anything you have,” he said,
including oats and rye. So instead of mixing and broadcasting seed,
he said, he alternates rows when the desire is to pull in the benefits
of a variety of cover crop species that includes the aggressive
Sometimes, Groff said, cover crops behave differently when matched
together. “I don’t know why, but rye kills [more easily]
when it’s mixed with vetch,” he said.
Reiterating that choosing the right cover crop or mix is a matter
of matching the right cover to the right crop, timing your plantings
in a way that the cover and cash crops best complement each other,
and having specific goals in mind, Groff said; “You have to
look at the whole program and decide what it is you’re trying
Soil quality and beneficial organisms
Mark Goodson, Penn State Extension educator led this session with
a discussion about the glue that binds…soil particles, that
is. “Glomalin is the Superglue of the soil,” he told
the gathered crowd of the substance—a byproduct of the interaction
between arbuscular mycorrhizae fungi and plant roots—discovered
only a decade ago. This intense binding leads to aggregate stability,
he said, opening up pore spaces for roots to grow and for water,
air and nutrients to travel freely.
Carbon dating tells us that glomalin, a combined sugar and protein,
is so stable that it lasts up to 42 years, Goodson said.
In the symbiotic relationship between mycorrhizae and plant roots,
he explained, the plant feeds the fungi sugar and the fungi in turn
provide the plant with nutrients (nitrogen). All plants—with
the exception of some of the brassicas—have some sort of relationship
with mycorrhiza fungi, Goodson said, which attach to roots and grow
long, thin hyphae, threadlike filaments that reach further into
the soil (up to 18 feet) gathering water and nutrients. These fragile
hyphae make glomalin to protect themselves, then decay and slough
off about every 10 days. “That glomalin goes into the soil
and forms these tight aggregates,” Goodson explained.
“One-half to one-third of the organic material in the soil
is this glomalin,” Goodson said. These levels drop with increased
tillage, he said, thus degrading the tilth, or structure, of the
soil and the ability for infiltration.
Next up, Randa Jabbour and Meredith Murray, both graduate students
in Penn State’s Department of Ecology, introduced the concept
of the soil food web. “Soil is alive,” Jabbour said,
ratting of a laundry list of underground inhabitants that include
beneficial fungi and bacteria, nematodes, worms, insects, spiders
Murray then presented a “beetle box” that held preserved
samples of dozens of the little insects in a range of sizes with
a host of different functions. “This one specializes in eating
snails,” Jabbour explained.
At Cedar Meadows Farm, Murray, Jabbour and their colleagues study
weed seed predation by ground beetles. Murray explained how researchers
use pitfalls—homemade beetle traps fashioned from plastic
soda bottles and baited with antifreeze—to catch beetles within
a given area. By collecting beetles and counting seed that has been
placed in a given cover-cropped area over a 14-day period, researchers
get a pretty good idea of weed-seed-predation rates. At Cedar Meadows
Farm, they’ve calculated that to be about 84 percent, with
more of the weed-seed removal attributed to vertebrates than invertebrates.
“Once rodents find a spot with a large amount of seed, they
keep coming back until those seeds are gone,” Murray said.
“And they’ll tell all their friends.” (See our
weed-control service: Mice for more on weed seed predation by
One important bit of information learned through this study is
that certain cover crops and management practices encourage these
important weed-seed predators by offering favorable habitat. “The
highest seed predation was in cropping systems that formed a nice
canopy cover,” Murray said. “It gives [weed-seed eaters]
protection from predators.”
As for cropping systems, Murray said there wasn’t a lot of
difference in beetle populations in spring but that in fall—when
beetles were most active—they thrived more in areas were tilling
was minimal or nonexistent. If you can encourage habitat and map
a weed-seed-eating insect’s life cycle with the prevalence
of weed seed on the soil surface, she said, “You’re
going to see a larger decrease in certain weeds the following year.”
Ecological weed management
Following a scrumptious chicken barbeque prepared by Groff’s
church, those of us on Track 1 tromped into the blazing heat behind
William S. Curran, PhD, professor of weed science at Penn State.
Ecologically based weed management is about combining many “little
hammers” like allelopathy, encouraging weed seed predation
and implementing cover cropping strategies to take the place of
the “big hammers” like pesticides and tillage, he said.
Walking into experimental corn plots—some planted in cover
crops and some not—Dr. Curran identified several typical weeds,
including lambsquarter, redroot pigweed and foxtail. “When
you’re managing cover crops properly, you will have lots of
biomass,” he said. “The key is in trying to catch the
weed-suppressive properties of the cover crops.” These properties
- Creating a physical barrier.
- Reduction of light penetration.
Curran suggested a goal of at least 5,000 pounds of dry matter
per acre for adequate weed suppression. While hairy vetch is a popular
cover for its ability to deliver nitrogen, Curran said it’s
a succulent and so tends to disappear quickly. Mixing in cereal
rye, he said, combines for a more persistent cover that offers better
weed control over time. “You can manage weeds with the residue,”
he said, adding that the most critical time for controlling weeds
in corn is at four or five weeks.
“When do weeds wake up?” This was the question posed
by Andy Hulting, a weed ecologist at Penn State, and he brandished
a poster bearing the same theme. “Typically, you see more
weeds in early planted corn than in late-planted corn.”
Timing is everything, he said. “You want to wait to plant
to allow the weeds to come up so you can manage them.”
Hulting led us to four 10’ x 80’ plots of corn planted
the same day using various cover cropping strategies. “The
weed population decreases as you go down the hill,” he said,
pointing out that as cover crop biomass decreased, weed pressure
“The timing of your weed management does matter.” Certain
weeds are common in spring, he said; “a whole suite of different
weeds become a problem later in the summer.” Questions you
have to ask yourself, he said, include:
- What weeds are a problem?
- When is the best time to think about managing them?
- What is the optimum time for planting considering the above?
Cover crops and rollers
“A number of years ago, we began looking at how we could
reduce tillage on our organic farm,” said Rodale Institute
farm manager Jeff Moyer. “We’ve seen farmers who reduce
tillage use more herbicides. If you reduce something, you usually
have to increase something else.”
Since increasing herbicides was not an option for organic production,
Moyer said, the farm increased its intensive management of cover
crops. Then it increased its technology, rolling down cover crops
into a living mulch and planting into them.
“We started out with a Buffalo stalk chopper, which knocks
down and chops corn stalks. It will kill most of the cover crop
as long as it’s a winter annual. We’re trying to work
with cover crops that normally would want to die.”
Discovering that some cover crops are tenacious—particularly
when a rather easy-to-kill crop such as hairy vetch is mixed with
a tougher customer like cereal rye—Moyer and farmer neighbor
John Brubaker did what any good farmer would do; they designed a
Protruding fins in the new roller design cut off the vascular system
of the plants by crimping stems every seven inches, and the unit
can be filled with water to regulate down pressure. Since the fins
are mounted at an angle rather than 90 degrees, they don’t
pull the plants out of the ground and disturb the soil, as the stalk
chopper did. The elegant-yet-simple design also sports two bearings
instead of 16.
And the front-mounted roller allows for coordinated roll-down and
seeding in one pass, also saving time and energy. “All you
have to do is go back and harvest,” said Moyer. “That’s
just two trips to the field.” (Read more about the roller
and our latest research surrounding the tool on our No-Till
Finally, Rodale Institute agronomist Dave Wilson took to the field
once more to wrap up the day with a talk about how our farm utilizes
cover crops in conjunction with limited tillage in an organic system.
This season, he said, in the aboveground biomass produced by the
hairy vetch there was a whopping 245 pounds of nitrogen per acre,
plenty of fertility in which to plant corn. The vetch also acts
as a weed suppressor. (Later, Wilson explained how we learned the
hard way that vetch can create a hospitable environment for “bad
critters” like cutworms as well as good ones like the weed-seed-foraging
beetles discussed above. We had to replant our corn when an earlier
planting was decimated overnight. Again, Wilson stressed, it’s
all about careful observation and timing.)
One of the biggest challenges of utilizing a cover crop as a living
mulch is direct-seeding into it, because of the thickness of the
mat, Wilson said, offering that for vegetable crops you would need
to use a no-till transplanter to be successful.
The hairy vetch at The Rodale Institute, seeded at 25 to 30 pounds
per acre, also attracts an abundance of pollinators and other beneficial
insects, Wilson said, reminding everyone that the biomass aboveground
is complemented by belowground biomass, where the root zone creates
the additional benefit of contributing to a robust soil food web.
A big difference Wilson noted between no-till and cultivated corn
systems is the cultivating action between rows actually throws soil
against the corn stalk and buries emerging weed plants, so the weeds
that grow in the organic tilled system are in the row with the corn
or soybeans. In the organic no-till system, there are more weeds
between the rows of corn and soybeans and fewer weeds in the row
with the corn or soybean plants, he explained, so the weed-to-crop
proximity is different in the two systems.
Wilson also noted a few trick and tips when working with different
cover crops utilized for organic no-till soybeans. “If you
roll rye perpendicular to the direction of the drilled small grains
you get better cover than if you roll it in the same direction of
the drilled rolls.” Barley and wheat can be used as cover
crops but won’t deliver as much biomass as rye. Spring oats,
planted in the fall with hairy vetch, offer a nice nurse crop (protective
canopy) for the vetch, which can be hard to get started and will
winter kill if there’s not enough growth on it before frost
arrives. “The oats sequester some of the free nitrates—the
nitrogen in the soil—and then they winter kill.”
Wilson also counseled that, for reasons of adaptability, it’s
better to get seed produced in the region where it is to be grown.
Like Groff, he stated that you have to consider many factors—including
economics, region, and desired function—when choosing your
cover or mix.
“Hairy vetch is more expensive than crimson clover,”
Wilson said, adding that as you move north, crimson clover doesn’t
overwinter as well or produce as much biomass as vetch does.
Organic no-till differs from conventional no-till in a variety
of ways other than the absence of pesticides, Wilson said, and the
system presents particular challenges. “In most conventional
no-till systems, you’re not normally dealing with 9,000 pounds
of dry cover crop biomass,” he said. “You’re normally
cutting into a mat of crop stubble or a killed sod or hay field.”
“We need at least four- to five-thousand pounds of cover
crop dry matter per acre for effective weed suppression; the weed-suppression
aspect is a big deal for us in organic no-till.”
Whereas conventional no-till is often continuous no-till, he said,
organic no-till is rotational no till. Still, Wilson said, conventional
no-till farmers have found a way to reduce pesticide use to 1/16
or even 1/32. That, he said, reduces the farmers’ input costs,
and reducing herbicides is good for the environment and the farmers'