| Cedar Meadows Farm
Field Day By Dan Sullivan |
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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 weeds—from growing.
“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 forage radish. 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 to do.” 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 and mites.
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 story Free weed-control service: Mice for more on weed seed predation by rodents.) 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 include:
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 increased. “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:
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 better solution.
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 Plus Page.) 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'
well-being. |
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