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Making and using compost at The Rodale
Institute farm By Laura Sayre
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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 year-round. "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.
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. (The Field 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 further investigation."
"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."
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