Down the Drain: liquefied manure and drainage tile
By DAVID GREEN
When Frank Gibbs forces smoke through an agricultural field tile, the results grab the attention of farmers.
Gibbs, a soil scientist with the Ohio Natural Resources Conservation Service, places a smoke bomb into a tile line, then attaches a blower to push the smoke up into the field.
It’s only a matter of minutes before smoke begins rising up from the soil throughout the field, clearly delineating the position of tile. If farmers hold any doubt about the direct connection between the surface of a field and the tile line buried several feet below, it’s quickly dispelled.
It doesn’t always take a smoke test to see the connection. The Michigan Department of Environmental Quality (DEQ) has cited farms in this area numerous times for manure discharges that passed through tile lines.
Gibbs has studied the issue with regard to burrows created by the common earthworm, but those aren’t the only routes downward. Soil fractures, root channels and glacial fractures all offer a means of taking manure—and its pathogens, hormones and antibiotics—where it doesn’t belong.
That means into drains and streams and into the hydrological system that recharges groundwater.
“We’ve found it to be a pervasive problem and we held a multi-state/multi-country conference here in Columbus last November to discuss the issue,” said Julie Weatherington-Rice, a soil scientist and geologist with a Columbus environmental consulting firm and an adjunct assistant professor at Ohio State University.
In short, she says, liquid manure and tile drainage don’t make a good match, but tiling is prevalent in this area, as is liquid manure through the increasing number of large dairies.
Janet Kauffman of the Environmentally Concerned Citizens of South Central Michigan (ECCSCM) agrees with the word “pervasive.” Of the 125 citations handed out to farmers in this area by the Michigan Department of Environmental Quality since 2000, 115 were directly related to drainage tile, she said. Other situations became tile issues as contaminated water from flooded fields found its way to tile inlets.
Weatherington-Rice and other researchers continue to explore the problem and look for solutions.
“As we continue to learn more about how and why soils fracture, we find the the system failures can be predicted,” she said, “and engineering measurements can be taken to prevent the failure routes.”
The general rule is to avoid applying liquid manure when tile lines are already flowing and when rain is on the way. Neither of those conditions was a factor in June when silage leachate was used in an irrigation system and flowed into an area drain. In fact, not much more than half an inch of rain had fallen in a month.
Add one more component to the general rule: Avoid extra dry ground.
“If it’s extremely dry, the fractures will be at the surface and already opened,” Weatherington-Rice said. “Ideally, applications should take place when soils are moist enough to have not fractured at the surface, but dry enough to have stopped draining.”
In her area near Columbus, three weeks of hot weather without rain produced surface fractures typical of late summer. When rain finally arrived, the fractures started to swell shut again—at least the ones near the surface.
“Somewhere between three feet and eight feet down, the fractures should stay open year around,” she said, “depending on the specific soil.”
Raising the bar
The silage leachate spill could have been worse, but the flow was halted by farm owners once the problem was discovered.
“In this particular field, there was a gate valve that controlled most of it,” said Jon Russell of the Michigan DEQ.
But tiling is prevalent and similar situations are going to arise.
“It’s a big problem in this part of the state,” he said. “Obviously you’re going to have issues.”
Gate valves are a good second defense, says Tim Harrigan of Michigan State University’s Biosystems and Agricultural Engineering Department. Sometimes soil will absorb the slurry in a plugged tile line, sometimes it won’t, and eventually the line has to be reopened. Because of this, he doesn’t believe valves and plugs should be considered a primary means of control.
“The primary effort should be to prevent manure from reaching tile lines in the first place,” he said.
Close attention must be paid to the rate of application and tillage.
To be fair to farmers, Harrigan said, this is a relatively new problem and one without a simple solution.
Weatherington-Rice agrees about the complexity.
“Our knowledge of how this all works is growing daily,” she said. “Recommendations that we were certain were safe, even five or 10 years ago, appear to be not sufficient in today’s level of knowledge. Our research is growing as fast as it can, but it’s learning from system failures.”
As the number of facilities applying liquid manure increases, the failures will continue a step ahead, she says.
Solutions to the problem are out there, Harrigan says, but it takes some work.
“We acknowledge that causes of the problem are complicated, interrelated and ever-changing based on soil type, cropping patterns, tillage practices, soil moisture, weather, etc.
“Farmers would like to have a clear-cut solution—‘Tell us what to do’—but we can’t do that. It’s far too complicated. We’re not saying that it’s going to be easy or convenient, either. But if they want land application as an option, they’re going to have to get involved. We have to really raise the bar if we want to keep it as an option.”
Janet Kauffman, a volunteer water monitor with the Environmentally Concerned Citizens of South Central Michigan, questions whether the bar will be raised.
The Michigan Department of Agriculture has guidelines in place for manure application through its Generally Accepted Agricultural Management Practices (GAAMPs), but compliance is voluntary.
Don’t apply liquified manure before a rain. She and other volunteers have seen it done time and time again. Don’t apply on frozen ground. It’s done every winter. It’s applied when tile lines are running. It’s allowed to pool on the surface. It’s sprayed and injected on no-till fields and on bare ground. It’s sprayed on growing crops where tillage isn’t possible.
“They haven’t raised the bar, not a notch,” Kauffman said. “They would have to change their whole system of using liquified manure.”- Aug. 24, 2005
Manure management needs to become a priority
The bottom line in contemporary manure management, says Tim Harrigan of Michigan State University’s Biosystems and Agricultural Engineering Department, it that farmers have to make it a priority and they have to want to do it. They need to manage manure land application just as intensively as they manage their feeding program, he said.
“This is a new concept in the sense that we have not historically managed land application of manure with this intensity, but it is really no different from the way they manage their feeding and breeding programs—general guidelines customized and fine-tuned for their farming system.”
The most important factors in keeping manure out of tile lines, Harrigan said, are application rates, application intensity, timing of application, application uniformity and disruption of worm holes and flow channels through tillage.
When using liquified manure as irrigation on a growing crop, tillage isn’t an option. That means it isn’t a good choice for soils that tend to crack.
“This is why manure management with tiled land must become a process—apply, observe, evaluate and monitor,” Harrigan said, “rather than a simple activity that disposes of manure in the field.”
Dilute manure slurries are bacteria laden, highly flowable and likely to pose problems, Harrigan said, and he challenges farmers to find ways to reduce the amount of water entering storage lagoons.
Producers know their fields better than anyone else, he said, and they need to learn how each will process and retain manure. It’s a biological system, just like cattle.
Julie Weatherington-Rice of Ohio State University sees application by spray as a very poor choice due to the lack of control. She refers to research by Dr. Larry Brown, an associate professor at Ohio State University, that points to shallow injection of liquid nutrient as the best method.
“But that requires the limitation of application to between harvest and planting,” she pointed out. “If done in an ideal rotational system a farmer will have a window before spring planting—but that's usually a time of tile flow—in mid-summer after winter wheat is taken off and the fields planted to short beans or pasture, or in the fall before a field is sown to winter wheat or rye cover.”
Weatherington-Rice says that on a smaller farm where the volume of manure is not so great, application becomes integrated as part of the harvest cycle. When farms expand, the rhythm of the land is broken.
“It’s when manure becomes a waste that has to be gotten rid of regardless of the cropping cycle pattern that seems to cause the misfit which perpetuates the manure spills,” she said.
Weatherington-Rice believes farmers are able to prevent accidents.
“Accidents happen when good science is missing or ignored,” she said. “We know better and we know how to keep it from happening. These spills are not accidents, they are predictable and we know how to predict them.”
Janet Kauffman has spent a lot of time monitoring the health of area streams with the Environmentally Concerned Citizens of South Central Michigan and she isn’t convinced that farmers are willing to wait for the few windows of opportunity that offer the best application times.
“It's almost impossible to hit only that narrow window when all the conditions are right—moist but not wet and not dry ground; no rainfall on the horizon; immediate tillage,” she said. “The only way to stop pollution through tiles is to stop the application of contaminated liquids to tiled fields. That means changing the liquid waste system. Plenty of proven technologies are out there—full wastewater treatment, dry waste like composting, intensive rotational grazing.”
Harrigan knows it won’t be easy, but he’s not giving up on land application.
“Is this a challenge?” Harrigan asks. “You bet it is, but there are folks managing manure on tile-drained land successfully. Is it convenient? Probably not, but if producers value land application as an important manure management option, they better get on board.”
Farmers are very resourceful people, Harrigan says, and if they make manure management a priority, it’s surprising how effective it can be.
Guidelines reviewed at a regional workshop in Columbus, Ohio, in November 2004:
• Any field where subsurface drains discharge into ditches that flow to surface water should be considered a high-risk field that is monitored carefully before, during and after application.
• Do not apply manure to tile drained fields when the lines are flowing.
• The available water-holding capacity of the upper eight inches of soil provides the approximate volume of liquid that can be applied before it begins to move through the soil profile.
• Prior to manure application, use surface tillage to reduce the risk of manure reaching tile lines.
• If injection is used, inject only deep enough to cover the manure with soil. Till the soil at least three inches below the depth of injection prior to application.
• Avoid applying before or after a rain. Keep a log of weather forecasts and actual weather conditions 24 hours before and after application with manure application records.
Extension service needs:
• Keep information simple; some producers are not utilizing comprehensive nutrient management plans because they are too difficult to understand.
• Help producers integrate simple manure application rules into the whole farm plan.
• Livestock producers tend to apply manure at high rates and have little incentive to apply manure correctly; education is needed to explain why liquid manure is a problem and to explain risk factors.
• Continued education of personnel from extension service and other agencies (EPA, NRCS, SWCD) about preferential flow issues (worm holes, root channels, soil fractures).
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