Farm Horizons, Feb. 2016
Best practices for agricultural drainage tile placement
By Tara Mathews, Correspondent
Agricultural drainage tile has been used in crop fields for centuries and can benefit to crops in many ways, including faster drying time, higher crop yield, and fewer drown-out spots.
Though the drainage tile is beneficial for many farmers’ crops, it can be detrimental to wetlands and wildlife, just as much.
Although it’s a delicate balance between keeping farmers’ fields dry enough for crops and keeping wetlands safe, it is achievable through careful planning and placement of drainage tiles, which is why there are state and federal regulations regarding the matter.
Steps to tiling
The University of Minnesota Extension Office recommends first contacting the local soil and water conservation district, natural resources conservation services, and watershed administrative unit before making any plans for agricultural drainage tiling.
After contacting those local resources, a farmer should determine what their crop response might be for the area to be tiled, the impact of a system on convenience of field operation, and changes to input and other costs associated with a drainage system.
The Wright Soil and Water Conservation District (WSWCD) recommends also contacting the local United Stated Department of Agriculture (USDA) prior to any agricultural drainage project, to verify the project will meet state and federal regulations.
“The landowner must use a certain amount of judgment to determine if it’s necessary. For example, if the area to be tiled drowns out regularly or has wetland vegetation such as cattail growing in it, the landowner should definitely stop in to discuss their project in more detail,” Andrew Grean, Wetland Specialist at WSWCD explained. “On the other hand, if the area to be tiled is located on top of a hill that is clearly upland with no wetlands nearby, they can most likely proceed with their project without worrying about breaking any wetland laws. The only way a landowner can be 100 percent certain is to stop in and talk with us.”
An excavating contractor who provides agricultural drainage tiling installation has to pay attention to guidelines, as well, according to Ken Mathews of Mathews Digging in Silver Lake.
“We can get in trouble if we are placing tile in a known wetland area without proper permits, and set-backs, too,” he noted.
Mathews begins his projects by doing a survey of the area, which includes the level of moisture, distance from visible wetlands, and slope of the area.
He determines how deep the tile would need to be placed, the size of the tile needed to produce maximum results, and if the farmer needs to file for any kind of special permit or variance.
“Then, I send the farmer to file for permits, and find out if the area is protected at all,” Mathews stated.
He usually begins the surveying process in March, and the tiling projects in April, he said.
Generally, agricultural drainage tile installation costs about $400 per acre, but varies depending on the depth and size of tile.
“Most farmers will decide a price limit, then we tile what we can within that limit,” Mathews noted.
After a price limit is determined, Mathews and the farmer will decide which fields are in the worst drainage area, and start with those.
“Then, there’s what’s called farm-able wetlands,” Mathews said. “There are already tiles there that have been sort-of ‘grand-fathered in,’ that sometimes need work.”
In the case of farm-able wetlands, one is able to replace or fix tiles that have previously been installed, but can’t move them in any direction.
“Any new tiles have to be the same size, placed in the same spot, at the same depth,” Mathews commented.
Often in cases of farm-able wetlands, there will be an inspector that goes to the job site to ensure proper tile replacement.
“That only happens about one out of five times, but it does happen,” he added.
There have been instances at which Mathews has had to dig up recently-installed tile for an inspector, because of complaints of neighbors or people passing by that thought it was not installed properly, or because of issues thought to be caused by the tile.
“Not that we try to make mistakes, but it does happen,” Mathews noted. “Although most of the time, we dig it up, they check, and it’s just fine.”
“Depending on the wetland, there have been times we needed to stay more than 150 feet away from them,” Mathews said.
The distance a tile needs to be kept from a wetland is usually determined by the depth and size of tile a farmer desires to install.
“Usually, around 4 feet deep is ideal,” he commented. “If it’s too shallow or too deep it doesn’t pull the water the way it’s designed to, and doesn’t work at maximum efficiency.”
Sometimes, if a wetland is directly through a field, a farmer can use what is called “non-perf pipe,” which has no holes to allow water in, and therefore will not drain.
The farmer can have his tile go from one side of a wetland to another without draining it using the “non-perf tile,” yet can get the proper drainage in his field.
Mathews completes about 4,000 to 5,000 feet of drainage tiling per day in the spring and fall.
“There’s about three weeks in the spring, and one month in the fall to complete tiling and not affect the farmers’ growing seasons,” Mathews commented.
Agricultural drainage tile does not just affect the area directly around it, according to Grean, it has what is called a “lateral effect” associated with it.
The lateral affect means that the tile doesn’t only drain the area around it, but that it can draw water from many feet away. The size and depth of a tile, soil type, and proximity to a wetland are factors considered when determining the set-back distance of the tile placement.
“It can go from 50 to hundreds of feet away,” Grean noted. “Individuals proposing to tile near wetland areas are highly encouraged to stop in and verify that they meet any applicable set-back requirements.”
Because the drainage tile can degrade the quality of wetlands, drain them down, and potentially destroy them altogether, careful placement is necessary to achieve the delicate balance.
“Draining a wetland is no different than draining a lake or a stream. If the water is removed from a lake, the plants and animals that have evolved to live in those conditions will die. The various plants and animals that live in and rely on the seasonal fluctuation of water levels in wetlands are affected when the hydrology is changed by tiling,” Grean stated.
Increasing the water level in a wetland by draining other areas into it can have the same affect as draining the wetland, he added.
“It was once thought that wetlands acted as the ‘kidneys of the landscape,’ filtering nutrients and other contaminants before they end up in our lakes, rivers, and streams,” Grean commented. “Sampling and research has shown that this is not always the case.”
When a wetland reaches a certain threshold, it begins to lose its ability to act as a filter, leaving all of the contaminants to just sit there, negatively affecting the wildlife therein.
Recent studies have shown the wetlands can export nutrients to nearby lakes and streams, as well.
If it’s not a wetland area, a farmer can place drainage tiling where it is going to be most efficient, and doesn’t have to worry as much about the size of tile, depth, or amount.
“Nowadays, a lot of farmers are pattern tiling, even if it’s good land, because they can plant earlier in the spring,” Mathews noted.
Pattern tiling allows the field to dry and warm faster, he added.
There is no limit to the amount of drainage tiling a farmer can install, as long as they meet all state and federal requirements, according to Grean.
“Although there are undeniable yield benefits that can result from the addition of tile, it does not come without a cost,” he noted. “In most, these are societal costs, such as the exacerbation of flooding, nutrient and sediment transport, and habitat loss, which have all been linked to the increase in drainage.”
All of these factors have contributed to the current state and federal regulations that have been passed on use of agricultural drainage tiling.
“Often times, a resource or production concern raised by an individual cannot be solved by simply adding more tile,” Grean stated. “We encourage landowners to consider other factors, like nutrient management, tillage, soil health, and erosion that cannot be addressed simply by the addition of tile.”