Pros and cons of tiling
By LARRY KERSHNER
ALTOONA – Updates on drainage law, pattern tiling and planning awaited nearly 100 farmers and landowners Dec. 10 at a drainage school in Altoona.
Hosted by Iowa State University Extension, the day-long workshop covered the essentials in designing and planning a new drainage system or retrofitting an existing system while learning about environmental impacts and new technologies that may be useful in minimizing negative environmental impacts.
Dr. Kapil Arora, an Iowa State University Extension ag engineer, emphasized that any planned drainage project has to start at least a year in advance.
“You have to check all local, state and federal regulations,” Arora said.
Information needed for planning is knowing affected soil types, outlet location and size, the path needed to get tile to the outlet and any downstream limitations.
“If a creek stays too high,” he said. “You won’t get any drainage.”
Outfitting is another issue, Arora said.
“It has to go somewhere. You may have to work with a neighbor.”
He said scheduling a contractor to do the work may also take time.
“If a contractor is good, there’s a reason they are busy,” Arora said.
The size of the project may also determine how soon a contractor will get to the field.
In determining the soil types to be drained, Arora directed the audience to the U.S. Department of Agriculture’s Web Soil Survey, which has all the 1970s Iowa soil surveys online.
This is an interactive website in which a field’s owner or operator can outline the targeted area for tiling and the site will reveal the names and locations of soil types in the pattern.
“Your planning will always start with where will the outlet be,” Arora said after explaining the site.
Its size will be determined with how much water is to be removed from each acre each day – .5 or .75 of an inch is typical.
Since tile water is generally ladened with nitrates, which is a hazard to surface waters, the workshop covered alternatives for filtering N from tile water.
- Reestablishing a natural wetland, where water is slowed, giving plants a chance to use the nitrates and for bacteria to break it down, releasing it as harmless nitrate gas in the air.
- Saturated buffer, where tile water is channeled into a buffer zone adjoining a waterway. That water is released underground, giving plants there a chance to use some of the nitrates before it reaches the stream.
- Establish a bioreactor, in which tile water is directed through an underground pit filled, usually, with wood chips. Bacteria in wood chips break the nitrates down to nitrate gas, which rises through the soil and blows away.
- Controlled drainage where devices at the edge of the field have gates that hold back tile water, backing it up the system to be available for plants during dryer times. In heavy rain events, the gates are opened to release excess water.
Pros and cons
Matt Helmers, an ISU ag and biosystems engineer, outlined the positive benefits of drainage – increased yields and trafficability for field work. He pointed out water quality and loss of wetlands as drawbacks.
He then offered various options for siting subsurface drains, the conditions that require them and factors that will help in designing them, including:
- Spacing: Determined how fast soil will allow water to reach the tile.
- Outlet size: Its capacity will determine how fast water is taken away.
- Drainage coefficient: Determining how much water the design can remove from a field in 24 hours.
Economics of tiling
Kelvin Leibold, an ISU Extension ag business management specialist, noted that not all soils are created equal and therefore the payback in tiling will differ from field to field.
He also told farmers and landowners that there are more ways to measure if tiling will pay for itself besides increased yields.
“Does how soon you can get into the field after a rain make a difference to you?” Leibold asked. “Or are you looking for a tax deduction?”
In addition, there are several factors to calculate including what will change from an income standpoint and what will change in terms of input costs.
Since soils differ in water-holding capacity, the anticipated yield advantage will differ and this difference should be compared to the tiling costs.
Other factors in budgeting for new tiling include:
- Costs of tile determined by the size.
- Costs will change with different installation methods, patter designs and hook-ups.
Leibold said that ISU’s Ag Decision Maker website offers a worksheet for designing a tile project for budgeting and anticipated returns on investment.
He outlined different methods for a renter to convince a landowner to consider tiling improvements with tax and payment options.
“But the bottom line for tiling,” Leibold said, “is, ‘Is it legal?'”
ISU Extension was joined by Iowa Farm Bureau of Polk County, various industry partners and Natural Resources and Conservation Service, plus industry representatives from Prinsco, ADS, Midwest Plastic Products and Agri Drain.
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