New tiling technique stores water, nutrients in soil
LUVERNE -- Farmers across the country use nitrogen and phosphorus to build nutrient-rich soil to maximize crop yields, but those same nutrients are being blamed on the growing dead zone around the base of the Mississippi River in the Gulf of Mexico.
Low oxygen levels in the gulf -- referred to as gulf hypoxia -- have grown to such a massive area that the northern Gulf of Mexico is said to be the world's second largest dead zone for marine life. Scientists point to the nutrients washed from farm lands and through the Mississippi River watershed as the cause.
While farmers would prefer to keep the nitrogen on their fields to maximize crop yields, the nutrients often get washed into tiling systems, then carried into waterways, streams and rivers during rain events.
"By adding tile to the fields to increase production, what we've created is a leaky system," explained Doug Bos, assistant director of the Rock County Land Management office in Luverne. "Nitrates are very mobile in the soil, and when you drain the soil, you're pulling any extra nitrogen out and it ends up in the water."
Bos said the demand for tile installation to help drain crop land in southwest Minnesota "has been exponential" in recent years.
"It's just unbelievable as far as tiling requests," he said. "If we don't find ways to (reduce nutrient loss through tile lines) on our own, it is possible we could see new rules or regulations on it. Every drainage meeting I've been to, the speakers talk about the issues at hand."
Just as it took years for gulf hypoxia to reach the level it's at today, it may also take years to reduce the amount of nutrients getting into the river system and being carried downstream. Relatively new technology in Minnesota is hoped to help farmers capture those nutrients before they have a chance to escape.
The Rock River Watershed was recently awarded a grant from the Clean Water Fund, offered through the Board of Soil and Water, to establish a controlled drainage demonstration site along the Rock River, near Luverne. The project is a four-county effort, including Rock, Nobles, Pipestone and Murray.
Bos requested the watershed host a demonstration site to introduce the technology "to our corner" so farmers here could see the benefits of controlled drainage. His goal is that area tiling companies, farmers and agronomists will be able to see first-hand the benefits of holding water on the land.
"It's a win-win situation where we can help protect our water and also improve production," he said. "There has been some yield increase by holding water back during dry times -- like this summer and last summer.
"They won't work in all situations, but they are one tool to use on some of our flatter soils, especially in Nobles County," he added.
Installation of the controlled drainage structure will begin Sept. 3, with an Ag Drainage Field Day slated for Sept. 5. The field day will begin at 10 a.m. at the Blue Mound Banquet Center in Luverne.
Two producers who have controlled drainage structures installed on their farm will share their experience with using the systems during the field day. An expert will also talk about system design, and representatives from the University of Minnesota, South Dakota State University and the Iowa Soybean Association will give presentations. The afternoon will include a field trip to the site of the demonstration project. Lunch, as well as transportation to the demonstration site, will be provided.
"We will have the system installed, but all of the trenches and diggings will be open so farmers can see how these structures and how these biofilters work.
Advanced registration for the field day is requested by calling Bos at (507) 283-8862, ext. 3.
Controlled drainage structures have been used in field tile systems across Iowa for at least 15 years, but the concept is just starting to spread through Minnesota. In fact, Bos said there are fewer than a dozen controlled drainage structures in place in farm fields across the state.
"Iowa's really caught on by putting these in," he said. "Minnesota and South Dakota are still in the demonstration and learning phase."
Controlled drainage structures have the ability to hold water back in the field when production is unaffected, such as during planting and harvest. At the same time, they help during periods of drought by maintaining the water table and providing moisture and nutrients to growing crops.
"By holding water back, we also hold the nitrates in the soil," Bos explained. "It's a multiple-benefit practice -- we prevent nitrates from ending up in the water, and we hold them in the field for the crops to utilize them."
While controlled drainage structures may look different in each field based on the number of acres served, Bos said the structure at the demonstration site is about 5 to 6 feet deep.
"It's like having four file cabinets together," he said. "Given the size of the tile, there's going to be four of these chambers connected in one box."
The chambers hold water back until the farmer chooses to remove boards from the structure, thereby allowing water to be drained from the land.
Bos said the structures can be added to a field at any time by retrofitting the system, although they work best if they can be a part of a farmer's tiling plans.
The Environmental Quality Incentive Program (EQIP) offers cost-share incentives for farmers to install controlled drainage structures, and Bos said the systems can vary depending on the size and scope of the project. Farmers can inquire about cost-share opportunities at their local SWCD or NRCS office.
Bioreactor to be demonstrated
In addition to showcasing the controlled drainage structure during the Sept. 5 field day, participants will get to view a woodchip bioreactor -- an in-ground filter that also removes nitrates during periods when the farmer must lower the water table in his field, such as during planting and harvest.
Bos said the filters can be established in areas that aren't being farmed, such as in grassed buffer strips or along a field edge. As water from the tile flows over the woodchips, the nutrients settle out and reduce the potential for them to end up in streams.
Bos said ongoing studies show a 60 to 70 percent reduction in nutrients reaching public waters through the use of controlled drainage structures and bioreactors.
"It depends on how much runs through the system," Bos said. "In high-water situations, you wouldn't reduce as high a percentage."
Bos said the demonstration site will be monitored in the coming years, and there is potential to do some joint research with the University of South Dakota.
The Minnesota Pollution Control Agency is working on a 10-year plan to reduce nitrogen coming off Minnesota's landscape and being carried down the Mississippi River into the Gulf of Mexico, said Bos.
"Practices like this are at the forefront of their proposed plan to reduce nitrates in water," he added. "We need production agriculture, we need increased crop yields, but we also have to find a way to protect our waters."
It isn't just the waters of the Gulf of Mexico that need protecting -- it's the waters right here at home. Bos said the Rock River Watershed is a shallow aquifer, with a more than 40 percent exchange between surface water and the aquifers.
"Three-fourths of our residents are drawing from that water," Bos said. "If we have high nitrates, it has an effect on our wellfields."