As the weather warms and central Iowa fields begin to dry, farmers Randy and Carol Miller are gearing up for spring planting. At the same time, the Millers are working on their next steps to reduce soil loss and improve water quality.

The Millers, who farm in northern Polk County, are developing plans to install at least one more bioreactor, and maybe two, to remove nitrates from water flowing off their fields. They are also looking into the potential to install a saturated buffer, another technology that has proven to reduce nitrates going into streams, rivers and lakes.

Taking on the challenge of improving water quality and reducing soil erosion is nothing new for the Millers. It’s been their guiding philosophy since they started farming full time in back in the 1970s.

“It’s really a constant process,” Carol said recently. “Like most farmers, we are always looking for ways to improve the way we do things.”

Over the years, the Millers, Polk County Farm Bureau members, have planted buffer strips along creeks and installed additional grass waterways. They have adopted a conservation tillage system to reduce soil erosion and have maintained terraces and riparian buffers. And they have reworked their fertilization program to feed the plants at the right time and reduce nutrient losses.

“I guess our philosophy is that we want to improve the water quality as much as possible and do everything we can to reduce soil erosion,” Randy said. “We want to keep the soil on our farm and improve the water quality. It just makes sense to us.”

Randy, along with their son, Dennis, who farms with them, got the idea for the bioreactor while attending a drainage workshop put on by Iowa State University (ISU). “After a while we just knew it was the right thing to do,” Randy said about the bioreactor. “We wanted to reduce our nutrient loss and help the environment, and this seems like the best way to do it.”

The Millers also met Jacob Handsaker and hired him to tile the field and to build the bioreactor, a 25-foot-wide by 100-foot-long and 4-foot-deep trench at the end of the tile line to create the bioreactor. The trench was lined with plastic then filled with wood chips to create the de-nitrification process.

As water from the tile flows through the bioreactor, the wood chips convert nitrate in drainage water to nitrogen gas that dissipates into the atmosphere. Research by ISU and others has shown that bioreactors are very effective at removing nitrates from drainage water, with removal rates typically more than 40 percent. Initial readings from the Millers’ bioreactor shows they may be removing an even higher percentage.

Planning and installing the bioreactor has not been simple or quick, Carol Miller noted. They have worked closely with the local office of the U.S. Department of Agriculture’s (USDA) Natural Resources Conservation Service (NRCS), Iowa State University and others to design the bioreactors that they installed in 2017 and ones in the planning stages.

As they have added more conservation practices to their own farm, the Millers have seen steady growth in the awareness of water quality and conservation among Iowa farmers.

“There are just a lot more recognition of farmers doing these things now,” Randy said of the conservation and water quality work. “Everyone is doing something a little different, because what works for one farm may not be right at all for another farm.”

To find out more about the Millers’ conservation and water quality efforts, please check out this Iowa Minute at