Through the past 50 years of farming, Webster City, Iowa, farmer Arlo Van Diest has tried many different pieces of equipment and many different practices. His goal is to leave the land better for future generations.
From moldboard plows to chisel plows and now strip-tilling and bioreactors, he has continually worked for improving conservation on his 2,300-acre farm in north central Iowa.
"Putting in a bioreactor nearly 3 years ago was an easy decision for me because it was supposed to decrease nitrates in the water,” Van Diest says. "I’ve seen the benefits of the first one, with a nearly 70% reduction in nitrates in the water. I wanted to put another in to see if I would have similar success.”
Van Diest lives in the Boone River Watershed, which is one of the watershed areas targeted in the USDA’s Mississippi River Basin Healthy Watersheds Initiative. The goal of the MRBI is to reduce nutrient loading in the Mississippi River Basin, which contributes to both local water-quality problems and the hypoxic zone in the Gulf of Mexico.
The Boone River Watershed, which is divided into eight sub-watersheds, can receive higher than normal payment rates to implement new conservation practices that avoid, control and trap nutrient runoff, as well as improve wildlife habitat and maintain agricultural productivity. Bruce Voigts is the MRBI project coordinator for the Boone River area in north central Iowa.
“Several bioreactors are planned in this area to help improve the watershed, which in turn helps improve the Mississippi River and eventually reduces the hypoxic zone in the Gulf of Mexico,” Voigts says.
Bioreactor specs Keegan Kult is the watershed management specialist for the Iowa Soybean Association. He assists in the research and water monitoring for ISA’s environmental programs and services, which includes the installation and management of bioreactors.
“A bioreactor is essentially a buried trench on the edge of a field filled with a carbon source, through which tile water is allowed to flow,” he says. “We determine the size of bioreactor needed based on the tile size and water flow through the tile, as well as the rate the water flows.”
Those helping with the planning of the bioreactor work with the farmer in order to determine where the tile flows with the most water. This is generally the best place to install the bioreactor.
“The carbon source, which is generally wood chips, provides material upon which microorganisms can colonize. Using wood chips as a food source, the microorganisms begin breaking down nitrate in the water and expelling the nitrate as dinitrogen gas (N2), a primary atmospheric component,” he explains.
The bioreactor has no adverse effects on crop production and is designed in a way that it does not restrict drainage. A control structure determines the amount of tile flow that is diverted into the bioreactor. During periods of high flow, excess water bypasses the bioreactor and continues to flow through the existing field tile.
Van Diest says he has learned how to control the water based on rain incidences.
“If we have a big rain, the bioreactor cannot keep up and has to be bypassed, but generally I know how to control the water in the control structure,” he says.
His current bioreactor is 126-by-31-feet, or 500 cubic yards total. It's intended to treat 45 acres of crop ground.
The hole is dug and then the control boxes are placed where the water can be monitored correctly from the input box and output box. The hole is filled two-thirds full with woodchips, which is then covered with a semi-permeable geofabric to prevent soil particles from entering the wood chips and causing problems with the bioreactor’s filtering process.
A layer of soil is put on top of the geofabric and smoothed out. The farmer then re-establishes grasses on top of the bioreactor.
“In some states, farmers are allowed to plant over the bioreactors, but in Iowa they always put in a buffer or filter strip,” Kult says.
Samples are taken from the inboxes and outboxes on a regular basis, either once per week or biweekly. These samples are tested for nitrates to determine the success of the bioreactor.
Since bioreactors are fairly new, Kult says their longevity is yet to be determined.
“The first one was installed about 14 years ago and still seems to be functioning. We think it is safe to say that a bioreactor will work for 10 to 15 years. After that, it will likely need new wood chips in order to work properly,” he says.
The hope is for the bioreactor to reduce nitrate levels by 35% to 50% or more, as in Van Diest’s case. While the cost of installing a bioreactor is about $8,000, it can be offset with funding from the Iowa Soybean Association and U.S. Department of Agriculture agencies.
“In the targeted watershed areas, there is a lot of funding available for farmers, thus making the bioreactors a very attractive practice to include on farms,” Voigts says.
Other conservation practices Van Diest has continually used include different equipment and practices on his farm to ensure good conservation and prevent any loss of soil off his ground.
“I remember when we used the moldboard plows, and they had a purpose back then. When we switched over to chisel plows, there seemed to be even less dust blowing around,” he says. “After I attended the Commodity Classic about 10 years ago, I heard about a practice that I wanted to try — strip-tilling.”
Van Diest’s strip-till system leaves large amounts of crop residue that help protect against erosion from wind and water. He leaves the soil and crop residue undisturbed from harvest to planting.
During the planting process, he clears a small strip of residue for planting and applying fertilizer. At first, he only strip-tilled soybean ground, but then tried corn ground as well, which was harder to work through because of the corn residue.
“Once I learned how to make it work, I did all my ground in strip-till,” he says. “The soil structure has improved greatly and it's very easy to plant now.”
Van Diest has also encouraged many of his neighbors to convert to strip-tilling and has hosted several meetings on his farm to explain the practice to other farmers.
Because of the economics on his farm, he plants about three-fourths of the farm into continuous corn. The use of strip-till has led a clean seedbed and no compaction in the seedbed, allowing water to drain properly.
“The best improvement I have seen on this ground is that less nitrogen is needed on the continuous corn acres because of the strip-till,” he explains. “For every year of continuous corn I do on the strip-tilled ground, about 10 pounds less of nitrogen is needed.”
Trying new practices is something that Van Diest wants to pass on to future generations who will be farming the land.
“I think the desire to leave the land better than we found it and make the needed changes through the years is how all farmers should manage their ground,” he concludes.
Voigts agrees with Van Diest, saying, “If we don’t voluntarily have good conservation management practices, we might be forced into following regulations on our land that will be even more difficult to manage.”