On-Farm Research Expands Farmer Options in Reducing Nitrates

SIOUX CENTER, Iowa – Results from a five-year on-farm research project are helping  a northwest Iowa farmer keep valuable land in production as well as reduce nitrogen runoff into shallow wells that supply water for a nearby community of 7,000 people. The project also shows how research can be used to expand farmer options outlined in the Iowa Nutrient Reduction Strategy.
The project brought together local landowners, officials from the city of Sioux Center, the Sioux County Soil and Water Conservation District, state and federal service providers and professors from nearby Dordt College. This unique partnership looked at five alternative cropping systems and how nitrogen moves through the soil over time. It was funded by the Leopold Center for Sustainable Agriculture and the Iowa Department of Natural Resources’ Source Water Protection Program for Targeted Community Water Supplies. Findings were presented at a March 20 public meeting attended by more than 50 people.
At the forefront, offering land and labor, was Matt Schuiteman of AJS Farms, whose family has been farming the land used in this study for more than 30 years. Beginning with the Leopold Center research grant in 2009, Schuiteman worked with Dordt College environmental studies professor Robb De Haan. They designed and implemented five experimental cropping systems on roughly 40 acres of land adjacent to and above a bank of shallow wells that provide more than 50 percent of the drinking water for Sioux Center.
“The idea was to use perennial crops and cover crops to keep the nitrogen in the upper layers of the soil and available for the next season, and apply just what the crops need when they need it,” De Haan said.   
The systems were designed for standard farm equipment ranged from continuous corn with a winter rye cover crop to perennial grass for hay (common for wellheads but generally a low-income choice for the landowner). Three other systems used rotations of oat-alfalfa-corn; oat/red clover-corn; and soybean-winter wheat-corn. The perennial grass and alfalfa systems receive no commercial nitrogen applications; other systems received nitrogen fertilizer as needed.
Researchers collected 6-foot-deep soil samples from each plot every fall, and divided these into 1-foot segments for analysis of nitrate N concentration. The information was used to construct nitrate N profiles for each plot, and to track nitrate N movement over time. Results illustrate opportunities for farming the land as well as managing water quality.
As expected, the continuous corn with rye left high levels of residual nitrate N in the top 2 ft. of soil. The grass hay averaged five-fold fewer residuals for every year and at every depth, proving to be the most effective system for reducing nitrate N escape into local drinking water.  However, wheat with soybean and corn performed better than continuous corn with rye. Adding a tap-rooted legume, such as red clover or alfalfa, to corn dramatically dropped residual nitrate N levels throughout the profile.
Schuiteman said he was surprised at the effectiveness of alfalfa in managing both the amount and distribution of nitrates in the soil profile. But he was disappointed that wheat and oats were less effective in cleaning up nitrate at the lowest depth.  Based on the findings, he is planning to implement a four-year rotation of two years of alfalfa followed by two years of corn. Oats may be included for weed and erosion management during alfalfa establishment.
Dordt College agriculture professor Ron Vos will analyze profitability of the systems using ISU annual custom rates and prices. Preliminary analysis comparing two of the systems, oat-alfalfa-corn and continuous corn with a winter rye cover crop, showed the continuous corn-rye with the highest average profit per acre but also the most variable for 2009 through 2012. Full results from the project are expected later this year.
For more information and links to a video about the project, go to the Leopold Center website, http://www.leopold.iastate.edu/grants/e2009-22   

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