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Providing Clean Air and Water

Environmental Health and Community Vitality in Agricultural Landscapes

[photo:]Prairie strip embedded in an agricultural (corn) watershed.  The prairie strips increase nutrient and sediment retention, reduce runoff, and increase biodiversity.  Photo Credit: Iowa State University..Research Issue

Reducing sediment and nutrient export from agricultural landscapes is critical to decreasing nonpoint-source pollution in water systems in the Cornbelt region of the United States, where intensively managed rowcrop systems dominate the landscape. 

There is a growing recognition that intensive row crop agriculture as currently practiced in the Upper Midwest lacks both ecological resilience and socioeconomic sustainability.

Our Research

Research by Forest Service scientists with Iowa State University and other partners is demonstrating how integrating perennial plant communities into row crops can enhance both environmental quality and socioeconomic vitality. The Leopold Center for Sustainable Agriculture, USDA Agriculture and Food Research Initiative, and the Iowa Department of Agriculture and Land Stewardship are among the  funding partners for this study, called STRIPS (Science-based Trials of Rowcrops Integrated with Prairie Strips).

  • The experiment began in 2006 with 14 small watersheds at the Neal Smith National Wildlife Refuge and is designed for demonstration on private farmland.
  • Researchers planted a variety of treatments, ranging from conventional agriculture, to mixed systems with prairie conservation strips that cover 10 or 20 percent of the watershed, to reconstructed prairies. Members of the research team study how prairie strips reduce soil erosion, decrease nitrate and phosphorus movement and provide other vital ecosystem services.
  • Recent study results demonstrated benefits for grassland bird and insect populations, water quality and erosion reduction.

Research Results

Our study at the Neal Smith National Wildlife Refuge in Central Iowa is evaluating the amount and placement of native prairie strips (NPS) and their capacity to reduce sediment and nutrient losses from rolling cropland.

The experiment consists of 14 watersheds and four watershed-scale treatments having different proportions and topographic positions of NPS planted in native prairie grasses: 100% rowcrop, 10% NPS of total watershed area at footslope, 10% NPS at footslope and in contour strips, and 20% NPS at footslope and in contour strips. Two other watersheds are 100% restored prairie. A corn–soybean rotation was grown on the cropped land, using no-tillage management.

All treatments were established in fall 2006 on watersheds that were in bromegrass for at least 10 years before treatment establishment.

Results indicated significant increases in NO3–N concentration in soil and groundwater following the placement of the NPS in the row crop watersheds. Nitrate-nitrogen levels in the soil water zone and groundwater under NPS were lower compared with 100% cropland, with the most significant differences occurring at the footslope position.

During four years (2007-2010) following treatment, results showed runoff generation and sediment loss were dominated by a few extreme rainfall runoff events, and the NPS effectively decreased those losses by reducing runoff volume by 37% and sediment loss by 96%.

Similarly, during five years (2007-2011), NPS also effectively decreased nutrient losses with load reductions of 67% for nitrate-nitrogen, 84% for total nitrogen and 90% for total phosphorus.

Greater environmental benefits from NPS were observed in spring and fall likely because perennial prairie plants were active and crops were absent or not fully established. Among watersheds where the NPS were present, the proportion of the watershed in NPS and distribution of filter strips did not significantly influence runoff and sediment/nutrient loss.

The findings from this study suggest that small amounts of NPS strategically incorporated into annual rowcrop systems provides an effective approach to reducing water and contaminant loss from agricultural landscapes under a no-till system.


Smith, T.E.; Kolka, R.K.; Zhou, X.; Helmers, M.J.; Cruse, R.M.; Tomer, M.D. 2014. Effects of native perennial vegetation buffer strips on dissolved organic carbon in surface runoff from an agricultural landscape. Biogeochemistry, 120: 121-132.

Zhou, X.; Helmers, M.J.; Asbjornsen, H.; Kolka, R.K.; Tomer, M.D.; Cruse, R. 2014. Nutrient removal by prairie filter strips in agricultural landscapes. Journal of Soil and Water Conservation, 69(1): 54-64.

Hernandez-Santana, V.; Zhou, X.; Helmers, M.J.; Asbjornsen, H.; Kolka, R.; Tomer, M. 2013. Native prairie filter strips reduce runoff from hillslopes under annual row-crop systems in Iowa, USA. Journal of Hydrology, 447: 94-103.

Helmers, M.J.; Zhou, X.; Asbjornsen, H.; Kolka, R.; Tomer, M.D.; Cruse, R.M. 2012. Sediment removal by perennial filter strips in row-cropped ephemeral watersheds. Journal of Environmental Quality, 41(5): 1531-1539.

Maher, R.M.; Asbjornsen, H.; Kolka, R.K.; Cambardella, C.A.; Raich, J.W. 2010. Changes in soil respiration across a chronosequence of tallgrass prairie reconstructions. Agriculture, Ecosystems and Environment, 139(4): 749-753.

Zhou, X.; Helmers, M.J.; Asbjornsen, H.; Kolka, R.; Tomer, M.D. 2010. Perennial filter strips reduce nitrate levels in soil and shallow groundwater after grassland-to-cropland conversion. Journal of Environmental Quality, 36: 2006-2015.

Schulte, L.A; Asbjornsen, H.; Atwell, R.; Hart, C.; Helmers, M.; Isenhart, T.; Kolka, R.; Liebman, M.; Neal, J.;O’Neal, M.; Secchi, S.; Schultz, R.; Thompson, J.; Tomer, M.; Tyndall, J. 2008. A Targeted Conservation Approach for Improving Environmental Quality: Multiple Benefits and Expanded Opportunities. Iowa State University Extension, PMR 1002. 24 pp.

Research Participants

Last Modified: April 21, 2020