Contour Buffer Strips (NRCS #332)

Applicable Systems

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About

Contour buffer strips¹ are a conservation buffer primarily planted to reduce sheet and rill erosion, improve water quality, and enhance soil moisture. Prairie grasses or other perennial, herbaceous vegetation are planted in narrow strips around the hill slope between regularly spaced, wider cropped strips that are farmed on the contour.

Key aspects and considerations:

When designing contour buffer strips, consider species selection, climate, topography, soil type, and erosion potential¹.
Contour buffers are most effective on slopes between 2-10%.
Plant strips in rows at least 15 feet wide, in parallel strips for easier access.
Use deep-rooted grasses to maximize nutrient interception.
Avoid using strips as travel lanes for equipment or livestock.
Contour buffer strips require establishment and maintenance of dense and continuous vegetation², with ground cover above 65% on headlands and end row areas.
Less effective when slopes exceed 10% and on topography with rolling hills and irregular slopes.

Benefits and Limitations

ACRE Category	Benefits	Limitations
Soil Health	Improve soil structure, moisture retention, and microbial activity by interrupting water flow, reducing runoff, trapping sediments, and decreasing soil erosion. Increase soil organic matter due to contribution of permanent vegetation to continuous surface litter and root biomass.	N/A
Water Management	Preserve water quality by reducing runoff and sediment transport. By increasing infiltration, contour buffer strips hold more water in the root zone and reduce the potential for ponding or flooding.	High evapotranspiration associated with perennial vegetative cover can reduce soil moisture content.
Nutrient Management	Trap nutrients in runoff water and sediments. Preserve topsoil fertility.	In some cases, buffer strips reduce plant-available nutrients, which may impact crop health. Low effectiveness at reducing the transport of dissolved nutrients.
Agricultural Production	Suppress pests through increased vegetation diversity and natural enemy populations³.	Reduce crop production due to conversion of cropland into buffer strips. Usually, minimal impact on remaining crop yield. Can reduce corn yield in cropland near contour grass buffers.
Biodiversity and Wildlife	Provide food and improve wildlife habitat, thus increasing diversity of pollinators, aquatic species, and other beneficial organisms. Increase plant diversity and natural enemy populations³.	May host pests and pathogens that negatively affect main crops.
GHG Emission	Permanent vegetation enhances soil carbon sequestration and reduces net CO₂ emissions. Continuous surface litter and root biomass increase soil organic carbon. Reduced tillage preserves organic matter and reduces CO₂ emissions. Buffers often require less fertilizer than annual crops, reducing the amount of nitrogen available for denitrification and reducing N₂O emissions.	Buffer strips can emit N₂O if overly saturated or in poorly drained soils.
Economics	Buffers used for forage can provide supplemental income for haying or grazing. Reduce fertilizer and insecticide inputs. Local, state, or national programs offer cost-share programs.	Opportunity costs due to land taken out of production. Implementation costs include tillage, seeds, seeding, or drilling. Maintenance costs include labor and supplies needed for weed control, mowing, and/or burning.

Impact on Agricultural Resilience

By reducing sheet and rill erosion, contour buffer strip systems are more resilient to extreme rainfall events.
Contour buffer strips reduce runoff and increase infiltration, which can enhance soil moisture availability during drought.

Regional Applicability

Prairie strips established in the form of in-field contour buffer strips have demonstrated how this conservation practice works on different landscapes and soils across the states of Iowa, Minnesota, Missouri, Michigan, Nebraska, South Dakota, Wisconsin, Indiana, Ohio, and Illinois.

Case Studies

In Rowley, Iowa, Dick Sloan farms 520 acres where he implements a range of conservation practices, including planting contour buffers with prairie strips. "Highly productive farms now, and in the future, are built around systems which protect native species... Farming is so much more than maximizing today's production of corn and soybeans," states Sloan.
Eric Lee, who farms in the Driftless region of Wisconsin, partnered with NRCS and the Land and Water Conservation Department (LWCD) to implement conservation practices, including contour buffer strips. Describing his decision, Eric states, "This land needed to be farmed differently or it wouldn't be farmed much longer."

Resources

Video. North Central Region Water Network: ACPF - Lecture 18: Contour Buffer Strips
Iowa State University: Science-Based Trials of Rowcrops Integrated with Prairie Strips
University of Missouri Center for Regenerative Agriculture: Conservation Buffers
USDA-NRCS: Conservation Planning Tools
University of Northern Iowa: Tallgrass Prairie Center. Prairie on Farms
Jason Johnson, Iowa NRCS: Contour Buffer Strip album

References

USDA-NRCS (2014). Conservation Practice Standard Document, Contour Buffer Strips, Code 332. https://www.nrcs.usda.gov/sites/default/files/2022-09/Contour_Buffer_Strips_332_CPS_9-14.pdf
Helmers, M. J., Isenhart, T. M., Dosskey, M. G., Dabney, S. M., & Strock, J. S. (2008). Buffers and Vegetative Filter Strips (Chapter 4). In Final Report: Gulf Hypoxia and Local Water Quality Concerns Workshop. American Society of Agricultural and Biological Engineers (ASABE), pp. 43-58. https://www.epa.gov/sites/default/files/2015-07/documents/2006_8_24_msbasin_symposia_ia_session4-2.pdf
Tyndall, J. C., Schulte, L. A., Liebman, M., & Helmers, M. (2013). Field-level financial assessment of contour prairie strips for enhancement of environmental quality. Environmental Management, 52, 736--747. https://doi.org/10.1007/s00267-013-0106-9
Arora, K., Mickelson, S. K., Baker, J. L., Tierney, D. P., & Peters, C. J. (1996). Herbicide retention by vegetative buffer strips from runoff under natural rainfall. Transactions of the American Society of Agricultural Engineers, 39(6), 2155-2162. https://doi.org/10.13031/2013.27719
Bailey, N. J., Motavalli, P. P., Udawatta, R. P. & Nelson, K. A. (2009). Soil CO₂ emissions in agricultural watersheds with agroforestry and grass contour buffer strips. Agroforestry Systems, 77, 143--158. https://doi.org/10.1007/s10457-009-9218-x
Dutter, C., Damiano, L. A., Niemi, J., Miller, B. A., Schulte, L. A., Liebman, M., Helmers, M. J., Cruse, R. M., & McDaniel, M. D. (2023). Contour prairie strips affect adjacent soil but have only slight effects on crops. Field Crops Research, 296, 108905. https://doi.org/10.1016/j.fcr.2023.108905
Miller, T. P., Peterson, J. R., Lenhart, C. F., & Nomura, Y. (2012). The Agricultural BMP Handbook for Minnesota. Minnesota Department of Agriculture. https://www.house.mn.gov/comm/docs/AG-BMPHandbookforMN_09_2012.pdf
Moorhouse, A. L. (2016). Evaluation of CRP contour buffer and filter strips as habitat for native bees and predatory ground beetles. Thesis, Iowa State University, Ames, IA. https://www.proquest.com/docview/1831376284?pq-origsite=gscholar&fromopenview=true&sourcetype=Dissertations%20&%20Theses
Qiu, Z. (2003). A VSA-Based Strategy for Placing Conservation Buffers in Agricultural Watersheds. Environmental Management, 32, 299--311. https://doi.org/10.1007/s00267-003-2910-0
Sahu, M., & Gu, R. R. (2009). Modeling the effects of riparian buffer zone and contour strips on stream water quality. Ecological Engineering, 35(8), 1167-1177. https://doi.org/10.1016/j.ecoleng.2009.03.015
Schulte, L. A., Niemi, J., Helmers, M. J., Liebman, M., Arbuckle, J. G., James, D. E., Kolka, R. K., O'Neal, M. E., Tomer, M. D., Tyndall, J. C., Asbjornsen, H., Drobney, P., Neal, J., Van Ryswyk, G., & Witte, C. (2017). Prairie strips improve biodiversity and the delivery of multiple ecosystem services from corn--soybean croplands. Proc. Natl. Acad. Sci. U.S.A., 114(42), 11247-11252. https://doi.org/10.1073/pnas.1620229114
Stephenson, J. A., Liebman, M., Niemi, J., Cruse, R., Tyndall, J., Witte, C., James, D. & Helmers, M. (2024). The influence of prairie strips sown in midwestern corn and soybean fields on sediment discharge throughout the year. Journal of Soil and Water Conservation, 79(2), 87--98. https://doi.org/10.2489/jswc.2024.00037
USDA-NRCS (2004). Conservation Practice Standard Overview, Contour Buffer Strips (Code 332). https://www.nrcs.usda.gov/sites/default/files/2022-09/Contour_Buffer_Strips_332_Overview.pdf

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Contour Buffer Strips photo 1 — Photo 1: Caption: Contour buffer strips offer a strategy to reduce erosion and retain nutrients on sloped cropland.

Iowa NRCS photo by Jason Johnson.