An Integrated Riparian Management System to Control Agricultural Pollution and Enhance Wildlife Habitat

An Integrated Riparian Management System to Control Agricultural Pollution and Enhance Wildlife Habitat

Summary

Rationale:
Intensive agriculture has produced major water quality problems related to non-point source
pollutants produced form row crop and animal production. Natural riparian plant communities
help to control non-point pollution from up-land sources. These communities filter sediments and
associated fertilizers and pesticides, transform the chemicals to environmentally benign products,
and act as modifiers of the aquatic environment of streams. However, when the natural
communities are cleared to for row crop production or are intensively grazed, these functions are
no longer provided. Constructed buffer strips can function as well or better than the native
riparian plant community.

Objectives:
1) Demonstrate and quantify the ability of the multi-species, riparian buffer strip to filter,
transform, and act as a sink for nonpoint source pollutants.
2) Develop a small wetland to intercept and process field tile drainage.
3) Demonstrate the ability of a combination of willow posts, stakes, and cutting to act as a
durable and environmentally acceptable system for long-term stabilization of eroding stream
banks.
4) Evaluate the impact of the multi-species, riparian buffer strip, the field wetland, and the stream
band willow planting for wildlife habitat and use.
5) Evaluate the costs of establishing and maintaining the three riparian management systems
being demonstrated.
6) Develop appropriate technology transfer materials and activities for farmers, policy-makers,
farm groups, and others.

Methods:
An integrated riparian management system was developed along a central Iowa stream and
consisted of three components: a multi-species riparian buffer strip, soil bioengineering
technologies for streambank stabilization, and a constructed wetland to intercept and process
nonpoint source pollutants in agricultural drainage tile water. The general multi-species riparian
buffer strip layout consisted of three zones. Starting at the stream bank edge, the first zone
included a 9 m wide strip of 4-5 rows of trees, the second zone was 4 m wide strip of 1-2 rows of
shrubs, and the third zone was a 7 m wide strip of native warm-season grass. The trees and
shrubs provide perennial root systems and long-term nutrient storage close to the stream, while
the grass provides the high density of stem needed to dissipate the energy of surface runoff from
adjacent cropland.

Results:
After six years, soil water in the unsaturated zone under the buffer strip never exceeded 3 ppm of
NO3N, or 1 ppb of atrazine, even though concentrations as high as 30 ppm and 8 ppb,
respectively, were measured in the crop field. However, nitrate concentrations in the shallow
groundwater were highly variable between adjacent transects, suggesting that nitrate contained
within shallow groundwater may be moving preferentially across the buffer strip. The
installations of bioengineering technologies have been very effective in stabilizing streambanks,
and the establishment of the riparian management system has dramatically improved wildlife
habitat on the farm. Results demonstrate that nearly four times as many bird species are using the
buffer strip than are using an adjacent, non-buffered stream segment.

Potential contributions and Practical Applications:
The components of the buffer strip act as a permanent corridor within the cropping system matrix
of the agricultural landscape. As such, the corridor provides wildlife habitat, improves the
in-stream environment, reduces winds on the downwind landscape, provides habitat for
beneficial insects and birds, sequesters carbon that would otherwise contribute to global
warming, intercepts and immobilizes nonpoint source pollutants, improves soil quality, and traps
surface runoff. Visual estimates suggest that at least 90 percent of the sediment leaving the
cropland is being trapped by the buffer strip. Similarly, inputs of nitrate and atrazine form the
vadose zone and shallow groundwater to the creek have been reduced by 80-90 percent each year
by the buffer strip.

Farmer Adoption and Direct Impact:
The adoption of the riparian zone management system has begun to gain momentum. The model
has been subscribed to by the USDA-Forest Service/USDA-NRCS National Agroforestry Center
and the National Arbor Day Foundation. Partnerships have been formed with scientists at the
National Agroforestry Center and the University of Nebraska to adapt riparian management
models to the Midwestern and Great Plains regions. Locally the practice has been adopted by
several neighboring farms and in other areas throughout the state.