Improving Outcome Predictability, Multifunctionality and Cost-effectiveness in Nutrient Reducing Prairie Strips

Date: 
Aug 2019

Issue

The contour prairie strip could be a valuable conservation tool to reduce nutrient loss from agricultural fields. Previous research has shown that prairie strips eliminate up to 90 percent of surface runoff of nitrogen and phosphorus and reduce concentrations of shallow groundwater nitrate.  Further, the roots of these prairie strips fuel the denitrification process, suggesting multiple uses in saturated buffers and marginal lands. Prairie strips can also enhance other ecosystem services, including soil quality restoration, wildlife habitat and resilience to flooding. To optimize the potential value of prairie strips for nutrient reduction, we need applied research focused on improving the chances of successful implementation, improving cost-effectiveness and maximizing multiple ecological benefits.

Objective

The objective is to improve the implementation, multifunctionality and cost-effectiveness of prairie contour strips for nutrient reduction by pursuing three lines of research:

  • validating the conclusions of a 2015 Nashua study at a different location to strengthen the scientific basis for practice recommendations;
  • evaluating fall versus spring plantings on stand establishment, cost-effectiveness and functionality; and
  • refining the balanced seed mix strategy in light of the realities of native seed markets, by characterizing the most multifunctional and cost-effective composition of graminoids (grassy herbaceous plants) in a 1:1 grass:forb seed mix designed for prairie strips.

Approach

The general approach will use techniques implemented at the field scale, using appropriate equipment (tractor mounted seed drills, mowers) so that results are directly applicable to farm operators and contractors. Experimental field trials at the Tallgrass Prairie Center, Cedar Falls, Iowa, replicates a previous INRC-supported study at a new site with a different soil type and cropping history. A new factor will examine the impact of seeding time. The study consists of a spatially blocked split plot design with three factors (seed mix, mowing, seeding time) and six replicates. We will collect data at the site in August/September 2019 and 2020 and record plant density, cost per thousand plants, and measures of functional and species diversity.

The study will also evaluate the graminoid (grassy herbaceous plants) composition in the 1:1 grass:forb seed mix design now being specified for prairie strips in Iowa. This study will be conducted at the Roadman Farm.  

In addition, we will conduct two low-replication screening trials for possible inclusion in fully replicated experiments: first, to continue monitoring establishment between a standard seed mix and a tailored “dry site” seed mix on dry soils (Fayette County); second, to examine the impact of seeding depth on small-seeded species.

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