Improving Forage Production and Quality with Native Legumes in Grazed Warm-Season Grass Stands

Improving Forage Production and Quality with Native Legumes in Grazed Warm-Season Grass Stands

Summary

We collaborated with other researchers at UW-Madison to utilize reconstructed native grassland communities that cross a diversity gradient from switchgrass monoculture to high diversity prairie. We installed fencing and watering infrastructure to facilitate rotational grazing with domestic cattle (Holstein heifers). We interseeded native legumes using a no-till drill and implemented disturbance treatments on grazed, mowed, and control plots.

We presented our research objectives in a brownbag lecture for graduate students at UW-Madison, presented a poster examining tradeoffs between ecosystem services and commodity production at the UW-Madison Spring Ecology Symposium, and, in the fall, we led a tour of the site for a grazing group, with participants including farmers and several professional grazing specialists from Wisconsin’s hybrid public/non-profit Resource Conservation and Development (RCD) districts.

Preliminary data suggests that disturbance to the established plant community via mowing or grazing improved native legume germination in the seeding year compared to undisturbed control plots. Native legumes did not accumulate enough biomass in the seeding year to affect forage quality or production. Due to high cattle selectivity, we adapted our forage sampling methods by defining available forage as the subset of aboveground net primary productivity produced by palatable species. Cattle selected primarily warm season and cool season grasses and both native and nonnative legumes. Forage production decreased as plant diversity increased; due to competition from unpalatable forbs, warm season grass cover and thus forage production per acre was lower in prairies than in switchgrass monoculture. Feedback from the herd manager (collaborator Janet Hedckte) indicated that adding warm season grass paddocks to the rotational grazing system at the Arlington Agricultural Research Station alleviated stress on cool season pastures during an exceptionally dry summer, and cattle performance (average daily gain) was average in 2009 despite lower than average precipitation and the introduction of a novel forage production system.

Objectives/Performance Targets

To evaluate native legume establishment and forage production and quality across a diversity gradient, we completed sampling throughout the 2009 growing season to accurately estimate the following parameters: plant community composition (before and after disturbance treatments were applied); aboveground net primary productivity (ANPP); forage availability; forage quality; available soil inorganic nitrogen; and legume germination rates.

We implemented the first controlled experiment using rotational grazing in diverse prairie in Wisconsin, including:
– Plant community composition sampling and inorganic nitrogen sampling furthers scientific understanding of the effects of grazing on tallgrass prairie in the Upper Midwest.
– Documenting cattle forage preferences and sampling forage availability and quality builds a database for analyses that will provide new and fundamental information to livestock producers in Wisconsin who are not familiar with utilizing tallgrass prairie.

Accomplishments/Milestones

• We developed new methods for estimating forage availability that are sensitive to cattle selection preferences in diverse tallgrass prairie.
  We collected data that will be essential for publishing manuscripts in separate peer-reviewed journals relevant to the restoration ecology community and forage production specialists.

• We engaged 4 undergraduate research assistants in rotational grazing research while training and employing them in sampling plant community composition and ANPP.
  We used digital photography to document cattle selection preferences in rotationally-grazed diverse prairie.
  We engaged young professional restoration ecologists when staff and interns from the Aldo Leopold Foundation assisted with plant community composition sampling in August 2009.
  We engaged the prairie restoration community through talks and posters presented in October 2008 and April 2009.
  Approximately 30 graziers and grazing specialists attended a pasture walk in October 2009.

Impacts and Contributions/Outcomes

In southern Wisconsin and adjacent parts of neighboring states, little is known about how rotational grazing affects the tallgrass prairie ecosystem or how utilizing this tool in the ecosystem affects livestock performance. By evaluating this potential management system in a closely-monitored controlled experiment, we are building a data set that will serve as the foundation for analysis and discussion that will be relevant and credible to both the biodiversity conservation and grazing communities. Ecosystem responses and ecological mechanisms illuminated by this research will be relevant to people who manage public and private lands for biodiversity conservation and commodity production, and may suggest new opportunities for blending production and conservation in the Upper Midwest.

Collaborators: