Assessment of pasture management practices on microbial biomass, composition, and functional diversity

2008 Annual Report for GNC07-081

Project Type: Graduate Student
Funds awarded in 2007: $9,924.00
Projected End Date: 12/31/2009
Grant Recipient: University of Wisconsin-Madison
Region: North Central
State: Wisconsin
Graduate Student:
Faculty Advisor:
Randall Jackson
University of Wisconsin-Madison

Assessment of pasture management practices on microbial biomass, composition, and functional diversity


Soil resilience is a concept deemed important in our understanding of soil quality and sustainability and is thought to be facilitated by functional diversity of soil biota. While the diversity of microorganisms in soils is thought to be high, some management practices, such as conventional tillage, can deteriorate soil physical properties, and bring about a decline in total microbial biomass. Our understanding of the impacts of human activities, including grazing, is important to our understanding of the role microorganisms play in soil processes and maintenance of soil quality. To better understand the potential of ecosystems to respond to disturbance, more information on microbial community and functional group composition, abundance, and their distribution within soils is necessary. While the impact of livestock production practices on aboveground biomass is well studied, their impacts on belowground heterotrophic communities are not.

Objectives/Performance Targets

I will assess microbial biomass, composition and diversity under 4 pasture management treatments–management-intensive rotational grazing, continuous grazing, harvesting for hay, and a no disturbance control–on 8 southern Wisconsin farms. I will use a modified Phospholipid Fatty Acid/Fatty Acid Methyl Ester Analysis, which provides accurate estimates of viable microbial biomass as well as distinct fingerprints for microbial diversity. Results will improve our understanding of how pasture management affects soil quality, which is important not only for livestock production, but also to support adoption of more sustainable perennial grassland agroecosystems.

Expected short-term outcomes:
Under 4 pasture management treatments I will:
1) quantify total microbial biomass, fungal:bacterial ratios, microbial community composition and functional diversity, and
2) compare variability of response variables among pasture management treatments within and across 7 grazing farms.


To assess microbial biomass, composition and diversity under different management treatments using a modified Phospholipid Fatty Acid/Fatty Acid Methyl Ester Analysis (PLFA/FAME) we have:
1)collected soil samples from 7 Wisconsin farms,
2)processed soils for analysis and,
3)performed PLFA/FAME.

The next steps will be:
1)to process the data and perform data analysis and,
2) write the final report.

Impacts and Contributions/Outcomes

Information generated from this research will expand the knowledge base about management effects on pasture ecosystems giving farmers, agencies, and policy makers a better understanding of the links between soil, water, air, and biotic resources, which will assist in making management decisions. Furthermore, this research will foster greater understanding between researchers and farmer/producers.

Long-term outcomes:
Improved management of grazed pastures will optimize the tradeoff inherent between livestock production and environmental stewardship. Such an optimization will result in more sustainable farming, which should lead to more vital rural communities.


Teresa Balser

Associate Professor - Soil Science
University of Wisconsin - Madison
Randall Jackson

PI; Assistant Professor - Agronomy
University of Wisconsin - Madison