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Evaluating the Effectiveness of Best Management Practices (BMPs): Fate and Transport of Microorganisms in Animal Wastes
Animal manure may contain multiple pathogenic organisms. In the United States, animal manures are often applied to farm fields as a disposal mechanism and as a fertilizer. When animals live in concentrated areas, as in Concentrated Animal Feeding Operations (CAFOs), the amount of manure produced is often too great for reasonable application to fields and the quantity of nutrients may exceed the the crops' intake capacity. Among the human pathogens are Escherichia coli O157:H7, Salmonella spp., Listeria spp., Campylobacter spp., Giardia, Cryptosporidium. When manure is applied to farm fields, runoff may contaminate nearby waters with nutrients, bacteria, and protozoa.
The USDA Natural Resources Conservation Service (NRCS) has produced many manuals for the control of soil erosion and nutrient loss because these factors significantly effect crop production. However, the effects of soil management practices on the movement of microorganisms remains largely unexplained. When farm animal populations are low, the numbers of microorganisms originating from the farm cannot be easily distinguished from the numbers produced by wildlife. Recent research has shown that BMPs used in farm fields do effect the movement of organisms from the fields. The goal of this research is to develop ways to evaluate the effectiveness of different BMPs to control the movement of microorganisms from fields to streams.
Approach: The USDA Agricultural Research Service (ARS) maintains several research watersheds throughout the United States. In those watersheds, the ARS monitors established networks, measuring water quality parameters at field-, small, and large watershed-scales. ARS will collect samples at points in the watershed where animal wastes are applied to fields. Some fields do, do not, and will have BMPs installed. A sample collection program will measure microorganisms in runoff and tile drain water from fields, which will provide an estimate of the ability of BMPs to reduce the movement of microorganisms from the manure application site. A sampling plan was developed to evaluate an innovative waste management system that Iowa State University established on a beef feeding research area. This system consists of a settling basin followed by an infiltration basin whose drains lead to a constructed wetland, and is supposed to reduce the nitrogen and bacterial load of the runoff before it reaches a nearby stream.
The research will also examine several methods for identifying the sources of microorganisms. Proper placement of BMPs in the landscape depends upon identifying the source of pollutants to be controlled. Many techniques have been developed, but are very labor- and cost-intensive. Antibiotic resistance patterns, DNA, RNA, and virulence factors may help identify the source of particular organisms. Some of these techniques will be tested for application as source-tracking methods.
Contact: John Haines (EIMS#131912)