RELATIVE IMPORTANCE  

Summit for Finding Common Ground in Controlling Agricultural Nonpoint Sources of Nutrients

THE SUMMIT

Purpose

Accepted Principles

Central Questions

Participants

Logistics

Reports

EUTROPHICATION

What is it?

U.S. Assessments

International Efforts

Management Programs

AGRICULTURAL SOURCES

Relative Importance

Fertilizers

Animal Wastes

Soil Mineralization

Management Practices

Cover Crops

POLICIES

Economic Analyses

Clean Water Act

State Statutes

Pending Legislation

The relative contribution of  agricultural sources of nutrients into water bodies varies greatly and is a matter of controversy because of the difficulty in directly measuring and estimating nonpoint source loadings.  

The comparison above for coastal waters experiencing eutrophication is from The Pew Ocean Commission Report Marine Pollution in the United States.  

Contributions from agricultural and other sources can be estimated from statistical analyses of water quality monitoring data placed with the context of watershed models, such as the USGS SPAtially Referenced Regressions On Watershed Attributes (SPARROW) Modeling.    

Other approaches used to estimate agricultural contributions are presented in National Soil Tilth Laboratory reports: 

• Geographic Distribution of Excess Agricultural Nitrogen in the Gulf of Mexico

• Agricultural Nitrogen Trends in the Mississippi Basin, 1949-1997

Last updated September 17, 2001