2.2 AGRTCTJLTIJRE.RELATFn SOURCES 



Introduction 



Eutrophication and sedimentation of esmaries and effective nianagement of nutrient and 

 sediment loadings has been a major issue for a number of years. Major efforts to reduce 

 these loadings have foraied the basis of programs in the Chesapeake Bay, and other large 

 estuaries and in smaller systems on the Gulf Coast, Long Island, Cape Cod, and on the 

 south shore of Rhode Island. The EPA Chesapeake Bay program estimated that 

 agricultural lands, which contribute 60 percent of the nitrogen, 27 percent of the 

 phosphorus, and much of the 9 million cubic yard loading of sediment to the system, are 

 by far the greatest source of contaminants entering the Chesapeake estuary. 



A much smaller proportion of the 1,061,000 acre Narragansett Bay basin is devoted to 

 agricultural use, and most farm operations are small and interspersed among non- 

 agricultural land parcels and population centers. For that reason, it is extremely difficult to 

 distinguish agricultural non-point source pollution from other non-agricultural non-point 

 sources in the Bay watershed. Construction activities, use of chemicals in home lawn-care, 

 and stormwater runoff, for example, contribute certain contaminants which are also 

 associated with agriculture-related pollutant loadings. 



Analytical methods developed as part of the Nationwide Urban Runoff Program, and 

 presentiy being researched at U.R.I., promise to increase the accuracy with which problem 

 areas can be identified. Further development of the Rhode Island Geographical 

 Information System will also be of critical importance in targeting control efforts. Until 

 these tools are readily available. Conservation District staff and researchers must rely on 

 limited existing source statistics and knowledge of site characteristics to gauge the 

 magnitude of these problems. Available information indicates that agricultural sources, 

 though of smaller magnitude than some other non-point pollutant sources, still deserve 

 aaention. 



AGRICULTURAL INPUTS AS POLLUTANT SOURCES: ISSUES OF CONCERN 



The nature and extent of agriculture-related non-point source pollution is direcdy related 

 to the manner in which land is used and managed. Land resources used for agricultural 

 purposes are generally managed intensively, and, if proper control measures are not 

 established, may create concentrated sources of pollutants which induce complex 

 cumulative effects. ( Row cropping, for example, involves land disruption as well as 

 application of chemical fertilizers and pesticides.) 



The most visible source of surface water contamination due to agricultvire is sediment 

 erosion. On average, 25 to 40 percent of the soil that runs off a field reaches a waterbody 

 (U.S. EPA, 1984). Although the disparity between gross erosion and sediment delivery 

 precludes direct correlation of calculated erosion rates with water quality problems, several 

 methodologies have been developed to estimate loadings. The potential for sediment 

 delivery depends upon an individual site's soil characteristics, slope, climate, and 

 proximity to surface waters. Resulting pollution levels depend upon crop type, tillage 

 practice, and other management factors. 



The potential water quality impacts of sediment erosion are numerous. Not only does 

 the physical presence of soil particles in water affect physical quality (including light 



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