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Why are Solutions to Agricultural Runoff Needed
Solutions to agricultural runoff are needed because of the effects on receiving streams. Some of the water pollutants found in agricultural runoff from croplands and from livestock operations are nitrogen, phosphorus, pesticides, organic matter (BOD), suspended solids (sediment), pathogens, and perhaps metals and salts. Agricultural runoff is one type of non-point source water pollution, that is, it comes from a diffuse source rather than an easily identifiable effluent pipe from a wastewater treatment plant or an industrial plant. Non-point source pollution is more difficult to bring under control than point source pollution. U.S. EPA recommendations for agricultural runoff mitigation are given in the form of 'management practices' and 'management measures' for various aspects of agricultural operations.
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Water Pollution Effects from Agricultural Runoff
Nitrogen and phosphorus may come from excess fertilizer, rainfall that occurs soon after fertilization, and/or runoff containing livestock wastes. Nitrogen and phosphorus are nutrients that are very useful on cropland, but they can cause overgrowth of plants leading to eutrophication of ponds and lakes. The nitrate form of nitrogen is also a problem if present in drinking water from groundwater sources.
Pesticides in agricultural runoff result from excess pesticide application to crops or pesticide washing off plants shortly after application. Most pesticides should not be consumed by humans or animals. U.S. EPA has set maximum contaminant levels (MCLs) in drinking water for most common pesticides.
Sediment (suspended solids) comes from soil erosion. Sediment in the receiving water causes turbidity, can interfere with aquatic life, and reduces storage capacity of lakes and ponds when it settles out.
Organic matter, typically in runoff from livestock operations, exerts a biochemical oxygen demand (BOD) on water and will cause a decrease in or depletion of the dissolved oxygen in the receiving stream, affecting or killing fish and other aquatic life. Pathogens (disease causing organisms) may also be present in runoff from livestock.
Metals and salts are a diverse group of water pollutants and can end up in agricultural runoff from a variety of sources. Many of them are not a problem if present in small amounts, but may need attention if present at higher levels.
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Management Practices and Management Measures for Solutions to Agricultural Runoff
Several terms like best management practices, management practices, accepted agricultural practices, and management measures, are used in discussion of mechanisms and procedures that help to form solutions to agricultural runoff. The terms management practices and best management practices typically refer to individual practices or groups of practices that are aimed at agricultural runoff mitigation of a particular type, like routing runoff water around eroded areas. The term Management measures usually refers to a group of affordable management practices used together seeking to achieve a more comprehensive goal, like minimizing nutrient losses from agricultural lands occurring by edge-of-field runoff and by leaching from the root zone.
In the first information source given at the end of this article, the U.S. EPA provides extensive information about management measures for agricultural runoff mitigation in six areas of concern:
- Nutrient Management
- Pesticide Management
- Erosion and Sediment Control
- Animal Feeding Operations
- Grazing Management
- Irrigation Water Management
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Management Measures for Cropland Agricultural Runoff Mitigation
Many of the water pollutants of concern in agricultural runoff from cropland are applied to the crops for beneficial use. The phosphorus, nitrogen and pesticides, for example, that end up in agricultural runoff, are not serving their intended function for the crop. This is the principle behind many of the management practices and measures for nutrient management and pesticide management. They are centered on careful control of the amount and the timing of fertilizer and pesticide application, so that they are used by the crop and not flushed away in agricultural runoff.
Erosion and sediment control management measures make use of good agronomic practices for erosion control, thus keeping the sediment in the soil rather than in the agricultural runoff. The irrigation water management measures are aimed at good system maintenance, not over irrigating, and perhaps recovering runoff/tailwater. Much more detail is available in the EPA references below.
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Management Measures for Livestock Agricultural Runoff Mitigation
Management measures for animal feeding operations are primarily concerned with proper management and land application of the manure that is generated. The grazing management measures are aimed at maintaining vegetation on and minimizing erosion from land used for grazing. Much more information about these management measures is available in the EPA references below.
The third reference below can be used to locate a nearby agricultural Cooperative Extension Office in the U.S. They are an excellent source of local advice and assistance in finding solutions to agricultural runoff.
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Sources for More Information About Solutions to Agricultural Runoff
1. http://epa.gov/nps/agmm/: U.S. EPA, National Management Measures to Control Nonpoint Source Pollution from Agriculture, EPA 841-B-03-004, July 2003.
2. http://epa.gov/nps/agriculture.html: U.S. EPA, Agriculture Nonpoint Source Pollution Management Web Site
3. http://www.csrees.usda.gov/Extension/: Location of U.S. Department of Agriculture Cooperative Extension Offices
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Agricultural runoff picture - http://oceanservice.noaa.gov/education/kits/pollution/media/supp_pol06a.html
Cornfield picture - http://awalkabout.wordpress.com/2009/06/09/on-the-road-again-2/