Agriculture’s Effect on Environmental Quality: Key Management Issues
Purdue Extension publication WQ-17-W
Sarah L. Brichford and Brad C. Joern, Department of Agronomy; Fred Whitford, Purdue Pesticide Programs
American agriculture enjoys an international reputation for efficient, high quality food production. Hoosier farmers play an important role in that success. Indiana ranks among the top five states in the country in the production of corn, soybeans, tomatoes for processing, peppermint and spearmint. The state is also one of the top five producers of swine, ducks and chickens.
A little over half of Indiana’s 23 million acres is dedicated to row crop agriculture. Including pasture and forest lands, almost 80 percent of the state is in agricultural use. In addition to assuring an abundant and affordable food supply, Hoosier farmers must also strive to protect the environment. The same technology that helps to feed the world has brought increasing pressures on our natural resources. Advanced equipment, improved plant genetics, commercial fertilizers and pesticides are the tools of modern agriculture that have dramatically improved the amount and quality of our food supply. While these tools are a tremendous help when used properly, if mismanaged, the potential for damaging the environment does exist. Good management is the key to protecting environmental quality. This publication describes some important environmental concerns and offers management alternatives.
Exposed soil is susceptible to erosion by wind and rain. Activities such as tillage, crop harvest, construction or any other earth-moving activity, can leave soil exposed. In flat open fields, wind erosion can be a major problem affecting the quality of both air and water. Rainfall causes soil water erosion and, unlike wind erosion, soil water erosion generally occurs on hilly or sloping land.
Sediment is the number one water pollutant from nonpoint sources in Indiana. Sediment causes water to become cloudy, creating an unsuitable environment for many aquatic species, including game fish and even plants. Sediment slowly fills the bottoms of lakes, streams or rivers, reducing their water holding capacity. Sometimes expensive dredging is required to keep boating and shipping channels open and deep enough to hold flood waters. Municipalities that rely on surface water for their drinking water supply must use specialized treatment systems to filter out sediment.
Keeping soil on the field and out of surface waters should be a top priority for Indiana farmers. Several practices will help achieve this result. Conservation tillage leaves crop residue in place to protect the soil surface from both wind and water erosion. Cover crops also hold soil in place. Grass waterways and vegetative filter strips around streams and ponds slow runoff, allowing sediment to settle out before reaching surface waters.
Farmers use many sources of nitrogen for crop production. All of these forms of nitrogen go through transformations in the soil environment. One common form of soil nitrogen is nitrate-nitrogen (NO3-N). Growing crops readily take up nitrate. Nitrate also moves easily with water, and if not taken up by the crop, may leach (or move down through the soil) to ground water. Areas with sandy soils and shallow water tables are particularly vulnerable to ground water contamination by nitrate.
Nitrate contamination of ground water can pose potential health risks, primarily to newborns and infants less than six months old. High levels of nitrogen in surface waters also contribute to excess algae and plant growth, but to a lesser extent than phosphorus.
Since nitrogen is a mobile nutrient, it is extremely important to match fertilizer application rates with the nutrient requirements of the crop. Remember to base nitrogen application rates on a realistic yield goal for each field, or management unit. Give nutrient credits for the previous crop grown and any manure applications made to that field. Proper timing and placement of nitrogen can both improve fertilizer-use efficiency and help minimize the potential for water quality problems. Cover crops, or “trap crops,” can help tie up nitrogen and reduce leaching losses over winter. Also, many of the erosion control practices that slow runoff, such as filter strips and grass waterways, reduce the potential for nitrogen contamination of surface waters.
Over 30 percent of Indiana’s cropland has sufficient phosphorus reserves to meet nutrient requirements for crop production over the next several years. Many farmers continue to apply more phosphorus fertilizer even when soil tests indicate high or very high levels. Over-applying phosphorus does not efficiently use fertilizer resources. This practice can also lead to serious water quality problems in lakes, reservoirs and slow-moving streams.
Since phosphorus is strongly held by soil, it generally is not considered a ground water concern. Phosphorus is the nutrient that causes most surface water quality problems. Any phosphorus not utilized by a growing crop will remain attached to soil particles. If phosphorus-enriched soil particles enter surface waters, the phosphorus may become available as food for algae and other aquatic plants. With an abundant supply of phosphorus during warm summer months, algae populations rapidly increase. Excessive algae growth reduces water clarity and typically produces a surface scum of algae. High phosphorus levels also result in vigorous plant growth near and along the shoreline. Algal scum and excessive plant growth hinder recreational uses such as swimming and boating. When these plants die, the decay process uses large quantities of dissolved oxygen in the water, reducing the amount available to aquatic organisms. Low levels of dissolved oxygen in the water can kill fish and other aquatic organisms.
Since most of the phosphorus that reaches surface waters is attached to soil particles, controlling soil erosion will help reduce phosphorus contamination. Match phosphorus application rates to crop yield goals and soil test levels to avoid excessively high phosphorus levels in the soil. Use regular soil testing to track phosphorus levels over time. If manure is applied, take appropriate credit for phosphorus in the manure so unnecessary amounts of commercial fertilizer are not added.
Modernization of the livestock industry has given rise to highly efficient production systems under one roof in place of the traditional pastured herd. These operations have also created new management challenges in the collection, storage and handling of large quantities of manure.
Manure contains nitrogen, phosphorus, inorganic salts, organic solids and microorganisms. All of these are potential contaminants of both surface and ground water. The runoff from poorly designed feedlots and manure storage facilities can be a direct source of surface water contaminants. Livestock allowed to stand in streams or ponds deposit manure directly into surface waters. Storage facilities (e.g., earthen or concrete pits, lagoons, etc.) that leak can be direct sources of large quantities of manure contaminants to ground water. Excessive or improperly timed manure applications on permeable soils can result in elevated nitrate levels in shallow ground water. Manure applications are also a source of phosphorus in runoff to surface waters.
A combination of proper facility design and land application practices can reduce the impact of manure on water quality and allow manure to be managed as a crop nutrient resource. Select storage facilities appropriate for specific locations, livestock species and manure management objectives. In addition to proper facility design, limiting livestock access to streams and ponds, maintaining grass waterways and filter strips, and diverting runoff around feedlots and resting areas help minimize the potential for manure to contaminate water resources.
Manure has a nutrient value and can be a valuable part of a crop nutrient management program. Test the nutrient content of the manure and match the application rate and timing to meet the nutrient demands of the crop. Use recent soil test results to determine where to apply manure. Rotate fields receiving manure to avoid a build-up of excessive soil test phosphorus and potassium levels.
Pesticides help to increase agricultural productivity by reducing competition from weed, insect and disease pests. Increased agricultural output enhances farm profits, contributes to a wider selection of foods at the marketplace and lowers consumer retail food prices. Increased productivity per acre allows millions of acres of marginal lands to be converted to wildlife habitat and soil conservation uses.
Pesticides impact the quality of Indiana’s water resources through runoff into streams or by leaching to ground water. Pesticides that drift from the application site may negatively impact nontarget plants, fish, birds and beneficial insects. Mishandling of pesticides in storage areas, mixing and loading facilities, and spills often contribute to environmental degradation by contaminating soil and water resources. Health concerns include applicator exposure to concentrated pesticide products, and the public’s long-term exposure to pesticide residues in food and water.
The challenge to the agricultural community is to maximize benefits from sound pesticide management and at the same time reduce environmental risks. Pesticide applicators who read, understand and follow product labels can minimize risks to human health and the environment. Closed systems, returnable containers and water-soluble bags are exciting new approaches that reduce exposure to concentrates. Integrated Crop Management combines scouting, recordkeeping, crop rotations, selective planting and harvest dates, pest-resistant crop varieties, biological controls and economic thresholds to reduce the impact of pesticides on the environment.
Proper storage, spill prevention and rinsing equipment away from wellheads will protect ground water. Managing crop residues and planting grass waterways and filter strips protect surface waters. Technological advances such as tractor-mounted computers and new products that require lower application rates reduce the quantity of pesticides entering the environment. Finally, keeping current on the latest pesticide information will provide the tools necessary for maximizing the benefits and reducing the risks of pesticide use.
Other Farm and Home Chemicals
Farmers rely on many chemicals to keep equipment and buildings in good condition. These include motor oil, fuels, antifreeze, paints and wood preservatives. Improper disposal of these chemicals can lead to serious environmental contamination problems. Unfortunately, disposal options for unused chemicals are limited. Recycle whenever possible. Take advantage of local chemical collection days. Improper disposal of unwanted chemicals is against the law, and you, the property owner, may be liable for all clean-up costs.
Leaking underground fuel storage tanks are the number one identified source of ground water contamination according to the Indiana Department of Environmental Management’s Ground Water Contamination Site Registry. Underground storage tanks that do not have proper anti-corrosion protection are susceptible to leaks. Inspect tanks regularly for leaks and fix suspected leaks immediately.
Protecting Indiana’s Environment
As direct users of Indiana’s natural resources, farmers play a key role in environmental protection. Examine your management strategies and evaluate steps to take that protect the air, water and soil. The quality of Indiana’s environment depends on each of us.
Several resources are available to help plan for environmental protection on your farm. Sources of information and assistance are listed below. Contact any of these offices, as well as your local Soil and Water Conservation District and county Purdue Cooperative Extension office for advice.
Indiana Department of Environmental Management
5500 W. Bradbury Avenue
Indianapolis, IN 46241
Indiana Department of Natural Resources
6013 Lakeside Boulevard
Indianapolis, IN 46278
Office of the State Chemist
West Lafayette, IN 47907
Purdue Cooperative Extension Service
West Lafayette, IN 47907
Purdue Pesticide Programs
Department of Botany and Plant Pathology
West Lafayette, IN 47907
T by 2000 Representative
Department of Agronomy
West Lafayette, IN 47907
U.S. Department of Agriculture Soil Conservation Service
6013 Lakeside Boulevard
Indianapolis, IN 46278-2933
In addition, the following bulletins in the Water Quality series may be of interest:
- WQ-1-W Water Testing Laboratories
- WQ-2-W What Is Ground Water?
- WQ-3-W How to Take a Water Sample
- WQ-4-W Why and How to Test Home Water Supplies
- WQ-7-W Animal Agriculture’s Effect on Water Quality Pastures and Feedlots
- WQ-8-W Animal Agriculture’s Effect on Water Quality Waste Storage
- WQ-10-W Wetlands and Water Quality
- WQ-11-W Sulphur Water Control
- WQ-12-W Distillation For Home Water Treatment
- WQ-15-W Bacterial Contamination of Household Water
- WQ-16-W Land Application of Manure
It is the policy of the Purdue University Cooperative Extension service that all persons have equal opportunity and access to its educational programs, services, activities, and facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran.
Purdue University is an Affirmative Action institution. This material may be available in alternative formats.
Published: July 1993