Fertilizer Runoff: Water Pollution And Its Environmental Impact

Fertilizers are a common agricultural product used to enhance soil fertility and help plants grow. However, they can also have detrimental effects on water sources if not properly managed. When excess fertilizers run off into water bodies, they can cause eutrophication, leading to oxygen depletion and the creation of dead zones where aquatic life cannot survive. Additionally, fertilizers can contaminate drinking water supplies, posing risks to human health, including methemoglobinemia or blue baby syndrome in infants. To prevent these issues, it is crucial to apply fertilizers properly, avoid overuse, and minimize runoff by following recommended practices for lawn and garden care.

Eutrophication and harmful algal blooms

Eutrophication is a process whereby a water body becomes abundant in aquatic plants and low in oxygen content. It is caused by an increase in nutrients, particularly nitrogen and phosphorus, which can come from fertiliser runoff. Eutrophication can lead to hypoxia, or 'dead zones', where fish and other aquatic life suffocate and die due to a lack of oxygen. This can also cause unpleasant odours.

Eutrophication also encourages the growth of algae, which can produce harmful algal blooms (HABs). These blooms can be toxic and cause rashes, nausea, and respiratory problems in humans, and have been known to kill livestock. They can also be harmful to wildlife and can produce toxins that are dangerous to humans.

The composition of the nutrient pool, as well as the total quantity, impacts HABs. For example, diatoms require silicon for growth, while certain dinoflagellates have a higher phosphorus requirement. The form of the nutrient is also important, as some species can use organic forms of nutrients, while others require inorganic forms.

High-biomass blooms, such as HABs, require a constant input of exogenous nutrients to be sustained. These blooms can be fuelled by an initial injection of nutrients, and then sustained by regenerated nutrients. Nutrient inputs can be either chronic or episodic, and both can promote HAB development.

Management of nutrient inputs to the watershed can lead to significant reductions in HABs. For example, after the removal of sewage discharges from Lake Washington, noxious cyanobacteria blooms declined. Similarly, after improved wastewater treatment and detergent phosphate bans in the early 1980s, nuisance blooms of the green macroalga Cladophora were significantly reduced in Lake Erie.

Impact on human health

Fertilizer pollution in water can have a range of impacts on human health, from infections to serious diseases. Here are some key ways in which fertilizer pollution can affect human well-being:

Blue Baby Syndrome

High levels of nitrates in drinking water are linked to methemoglobinemia, or "blue baby syndrome". This condition primarily affects infants under six months old, causing a bluish skin discoloration around the eyes and mouth due to oxygen depletion. While it is rarely fatal if detected early, it can be life-threatening.

Gastrointestinal Issues

Water contaminated by sewage can lead to gastrointestinal issues such as diarrhea, cholera, dysentery, typhoid, and hepatitis A. According to the World Health Organization (WHO), approximately 1.4 million people die annually due to poor sanitation, hygiene, or unsafe drinking water.

Cancer

Chemical pollutants in water, including pesticides, fertilizers, and heavy metals, pose serious health risks. Ingesting these toxins has been associated with altered brain function, damage to the immune and reproductive systems, and cardiovascular and kidney problems. Arsenic, nitrate, and chromium in drinking water have been linked to skin, kidney, bladder, lung, and liver cancer.

Respiratory Problems

Excessive algae growth, known as algal blooms, can produce toxins that cause respiratory issues in humans. Blue-green algae, in particular, are associated with rashes, nausea, and respiratory problems.

Diabetes

Studies suggest a link between nitrate exposure and an increased risk of type 1 diabetes in children. Nitrates are believed to reduce insulin effectiveness in the body, leading to a build-up of glucose and potentially resulting in ketoacidosis, a life-threatening condition.

Harmful Pathogens

Fertilizer-contaminated water can introduce harmful pathogens, including bacteria, viruses, parasites, and fungi, which can cause various diseases and infections.

The role of nitrogen and phosphorus

Nitrogen and phosphorus are essential nutrients that support the growth of algae and aquatic plants, which provide food and habitat for fish, shellfish, and smaller organisms that live in water. They are natural parts of aquatic ecosystems, and nitrogen is the most abundant element in the air we breathe.

However, when too much nitrogen and phosphorus enter the environment, they can act like fertilizer, causing excessive growth of algae, a process known as eutrophication. This can lead to the development of hypoxic "dead zones", where dissolved oxygen levels are severely reduced or eliminated, resulting in fish kills and a decrease in aquatic life.

Excess nitrogen and phosphorus in water bodies can have far-reaching impacts on public health, the environment, and the economy. Nitrogen-based compounds, such as nitrates, can be harmful to infants, causing a condition known as "blue-baby syndrome" or methemoglobinemia. Additionally, nitrates have been linked to an increased risk of type 1 diabetes and pancreatic cancer in children.

Farmers play a crucial role in managing nitrogen and phosphorus levels. By adopting improved nutrient management techniques, such as applying the right amount of fertilizer at the appropriate time of year and using the correct application method, farmers can significantly reduce the amount of excess fertilizer reaching water bodies.

Waterways and drinking water sources

Excess fertilizer can run off into streams and lakes, contaminating drinking water sources and causing harm to aquatic life and humans. Fertilizer runoff can occur due to heavy rainfall, excessive irrigation, improper yard waste disposal, and the use of too much fertilizer. When fertilizer runs off into waterways, it can cause toxic algal blooms, which can harm aquatic life and people. These algal blooms can create "dead zones" in the water, where fish and other aquatic organisms suffocate due to oxygen depletion.

The chemicals in fertilizers, such as nitrogen and phosphorus, can wash into waterways during rain storms or irrigation events, leading to eutrophication. Eutrophication is the process of excessive nutrient enrichment in a body of water, which disrupts the natural balance of plant life and can lead to the proliferation of undesirable species. High levels of nitrates in drinking water sources can cause "blue baby syndrome" in infants, a condition known as methemoglobinemia, which inhibits the ability of blood to carry oxygen.

To prevent fertilizer runoff from polluting waterways and drinking water sources, it is important to apply fertilizer carefully and in the correct amounts. Keeping fertilizer away from water sources and using slow-release fertilizers can help reduce the risk of nutrient pollution. Additionally, leaving lawn clippings on the ground can return nutrients to the soil and absorb water to prevent runoff.

Preventing fertiliser runoff

Fertilizer runoff can have devastating effects on the environment, including aquatic ecosystems and drinking water sources. However, there are several effective strategies to prevent this issue and protect water sources from pollution.

Preventing Fertilizer Runoff:

• Adopting Nutrient Management Techniques: Farmers can ensure they are using the right amount of fertilizer, at the right time of year, with the right method of application, and in the right location. This can significantly reduce the amount of fertilizer that reaches water bodies.
• Using Conservation Drainage Practices: Implementing strategies such as subsurface tile drainage can help manage water movement through the soil. This prevents nutrient-rich drainage water from reaching and contaminating water sources.
• Ensuring Year-Round Ground Cover: By planting cover crops or perennial species, farmers can prevent soil erosion and nutrient loss during periods when the ground is bare and most vulnerable.
• Planting Field Buffers: Trees, shrubs, and grasses planted along field edges, especially those bordering water bodies, can act as a natural barrier. They absorb or filter out excess nutrients before they reach water sources.
• Implementing Conservation Tillage: Reducing the frequency and intensity of tilling improves soil health, reduces erosion, and minimizes the risk of nutrients reaching waterways through runoff.
• Managing Livestock Access to Streams: Installing fences along water bodies can help keep animals and their waste out of streams, thereby reducing nutrient pollution and protecting stream banks.
• Engaging in Watershed Efforts: Collaboration between farmers, governments, organizations, and community groups is vital. Together, they can implement effective measures to reduce nutrient pollution in water and air.
• Reducing Pesticide Use: By planting various species, using companion planting, and introducing natural predators, farmers can reduce the need for pesticides, minimizing the risk of these chemicals entering water sources.
• Managing Irrigation Systems: Regular maintenance and prompt repair of irrigation systems are essential to prevent leaks and minimize overages that can lead to fertilizer runoff.
• Conservation Tilling Techniques: Techniques such as no-till, in-row subsoiling, strip-tilling, and ridge tilling help minimize soil loss and runoff, reducing the impact on nearby water bodies.
• Contour Farming and Terraces: Planting along the lay of the land uses gravity to direct water flow and improve water efficiency. Terraces, using human-made structures, achieve a similar outcome.
• Water and Sediment-Control Basins: Building berms at the end of slopes prevents water and soil from escaping, conserving water and reducing runoff.
• Grass-Protected Waterways: Grassed waterways provide a path for excess water to flow without causing soil erosion or nutrient loss.
• Streambank and Shoreline Protection: Using physical structures, such as native trees and shrubs, to protect streambanks and shorelines from erosion caused by agricultural runoff.

Frequently asked questions