Fertilizer Runoff: A Natural Water Pollution Concern?

Fertilizers are a major source of water pollution, causing eutrophication, a process that speeds up the natural growth of algae and depletes oxygen levels in water bodies. Excess nutrients, primarily nitrogen and phosphorus, from fertilizers enter water bodies through runoff during storms and irrigation, leading to uncontrolled algae blooms that discolor the water and create dead zones where aquatic life cannot survive. This has costly impacts on the environment, economy, and public health, with many cities banning the use of chemical fertilizers near water bodies. While fertilizers contribute to increased crop yields, their improper management leads to negative consequences for plant and animal life, including humans.

Nitrogen and phosphorus runoff from fertilizers

Nitrogen and phosphorus are essential nutrients that promote plant growth. They are typically applied to farm fields in the form of chemical fertilizers and animal manure. However, when these nutrients are not fully utilized by growing plants, they can be lost from farm fields and negatively impact water quality. This can occur when nitrogen and phosphorus are washed from farm fields into nearby waterways during rain and snowmelt events, or when they leach through the soil and into groundwater over time.

The impact of nitrogen and phosphorus runoff extends beyond the aquatic environment. As the algae decay, they produce toxins that can be harmful to humans and wildlife. High levels of nitrate in water, resulting from nutrient pollution, pose a danger to both animals and humans. Consumption of water with elevated nitrate concentrations can lead to health issues such as methemoglobinemia, or "blue baby syndrome", in infants. Additionally, the emission of odours and gases into the air can occur due to the presence of excess nutrients in water.

To mitigate the adverse effects of nitrogen and phosphorus runoff, it is crucial to adopt improved nutrient management practices. This includes applying nutrients in appropriate amounts, at the right time of year, and with suitable methods and placement. Implementing conservation tillage practices can help reduce soil erosion and runoff, thereby decreasing the likelihood of nutrients reaching waterways. Additionally, farmers can utilize conservation drainage techniques to manage water movement and reduce nutrient loads while maintaining adequate drainage for crop production.

Eutrophication and algal blooms

Eutrophication is a type of pollution caused when excess nutrients, primarily nitrogen and phosphorus, enter a water body. This overload of nutrients causes an explosion in algae growth, which depletes the water of oxygen as the algae die. This phenomenon, known as hypoxia, results in oxygen levels becoming so low that aquatic life can no longer survive, creating "dead zones".

Excess nutrients from fertilizers can enter water bodies through runoff, which carries the nutrients across lawns, roads, and woods into ditches and streams that eventually run into larger bodies of water. This runoff can come from sources such as lawn fertilizers, agricultural fields, golf courses, or manure applications. The introduction of even small amounts of these nutrients can significantly increase the production of aquatic plants and algae, which is not healthy for water resources.

Algal blooms are a direct result of eutrophication. The fast growth of certain algae leads to the production of toxins, creating toxic conditions in lakes and oceans. In freshwater, cyanobacteria are the primary toxin producers. While algae do produce toxins naturally to protect themselves from being eaten, the uncontrolled growth of algae due to nutrient pollution from fertilizers or untreated wastewater results in the harmful conditions seen during algal blooms.

The consequences of algal blooms include the depletion of oxygen in surface waters, the presence of pathogens and nitrates in drinking water, and the emission of odours and gases into the air. High levels of nitrates can be dangerous for both humans and animals, with the potential to cause health issues in pregnant women, infants, and those with gastric issues. Algal blooms can also reduce the recreational value of waterways and negatively impact the value of surrounding properties.

Impact on aquatic life and humans

Fertilizer pollution in water has a detrimental impact on aquatic life and humans. Excessive fertilizer use and subsequent nutrient runoff can lead to eutrophication, causing an abundance of nutrients in water bodies and disrupting the natural balance of aquatic plant life. This process, known as eutrophication, results in the rapid and harmful growth of algae and other aquatic plants, leading to the formation of algal blooms. These blooms can discolor water bodies and produce unpleasant odors. More importantly, they contribute to the depletion of oxygen in the water, creating "dead zones" where aquatic life, such as fish, cannot survive. This phenomenon, known as hypoxia, has severe consequences for aquatic ecosystems.

The chemicals in fertilizers, including nitrogen, phosphorus, and potassium, are a significant source of water pollution. When fertilizers are improperly applied to lawns, they can easily wash into local streams and reservoirs, impacting the health of aquatic organisms. Additionally, the runoff from fertilizers can pick up other pollutants, such as sediment, microbes, pesticides, and heavy metals, further contaminating water sources.

The presence of nitrates in fertilizer runoff poses a significant risk to both aquatic life and humans. High nitrate levels in water can be toxic to fish and other aquatic organisms. In humans, consuming water with elevated nitrate concentrations can lead to methemoglobinemia, commonly known as "blue baby syndrome," in infants. It can also cause health issues in pregnant women and individuals with gastric problems.

Furthermore, fertilizer pollution contributes to the growth of seaweed, which, while not producing toxins like cyanobacterial algae, can choke out other organisms by competing for resources. This disruption in the natural balance of aquatic life can have far-reaching consequences for the entire ecosystem.

To mitigate these impacts, proper fertilizer management is crucial. This includes applying only the necessary type and amount of fertilizer, using appropriate application methods, and avoiding fertilization during specific periods when the nutrients are more likely to run off into water bodies. By adopting environmentally conscious practices, we can minimize the negative effects of fertilizer use on aquatic life and humans.

Sources of fertilizer pollution

Fertilizers are a source of nutrients for plants, providing them with nitrogen, phosphorus, and potassium, as well as other micronutrients such as zinc, iron, manganese, and copper. However, when fertilizers are mismanaged or overused, they can become a source of pollution, particularly for water bodies.

Phosphorus in Fertilizers

Phosphorus is a nutrient that is present in fertilizers and is essential for plant growth. However, when excess phosphorus from fertilizers enters water bodies, it contributes to poor water quality. This can occur through fertilizer runoff, where the excess phosphorus is carried by stormwater or irrigation across lawns, roads, and woods into ditches and streams, which eventually flow into larger water bodies such as reservoirs, lakes, bays, or the ocean. The phosphorus acts as a nutrient source for algae, leading to uncontrolled algae blooms that reduce water clarity and deplete oxygen levels in the water, creating hypoxic or anoxic conditions that are detrimental to aquatic life.

Nitrogen in Fertilizers

Nitrogen is another key nutrient in fertilizers that is crucial for plant growth. However, when excess nitrogen is present in water bodies, it can lead to eutrophication, a process where the water becomes abundant in aquatic plants and depleted of oxygen. This results in hypoxic or "dead zones," causing fish kills and a decline in aquatic life. Additionally, high levels of nitrogen in the form of ammonia can be toxic to fish and other aquatic organisms, even at low concentrations.

Manure as Fertilizer

Animal manure is commonly used as a fertilizer in agriculture, providing crops with nitrogen and phosphorus. However, when not properly managed, manure can contaminate water sources through bacterial contamination of groundwater, particularly near wells. Manure can also impact surface water quality, introducing pathogens and high levels of nitrates, which can be harmful to both human and animal health.

Agricultural Practices

The application of fertilizers in agriculture can contribute to water pollution if not properly managed. Excess fertilizer can be washed away from fields during rain or snowmelt and enter nearby waterways, leading to nutrient pollution. This is particularly common with nitrogen and phosphorus, which can negatively impact downstream water quality and contribute to eutrophication and algal blooms.

Manufacturing and Air Pollution

The manufacturing process of fertilizers can also be a source of pollution. During production, polluting gases such as ammonia, nitrogen oxides, sulphur oxide, and volatile solvents are emitted into the air. These gases can have detrimental effects on both the environment and human health, contributing to respiratory issues, circulatory system disorders, and organ damage.

Preventing fertilizer water pollution

Fertilizers are a significant source of nutrient pollution in water bodies. Excessive use of fertilizers and subsequent nutrient runoff can impact water bodies, including locally. This can cause an overload of nutrients in the water, leading to uncontrolled algae growth, which depletes the water of oxygen, creating anoxic conditions where no aquatic life can survive. This phenomenon is called hypoxia, and it can also stress aquatic life.

• Adopting Nutrient Management Techniques: Farmers can improve nutrient management practices by applying the right amount of fertilizer at the right time of year, with the right method and placement. This ensures that the plants fully utilize the nutrients, reducing the risk of excess nutrients being washed away into nearby water bodies.
• Conservation Drainage Practices: Implementing strategies such as subsurface tile drainage, modifying drainage system designs, and using saturated buffers can help manage water movement and reduce nutrient loads while maintaining adequate drainage for crop production.
• Preventing Runoff: Avoid applying fertilizer near water bodies to prevent runoff into lakes, streams, or ponds. This includes keeping animal waste away from streams to reduce nitrogen and phosphorus levels in the water.
• Cover Crops and Ground Cover: Planting cover crops or perennial species can prevent soil erosion and reduce the risk of bare ground, which is more susceptible to erosion and nutrient loss.
• Fencing and Watershed Efforts: Installing fences along water bodies can help block livestock access, restore stream banks, and prevent excess nutrients from entering the water. Collaborating with various stakeholders and organizations across a watershed can also help reduce nutrient pollution.
• Humus Conversion: Increasing the soil's ability to absorb and retain water through humus conversion can reduce runoff and fertilizer loss.
• Proper Application: Apply fertilizers only when needed, during the proper season, and in the correct amounts. Avoid applying fertilizers to areas where runoff is more likely, such as driveways, sidewalks, and storm drains.
• Mulching and Mowing: On lawns, use a mulching mower and cut no more than the top third of the grass. Leaving lawn clippings to decompose can return valuable nutrients to the soil and reduce the need for fertilizer.
• Soil Erosion Prevention: Cover the ground with vegetation or mulch to prevent soil erosion and reduce the loss of fertilizer due to erosive forces.
• Manure Management: Avoid surface application of manure near wells or drinking water supplies to prevent bacterial contamination of groundwater. When grazing livestock near surface water sources, restrict their access to prevent manure from impairing water quality.

Frequently asked questions