Kiera Jefferson
Agriculture is a leading cause of water pollution, with farming practices discharging contaminants such as agrochemicals, organic matter, drug residues, sediments, and saline drainage into water bodies. The use of pesticides and fertilizers in agriculture can contaminate both groundwater and surface water, as can organic livestock waste, antibiotics, and processing wastes from plantation crops. Livestock manure is a significant contributor to air pollution, and when washed into water bodies, it can cause beach and shellfish bed closures and affect drinking water supplies. In addition, the unsafe use of wastewater in agriculture can lead to the accumulation of microbiological and chemical pollutants in crops, livestock products, and soil and water resources, posing severe health risks to exposed food consumers and farm workers.
What You'll Learn
Pesticides, antibiotics, and other agrochemicals
Pesticides are a class of chemicals used in agriculture to kill or control pests. They include herbicides (for weeds), insecticides (for insects), fungicides (for fungi), nematocides (for nematodes), and rodenticides (vertebrate poisons). Pesticides can contaminate water through runoff from fields and storage areas, as well as spray drift from aerial and ground applications. The unique properties and stability of individual pesticides determine the specific risk they pose to water sources. For example, the widely used herbicide atrazine has been banned in Europe due to its pollution of water sources and its ability to alter the genetic characteristics of frogs, causing male frogs to develop female organs.
Antibiotics, while not directly used in agriculture, are administered to livestock to prevent diseases and promote growth. They can enter water sources through agricultural runoff and wastewater from households, hospitals, and pharmaceutical companies. Antibiotics in water can lead to the development of antibiotic-resistant bacteria and genes, which can be harmful to human health.
Other agrochemicals, such as fertilizers, can also contribute to water pollution. Excess fertilizer use has been linked to nitrate pollution in water bodies, exceeding safe drinking water limits set by the World Health Organization (WHO). This type of pollution can occur through fertilizer runoff from agricultural fields, impacting both groundwater and surface water sources.
The use of agrochemicals in agriculture has increased significantly over the decades, with a reported 1000% increase in fertilizer applications and a 325% increase in pesticide use in the Philippines between specific years. However, this increase in chemical input has not resulted in a proportional increase in crop yields, calling into question the sustainability and effectiveness of this model of agricultural growth.
To address the issue of water pollution from pesticides, antibiotics, and other agrochemicals, it is essential to reduce the reliance on these chemicals in agriculture. This can be achieved by promoting sustainable and organic farming practices, as well as implementing regulations and programs to reduce agrochemical use, as suggested by organizations like Greenpeace. Additionally, improving wastewater treatment technologies to effectively remove pollutants like antibiotics is crucial to protecting water sources and human health.
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Livestock and manure
Livestock and their manure are significant contributors to water pollution from agricultural activities. The United States alone produces nearly 1.4 billion tons of manure from livestock and poultry annually, almost five times the waste of the entire US population. This waste is often spread on the land untreated, leading to runoff into water sources.
The large volume of manure produced means that it is often stored in vast manure lagoons before being applied to the land. This practice, along with the direct application of manure to the land, can result in runoff into water bodies, contributing to water pollution. Storing manure in covered stockpiles or protected upland areas can help to minimize runoff risks.
Nutrient management practices, such as soil testing and crop-specific calibration, can also help to minimize runoff by targeting fertilizer and manure application and maximizing uptake. Additionally, using drip irrigation instead of furrow irrigation allows for better control of the amounts of pesticides and nutrients added to irrigation water.
Livestock manure contains nutrients and bacteria that can degrade water quality when they enter water bodies. Increased levels of nitrogen and phosphorus from manure can stimulate algal blooms in lakes and rivers, leading to hypoxic (low oxygen) conditions that are harmful to aquatic life. Bacteria from manure can also contaminate water sources, leading to beach and shellfish bed closures and affecting drinking water supplies.
Furthermore, the production of livestock feed, typically grown using pesticides and fertilizers, contributes to water pollution. Planting crops like legumes can help sequester more nitrogen in the soil, whereas composting cow manure releases methane and nitrous oxide, contributing to greenhouse gas emissions.
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Fertilizer runoff
Agriculture is the primary source of pollution in streams and rivers in the US, and it is also a significant contributor to water contamination in lakes and wetlands. One of the main ways that agriculture pollutes water is through fertilizer runoff.
Fertilizers are applied to crops to provide essential nutrients like nitrogen, phosphorus, and potassium, which promote plant growth and increase yields. However, when too much fertilizer is applied, or when it is not applied properly, it can be washed away from fields and into nearby waterways during rain or irrigation. This process is known as fertilizer runoff, and it can have significant environmental and health impacts.
In addition to eutrophication, fertilizer runoff can also lead to the bioaccumulation of toxic chemicals in aquatic organisms, which can be passed up the food chain through a process known as biomagnification. This poses risks not only to aquatic species but also to predators, including birds and humans, who consume contaminated fish. For example, the Great Barrier Reef has suffered extensive damage from agricultural runoff, with pesticides, herbicides, and excess nutrients flowing into the marine environment and disrupting the delicate ecological balance.
To mitigate the impacts of fertilizer runoff, farmers can implement a range of conservation practices. These include adopting nutrient management techniques, such as applying fertilizers in the proper amounts and at the right time of year, using buffer zones and vegetative strips to trap sediment and absorb nutrients before they reach water bodies, and implementing conservation tillage to reduce erosion and runoff. By implementing these practices, farmers can help to minimize the environmental and health risks associated with fertilizer runoff and improve the overall health of aquatic ecosystems.
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Soil erosion and sedimentation
Excessive sedimentation from erosion can overwhelm and smother aquatic ecosystems, including coral reefs. The sediment can cover breeding areas, reducing the ability of fish and other aquatic organisms to reproduce. This can lead to a decline in populations of aquatic species and disrupt the natural balance of the ecosystem.
Agricultural practices that contribute to soil erosion include improper land management, such as excessive tilling and monocropping without adequate erosion control measures. The removal of vegetation cover, such as through deforestation for agricultural land expansion, also leaves the soil more vulnerable to erosion by wind and water.
Controlling soil erosion and reducing sedimentation in water bodies is essential for maintaining the health of aquatic ecosystems. Conservation practices such as contour strip cropping, terracing, and implementing buffer strips can help reduce erosion and sedimentation rates. These practices can trap sediment before it enters water bodies, allowing it to be deposited more slowly downstream or in less ecologically sensitive areas.
Additionally, the use of certain agricultural inputs, such as fertilizers and pesticides, can further exacerbate the problem of sedimentation. When these chemicals are applied to fields, they can increase the solubility of soil particles, making them more prone to erosion and subsequent transport to water bodies. Therefore, addressing the issue of soil erosion and sedimentation in agriculture is crucial for mitigating the negative impacts on water quality and aquatic ecosystems.
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Wastewater and water reuse
Agriculture is a major contributor to water pollution. Agricultural chemicals move into and through every component of the hydrologic system, including air, soil, soil water, streams, wetlands, and groundwater. The National Water Quality Assessment shows that agricultural runoff is the leading cause of water quality impacts to rivers and streams, the third-largest source for lakes, and the second-largest source of impairments to wetlands.
Water reuse in agriculture refers to the use of recycled water in agricultural settings, including irrigation of food crops, non-food crops, and animal feed. Water reuse has the potential to alleviate water scarcity and boost food production. Common sources of water for reuse in agriculture include municipal wastewater facilities, water reclamation facilities, and processing plants for agricultural products.
Treated wastewater (TW) reuse for irrigation could alleviate water imbalances and boost food production in water-scarce regions, promoting global food and water security. TW reuse for irrigation could also act as a major contributor to a circular economy and sustainable development. However, the first steps will be funding and implementing advanced and sustainable treatment technologies and social acceptance. Over 80% of global wastewater is discharged untreated, and this untreated wastewater is sometimes used directly or indirectly for the production of potentially contaminated feed or food.
Advanced water treatment and reuse schemes, supported by water quality monitoring and regulations, can provide a safe and stable water supply for agricultural production. Such schemes could potentially serve as a net energy source, as the embedded energy in wastewater exceeds treatment needs by 9 to 10 times.
Several successful water reuse projects have been implemented in the United States. For example, the City of John Day replaced its aging wastewater treatment plant with a facility that uses hydroponic technology for beneficial reuse, growing vegetables in nutrient-fortified recycled water. In another instance, the coalition including the City of Orlando, Orange County, and the region's agricultural community have worked to irrigate up to 2,737 acres of citrus annually with recycled water.
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Frequently asked questions
Agriculture pollutes water through the use of pesticides and fertilizers, which can contaminate both groundwater and surface water. Livestock waste, antibiotics, silage effluents, and processing wastes from plantation crops are also contributing factors.
Increased levels of nitrogen and phosphorus from fertilizers and manure can stimulate algal blooms in lakes and rivers, which can lead to low-oxygen conditions that are harmful to aquatic life. Pesticides can also pose risks to aquatic life, fish-eating wildlife, and drinking water supplies.
Livestock farming contributes to water pollution through manure, which contains high levels of phosphorus and can harm waterways through phosphorus runoff. Manure also emits ammonia, which combines with other air pollutants to create harmful solid particles that can cause heart and lung diseases in humans.
Agriculture accounts for 70% of water withdrawals worldwide, making it the largest consumer of water. The unsafe use of wastewater in agriculture can lead to the accumulation of microbiological and chemical pollutants in crops, livestock products, and water resources, which can have severe health impacts on consumers and farm workers.
