Farming's Impact: Water Pollution Sources And Solutions

Agriculture is the single largest contributor to non-point-source pollution in surface water and groundwater. It accounts for 70% of total water consumption worldwide. The use of pesticides and fertilisers in agriculture can contaminate both groundwater and surface water, as can organic livestock waste, antibiotics, and processing waste from plantation crops. Contaminated water can have a severe impact on human health and the environment.

Fertilisers and pesticides

The use of fertilisers and pesticides has seen a considerable increase since the 1960s, with about 11 billion kilograms of nitrogen fertiliser and 300 million kilograms of pesticides being used annually to enhance crop production or control pests. The increased levels of nutrients from fertilisers draining into streams can stimulate algal blooms, affecting the health of streams, downstream reservoirs, and estuaries, as well as increasing treatment costs for drinking water. Pesticides transported to streams can pose risks to aquatic life, fish-eating wildlife, and drinking water supplies.

In the United States, agriculture is the leading source of impairments in the nation's rivers and lakes. About a half-million tons of pesticides, 12 million tons of nitrogen, and 4 million tons of phosphorus fertiliser are applied annually to crops. Pesticides have been found in about 94% of water samples and over 90% of fish samples taken from streams across the nation, as well as in nearly 60% of shallow wells sampled.

Livestock waste

Before land application, manure is typically stored in large manure lagoons that can be the size of a football field. These lagoons contain a mixture of antibiotics residue, chemicals, and bacteria, which can overflow or leak, causing the contents to leach into the soil and groundwater. When this mixture, high in phosphorus and nitrogen, reaches a waterbody, it causes eutrophication, or the destructive overgrowth of algae.

Poultry waste, primarily dry litter, is stored in exposed, giant mounds and can also harm waterways due to phosphorus runoff. A study in Lithuania found that pig farms had a more detrimental impact on surface water quality than livestock farms, with an increase in suspended materials, nitrates, and phosphates in the water as the number of pig units increased.

Livestock production is a source of multiple pollutants in rivers. A global multi-pollutant model study found that over 57% of nutrients and oocysts on land are from grazed animal systems, with cattle, pigs, and chickens responsible for 74-88% of these pollutants in rivers.

To reduce water pollution from livestock waste, effective manure management practices are essential. Treating animal waste similarly to human waste by sending it to wastewater treatment plants could help mitigate the environmental impact of livestock farming.

Antibiotics and silage effluents

Antibiotics are used in agriculture to prevent and treat diseases in animals. They can be administered in feed or water, and are used for disease treatment, growth promotion, and the prevention of diseases. Antibiotics are not always fully metabolized and can be released into the environment, including water, manure, or soil. Antibiotics can also be introduced into the environment through soil fertilization with raw animal manure, irrigation with wastewater generated from farm activities, or accidental release by runoffs from farms.

Antibiotics in the environment can lead to antibiotic resistance, which is of great public health concern. Antibiotic-resistant bacteria associated with animals may be pathogenic to humans and can be transmitted to humans through food chains. Antibiotic residues can also have a negative impact on public health and food safety.

The Food and Agriculture Organization of the United Nations (FAO) is working to monitor, control, and mitigate pollution loads from agricultural activities and the negative impacts of agricultural pollution on people's health and the environment.

Processing waste from crops

Nutrient Management Techniques:

Farmers can adopt improved nutrient management practices by carefully controlling the application of fertilizers and animal manure. This involves applying the right amount of nutrients, at the appropriate time of year, using suitable methods, and ensuring proper placement. By optimizing nutrient management, farmers can reduce the risk of excess nutrients reaching water bodies and causing eutrophication, which leads to aquatic dead zones and harmful algal blooms.

Conservation Drainage Practices:

Implementing conservation drainage techniques is essential for managing water movement through soils. This includes strategies such as modifying drainage system design, utilizing woodchip bioreactors, saturated buffers, and making adjustments to the drainage ditch system. By doing so, farmers can reduce nutrient loads, particularly nitrogen and phosphorus, while maintaining adequate drainage for crop production.

Year-Round Ground Cover:

Farmers can plant cover crops or perennial species to prevent bare ground on farm fields. This practice helps protect the soil from erosion and reduces the loss of nutrients into nearby waterways. It ensures that the soil and the nutrients it contains are not easily washed away during rain or snow melt, minimizing their negative impact on water quality.

Field Buffers:

Planting trees, shrubs, and grasses along the edges of fields, especially those bordering water bodies, is an effective strategy. These planted buffers act as natural filters, absorbing or trapping excess nutrients before they reach water bodies. They serve as a natural barrier, reducing the amount of nutrients that can leach into groundwater or surface water.

Conservation Tillage:

Reducing the frequency and intensity of tilling operations can improve soil health and decrease erosion, runoff, and soil compaction. By minimizing soil disturbance, there is a lower likelihood of nutrients being washed away and entering waterways through runoff. Conservation tillage helps in maintaining the structural integrity of the soil while reducing nutrient losses.

Integrated Farming Systems:

Integrated farming approaches, where crops, vegetables, livestock, trees, and fish are collectively managed, offer benefits in terms of waste reduction and resource optimization. In these systems, waste from one component becomes an input for another, helping to close the loop on resource use and minimize pollution. For example, waste from livestock can be used as fertilizer for crops, reducing the need for external inputs.

By implementing these strategies for processing waste from crops, farmers can significantly reduce the impact of their operations on water pollution. These practices contribute to more sustainable agriculture and help protect both the environment and human health.

Use of untreated wastewater

The use of untreated wastewater in agriculture is a pressing issue that has significant implications for water pollution. With the increasing demand for agricultural commodities, farmers are turning to unconventional water sources, including wastewater, to meet their water needs. While this may seem like a viable option, especially in times of conventional water scarcity, the unsafe use of wastewater can lead to severe consequences for the environment and human health.

Wastewater, particularly domestic and municipal wastewater, is known to have a high nutrient content, which can be attractive for farmers aiming to boost crop productivity. However, this wastewater often contains harmful microbiological and chemical pollutants. When used without adequate treatment, these pollutants can accumulate in crops, livestock products, soil, and water resources. This not only degrades the quality of water but also poses severe health risks for consumers and farm workers. The consumption of crops irrigated with untreated wastewater can lead to the ingestion of harmful chemicals and pathogens, potentially causing various health issues.

Moreover, untreated wastewater can exacerbate the problem of antimicrobial resistance. The presence of antibiotics and other pharmaceuticals in wastewater can contribute to the development of antibiotic-resistant bacteria and genes. If these resistant bacteria find their way into our food chain through contaminated crops or livestock, they can pose a significant threat to human health, making it more difficult to treat infections effectively.

In addition to the direct health impacts, the use of untreated wastewater in agriculture can also have indirect effects on the environment. The accumulation of pollutants in the soil can lead to reduced soil quality and productivity over time. Additionally, the untreated wastewater can contaminate nearby water bodies through runoff, affecting aquatic ecosystems and further contributing to water pollution.

However, it is important to note that wastewater, when adequately treated and applied safely, can be a valuable resource for agriculture. Treated wastewater can serve as a source of both water and nutrients, contributing to food security and improving livelihoods. By implementing proper treatment processes and adopting sustainable practices, farmers can harness the benefits of wastewater while minimising its negative impacts on the environment and human health.

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