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Agricultural pollution

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Agricultural pollution refers to the contamination of ecosystems caused by the byproducts of farming. These byproducts can be biotic, which are living, or abiotic, which are non-living. This pollution can degrade the environment and harm human health or economic interests. It often occurs through point source pollution, which comes from a single discharge point. It also occurs as non-point source pollution, which is more diffuse across a landscape.

Water pollution in the Wairarapa
Water pollution in the Wairarapa

The mechanism of pollution often involves the movement of substances through the environment. For example, pesticide leaching occurs when aqueous solutions move to off-target sites. This process is influenced by soil texture, rainfall, and irrigation levels. Water-soluble pesticides are especially prone to leaching into groundwater. This can happen in sandy soils or when excessive watering occurs right after application. Leaching can also originate from pesticide mixing areas or machinery washing sites.

One major type of agricultural pollution involves the use of pesticides. While these chemicals prevent crop losses of about 40 percent, they can be very persistent. Some chemicals, like 2,4-D and atrazine, have lifetimes of up to 20 years. Other substances like DDT and aldrin are also long-lived. These pesticides can accumulate in animals that eat contaminated soil organisms. Biopesticides, which are derived from natural sources, are used to reduce pollution, but they often face similar negative impacts as synthetic versions.

Fertilizer use is another significant source of pollution, specifically through nitrogen and phosphorus. Nitrogen fertilizers, such as nitrate (NO3−) and ammonium (NH4+), increase crop yields but can cause eutrophication. This process creates hypoxic or anoxic conditions, which are low or no-oxygen environments that can be deadly to aquatic species. Nitrate levels above 10 mg/L in groundwater can cause "blue baby syndrome" in infants. Nitrogen can also release NH3 gases or N2O, a greenhouse gas that may destroy stratospheric ozone.

Anaerobic Lagoon at Cal Poly
Anaerobic Lagoon at Cal Poly

Phosphorus is another essential nutrient that can cause environmental disruption. Most phosphorus is applied as phosphate (PO43-) through synthetic salts, manure, or compost. Because phosphorus is often a limiting nutrient, even small amounts can trigger massive algae and cyanobacteria blooms. These blooms can produce cyanotoxins that harm humans, animals, and aquatic life. Additionally, the phosphate rock used in fertilizers may contain cadmium or fluoride. Continuous use of high-cadmium fertilizer can contaminate soil and plants.

Yellow star thistle
Yellow star thistle

Animal agriculture and physical waste also contribute to environmental degradation. Manure management is critical, as bacteria and pathogens in manure can reach streams if storage in lagoons is poorly managed.

Anaerobic Lagoon at Cal Poly
Anaerobic Lagoon at Cal Poly

Farming also generates massive amounts of plastic waste. A 2021 FAO study estimated that 10 million tons of agricultural plastic waste are produced annually. This includes plastic sheeting for greenhouses and mulch. Much of this plastic is never collected and remains in the landscape.

Litter from plastic balage wrappings
Litter from plastic balage wrappings

Land management practices directly affect soil health and stability. Intensive management can lead to soil erosion and sedimentation. It is estimated that agricultural land degradation causes an irreversible decline in fertility on about 6 million hectares of fertile land every year.

Soil erosion - geograph.org.uk - 1135515
Soil erosion - geograph.org.uk - 1135515

Furthermore, farm machinery can introduce chemical contamination through oil spills or hydraulic fluid leaks. Addressing these various pollutants is a central goal for developing a sustainable food system and mitigating climate change.

Cropduster spraying pesticides
Cropduster spraying pesticides
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🖼️ Images & Media (7)
File:Water pollution in the Wairarapa.JPG
Water pollution in the Wairarapa.JPG
File:Cropduster spraying pesticides.jpg
Cropduster spraying pesticides.jpg
File:Litter from plastic balage wrappings.JPG
Litter from plastic balage wrappings.JPG
File:Soil erosion - geograph.org.uk - 1135515.jpg
Soil erosion - geograph.org.uk - 1135515.jpg
File:Yellow star thistle.jpg
Yellow star thistle.jpg
File:Bt plants.png
Bt plants.png
File:Anaerobic Lagoon at Cal Poly.jpg
Anaerobic Lagoon at Cal Poly.jpg
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