Agricultural pollution

Agricultural pollution is a big problem that happens when farming can hurt the environment and living things. It comes from many places, like water that flows from one spot or pollution that spreads out over a wide area. This pollution can damage wildlife, make drinking water unsafe, and even create areas in the water where very little can live, called dead zones.

Water pollution due to dairy farming in the Wairarapa area of New Zealand (photographed in 2003)

The way people farm affects how much pollution happens. Things like how animals are kept, how fields are plowed, and using too much fertilizer or pesticides can all cause problems. When these things are not done carefully, pollution can get into lakes, rivers, wetlands, and even the water under the ground.

Pollution from farming also affects the air, especially through changes in how land is used and how animals are raised. This can help change the climate and make the Earth warmer. Taking care of these pollution problems is very important for making sure we can grow food in a way that is good for the planet.

Abiotic sources

Pesticides

Fertilizers

Fertilizers give crops nutrients to grow better, but they can also harm people and nature. A big problem is eutrophication, where too many nutrients cause too much growth of plants and algae in water.

Nitrogen and phosphorus are common nutrients in fertilizers. They help farms produce more food, but when they wash off fields, they can pollute rivers, lakes, and groundwater. Too much nitrogen in water can make it unsafe for babies and can harm wildlife. Nitrogen can also get into the air, causing acid rain and other problems. It can even damage soil and change which plants and animals live there.

Phosphorus

Further information: Phosphate fertilizer

Phosphorus is another important nutrient, but using too much can also harm water supplies. Even small amounts can cause big changes in water ecosystems, leading to harmful algae growth that can hurt animals and people.

Hale bales on the side of the road that were covered in protective plastic. Some of the used plastic has been left on the side of the road, as plastic waste, that can break down in the environment.

From equipment and agricultural plastics

Further information: Agricultural machinery and Plastic in agriculture

Farm machines can release harmful gases and cause spills of oils or fluids. Plastics used on farms, like sheets for greenhouses or bags for feed, also add to pollution. A lot of plastic from farms is never collected, adding to the problem of plastic waste.

Land management

Soil erosion and sedimentation

Soil erosion: soil has washed from a ploughed field through this gate and into a watercourse beyond.

Farming can cause soil to wash away, especially when land isn’t managed well. This soil can end up in rivers and lakes, making the water cloudy and harming animals that live there. It can also carry pollutants like phosphorus and pesticides into the water.

Tillage and nitrous oxide emissions

The way farmers work their soil can change how much nitrous oxide, a powerful greenhouse gas, is released into the air.

Organic farming and conservation agriculture in mitigation

Organic farming

Conservation agriculture

Conservation agriculture tries to keep soil healthy by not disturbing it too much, using mulch or cover crops, and growing different kinds of plants. This helps reduce the need for fertilizers, which cuts down on harmful emissions and keeps soil stable.

Biotic sources

Organic contaminants

Manures and biosolids can be valuable as fertilizers, but they may also contain unwanted materials, including certain chemicals used by animals.

Greenhouse gases from fecal waste

The United Nations Food and Agriculture Organization found that about 18% of human-made greenhouse gases come from livestock, either directly or indirectly. Some believe this number might be higher, up to 51%, due to older data used in the study. Even at 18%, livestock are a major source of these gases.

A study showed that removing all animals from U.S. farming would only lower greenhouse gas emissions by about 2.6%. This is because we would need to find other ways to replace nutrients and products from animals, and we would still face challenges with obesity from extra energy intake.

Introduced species

Centaurea solstitialis, an aggressively invasive weed, was probably introduced to North America in contaminated fodder seed. Agricultural practices such as tilling and livestock grazing aided in its rapid spread. It is toxic to horses, prevents native plants from growing (decreasing biodiversity and degrading natural ecosystems), and is a physical barrier to the migration of indigenous animals.

Invasive species

As farming spreads worldwide, it sometimes carries unwanted plants, pests, and diseases to new places. If these settle in, they can harm local wildlife and affect farming. For example, moving bees from Europe to North America brought a parasite that may have hurt native bees. Farming activities can also make it easier for these invaders to take hold. Contaminated equipment, animals, or seeds can spread unwanted plants.

Countries have rules to stop the spread of harmful invaders. In the United States, the Department of Agriculture works to control these species at borders and ports.

Biological control

Using natural enemies like parasites to control pests can reduce the need for chemicals. However, introducing these controls from other places can sometimes harm local wildlife if they attack native species. Careful testing and rules help prevent unwanted effects.

Genetically modified organisms (GMO)

Genetic contamination and ecological effects

GMO crops can sometimes mix with wild plants, potentially changing them or making weeds stronger. There are also worries that GMO plants could harm helpful insects like bees or butterflies. For example, some corn can affect monarch butterflies if nearby plants are dusted with its pollen.

Using GMO crops that resist weeds can also lead to more weed-killing chemicals being used, which can harm plants like milkweed that butterflies need.

GMO as a tool of pollution reduction

GMOs might also help reduce pollution from farming. For example, some genetically changed pigs can better digest nutrients from their food, reducing waste that can pollute soil.

Animal management

Manure management

Animal waste is a big source of pollution for air, soil, and water. Farms in the United States produce huge amounts of waste, much more than human sewage plants. This waste can pollute groundwater with too much nitrogen and can harm rivers when rain washes it away. Managing this waste properly helps reduce pollution and protect health.

Anaerobic lagoon at a dairy

Manure treatment

Composting

Composting is a way to manage solid animal waste by letting it break down naturally. There are two types: active, where the waste is stirred, and passive, where it is left alone. Passive composting produces fewer greenhouse gases.

Solid-liquid separation

Waste can be separated into solids and liquids. The liquid can be easily spread on fields, while the solid part can be used as bedding or composted.

Anaerobic digestion and lagoons

Anaerobic digestion uses bacteria to break down liquid waste without air, creating biogas that can be used for heat or electricity. Lagoons are slower ways to break down waste using similar processes but work best in warmer climates. Both methods help reduce smells and greenhouse gases.