Agricultural pollution

Agricultural pollution is a 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 and make drinking water unsafe.

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. 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 help crops grow, but they can also harm people and nature. Too many nutrients can cause too much growth of plants and algae in water.

Nitrogen and phosphorus are common in fertilizers. When they wash off fields, they can pollute rivers, lakes, and groundwater. Too much nitrogen can be unsafe for babies and harm wildlife. Nitrogen can also get into the air, causing problems like acid rain. It can damage soil and change which plants and animals live there.

Phosphorus

Further information: Phosphate fertilizer

Phosphorus is important, but using too much can harm water supplies. Even small amounts can cause big changes in water, 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. Plastics used on farms, like sheets or bags, also add to pollution. A lot of farm plastic is never collected, adding to 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 if land isn’t managed well. This soil can end up in rivers and lakes, making the water cloudy and harming animals. It can also carry pollutants 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 keeps 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, cutting down on harmful emissions and keeping soil stable.

Biotic sources

Organic contaminants

Manures and biosolids can be good fertilizers, but they might have unwanted chemicals from animals.

Greenhouse gases from fecal waste

The United Nations Food and Agriculture Organization says that about 18% of greenhouse gases made by humans come from livestock. Some think this number could be higher. Even so, livestock are a big source of these gases.

A study showed that taking all animals out of U.S. farming would only lower greenhouse gas emissions by about 2.6%. This is because we would need other ways to get nutrients and products from animals.

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 grows around the world, it can carry unwanted plants, pests, and diseases to new places. If they stay, they can harm local wildlife and farming. For example, moving bees from Europe to North America brought a parasite that may have hurt native bees. Farming can also help these invaders spread. Dirty equipment, animals, or seeds can move 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 mean using fewer chemicals. But, bringing these controls from other places can sometimes harm local wildlife if they attack native species. Testing and rules help prevent unwanted effects.

Genetically modified organisms (GMO)

Genetic contamination and ecological effects

GMO crops can sometimes mix with wild plants, possibly 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 might affect monarch butterflies if nearby plants get its pollen.

Using GMO crops that resist weeds can 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 can pollute air, soil, and water. Farms in the United States make a lot of waste, 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 makes fewer greenhouse gases.

Solid-liquid separation

Waste can be separated into solids and liquids. The liquid can be spread on fields easily, 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, making 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.