Agriculture's Air Pollution: Strategies For Cleaner Farming

Agriculture is a significant contributor to air pollution worldwide, with food production responsible for a quarter of global greenhouse gas emissions. The use of chemical fertilisers and pesticides has maximised crop yields but has also brought undesirable side effects, including air pollution. However, it is possible to curb the contamination associated with the agricultural sector. This involves adopting sustainable agricultural practices, such as organic farming, precision farming, crop rotation, and agroforestry, as well as implementing measures to reduce emissions and nutrient losses.

Reduce ammonia emissions from livestock manure and chemicals

Livestock manure is a major source of air pollution, contributing to the formation of particulate matter that can be hazardous to human health and damage sensitive ecosystems. To reduce ammonia emissions from livestock manure, it is crucial to incorporate the manure into the soil as quickly as possible. This prevents volatilization losses resulting from exposure to air. Immediate incorporation of surface-applied manure (within 1 hour) can reduce ammonia loss by 85-90%. Even incorporating it within 24 hours is beneficial. Shallow injection and surface banding are effective methods to reduce ammonia emissions compared to broadcast application, which has the highest rates of airborne nitrogen loss.

Additionally, the timing of manure application plays a crucial role in reducing ammonia emissions. Applications during cooler and calmer times of the day, such as in the evening, at night, or in the early morning, can reduce emissions by up to 50% compared to spreading during the middle of the day. Applying manure before light rain, on cool and cloudy days, or during the early morning or evening, will also help minimize ammonia loss.

Another strategy is to apply compost to the land instead of raw manure. Composting results in lower ammonia emissions because NH3 is lost during the composting process, leaving little ammonium in the compost. This eliminates the need for immediate incorporation into the soil, making it suitable for use as a topdressing on perennial crops.

Furthermore, proper waste management on farms is essential. This includes appropriate storage, processing, and disposal of manure and other waste products, as well as recycling and reusing whenever possible.

To reduce ammonia emissions from chemicals, it is important to transition from fossil-fuel-based ammonia (grey ammonia) to green ammonia. Grey ammonia production from fossil fuels generates carbon dioxide as a byproduct, contributing significantly to emissions. Green ammonia, produced using renewable power and electrolysis to create green hydrogen, can almost fully decarbonize ammonia production. This switch has the potential to reduce carbon emissions by an average of 5% in a range of consumer food products.

Minimise chemical drift with pesticides, herbicides, and fertilisers

Minimising chemical drift with pesticides, herbicides, and fertilisers is a crucial aspect of reducing air pollution from agriculture. Chemical drift occurs when these compounds drift away from the intended application site, impacting nearby areas and contributing to poor air quality. Here are some detailed strategies to minimise chemical drift:

Firstly, it is essential to understand the factors influencing drift. Drift is primarily caused by small droplets that remain airborne due to their reduced mass, making them more susceptible to wind forces. Therefore, using nozzles that produce larger droplets can significantly reduce drift. Additionally, the viscosity of the liquid spray solution plays a role; thicker liquids tend to form larger droplets, reducing the potential for drift. Drift retardants can be added to increase viscosity, but their effectiveness may vary.

Secondly, proper calibration and maintenance of application equipment are vital. Calibration ensures consistent output from each nozzle, optimising coverage and minimising drift. Regularly replacing worn nozzles is essential, as they can produce poor spray patterns and droplet distributions, leading to increased drift. Shielding spray booms can also help reduce drift, as it provides a physical barrier to deflect the spray downwards.

Thirdly, applicators should be mindful of weather conditions. High wind speeds can carry droplets over long distances, so applications should be avoided when winds exceed 10 mph. Calm conditions with low wind speeds may indicate the presence of temperature inversions, which trap droplets close to the ground and increase the likelihood of drift. Ideal conditions for spraying are gentle breezes between 3 and 9 mph, blowing away from sensitive areas.

Lastly, implementing buffer zones between the treatment site and sensitive areas is crucial. Buffer zones are untreated areas that act as a safety net to catch any potential drift, protecting nearby vulnerable sites. These zones should be relatively wide and, if possible, contain vegetation or other surfaces to maximise their effectiveness.

By following these strategies, farmers can significantly minimise chemical drift associated with pesticides, herbicides, and fertilisers, contributing to improved air quality and a healthier environment for all.

Improve soil health and reduce erosion

Improving soil health and reducing erosion are key to reducing air pollution from agriculture. Soil is a living, life-giving natural resource, and healthy soil is the foundation of productive, sustainable agriculture.

Reducing Soil Disturbance

Soil disturbance can be caused by hooves, plows, and other means. While some disturbance is unavoidable, minimising it is important for building healthier soils. To reduce soil disturbance, it is recommended to:

• Optimise chemical input.
• Maximise biodiversity.
• Maximise the presence of living roots.

Reducing Tillage

Deep and frequent tillage can create a layer of compacted soil that is vulnerable to water erosion and topped by loose soil that is easily removed by wind. To address this, consider a zero-tillage approach or a ridge-till or mulch-till system that leaves lower soil levels untouched. Conservation tillage techniques also reduce vehicle traffic and, therefore, soil compaction.

Planting Vegetation

Vegetation with deep roots can hold soil in place, especially in areas susceptible to erosion, such as streams, hillsides, and rivers. Vegetative barriers impede water flow due to their thick stems, allowing water to slowly flow through without causing erosion. Native plants with deep roots, such as wildflowers, woody perennials, and native prairie grasses, are ideal for erosion control.

Mulching

Mulching involves covering bare soil to prevent it from being washed away. It is particularly useful in the initial stages of growing seedlings or shrubs, as it conserves moisture and modifies soil temperature. Wood mulch is suitable for gardens, while organic mulches can feed and protect gardens in spring and fall.

Reducing Overgrazing

Grazing too many animals in the same place for a long time can contribute to poor vegetation, leaving soils exposed to water runoff. Rotational grazing and moving livestock through multiple paddocks can reduce erosion, improve forage quality, and allow pasture plant recovery.

Using Plastic Sheeting, Silt Fencing, and Terraseeding

Plastic covers, geotextiles, erosion control blankets, and mats can prevent soil erosion by water or wind, especially for newly planted crops on slopes. Silt fencing, or filter socks, can be used as a temporary barrier to intercept and slow down runoff while retaining sediment-laden runoff. Terraseeding is a method of spreading mixed composted soil with seeds in large areas, reducing the chance of seed disruption.

Improving Drainage

Creating channels for water to flow through can help prevent water from spreading across land and causing erosion. Pipes, gutters, and underground perforated drainage pipes can effectively drain water into water collection systems.

Embracing No-Till Farming

No-till farming leaves the soil structure intact and crop residue on the surface, increasing the soil's ability to infiltrate and absorb water, thereby reducing erosion and runoff.

Building Terraces

Terracing involves levelling off steep sections of a hill into several flat areas, allowing for water absorption and the planting of shrubs and flowers.

Reducing Watering

Excessive watering or irrigation can speed up topsoil erosion. Using less water or investing in a drip irrigation system can help reduce erosion, as drip systems deliver small amounts of water at a time, reducing water flow across the surface.

Adopt nutrient management techniques

Farmers can adopt nutrient management techniques to reduce air pollution from agriculture. Nutrient management techniques involve applying the right amount of nutrients (fertilizer and manure) at the right time of year, with the right method and placement. This can significantly reduce the amount of fertilizer that reaches water bodies and the amount of nutrient losses to the air.

Farmers can apply nutrients in the form of chemical fertilizers and animal manure to provide crops with the nitrogen and phosphorus necessary for growth. However, when plants do not fully utilize nitrogen and phosphorus, they can be lost from farm fields and negatively impact air and water quality. Excess nitrogen and phosphorus can be washed from fields into waterways during rain and snow melt, or leach into groundwater over time. This can cause eutrophication of water bodies, leading to hypoxia ("dead zones") and a decrease in aquatic life.

To improve nutrient management practices, farmers can use precision farming techniques. Precision farming utilizes data on moisture, temperature, humidity, and other parameters to ensure crops receive the exact amount of water and chemicals they require. This not only optimizes resource use but also protects the land from oversaturation with nutrients and toxins.

By adopting nutrient management techniques, farmers can reduce nutrient losses from their operations and minimize air pollution from agriculture.

Use conservation drainage practices

Conservation drainage practices are an important strategy to manage water movement through soils, especially in the Midwest. This is necessary because drainage water can carry soluble forms of nitrogen and phosphorus, which are nutrients necessary for crops to grow and produce food. However, these nutrients can also negatively impact air quality if they are lost from farm fields. Conservation drainage practices aim to reduce nutrient loads while maintaining adequate drainage for crop production.

One such practice is subsurface tile drainage, which involves the use of drainage systems to control water movement on and through soils. Strategies are needed to modify the design and operation of these systems to reduce nutrient loads. This can include the use of woodchip bioreactors, saturated buffers, and modifications to the drainage ditch system.

Another practice is to ensure year-round ground cover by planting cover crops or perennial species. This prevents periods of bare ground on farm fields when the soil and nutrients it contains are most susceptible to erosion and loss into waterways. By keeping the soil covered, conservation drainage practices can help reduce nutrient losses and improve air quality.

In addition, field buffers can be planted with trees, shrubs, and grasses along the edges of fields, especially those bordering water bodies. These buffers can help prevent nutrient loss by absorbing or filtering out nutrients before they reach water bodies and contribute to air pollution.

Conservation tillage is another important practice, which involves reducing the frequency and intensity of tilling fields. This can improve soil health, reduce erosion, runoff, and soil compaction, and decrease the chance of nutrients reaching waterways through runoff.

By implementing these conservation drainage practices, farmers can play a crucial role in reducing air pollution while still maintaining productive crop yields.

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