Reduce Emissions from Cropping Systems and Embrace Climate Smart Agriculture
Environmental Defense Fund
Within agricultural supply chains, cropping systems should be an area of focus for emissions mitigation. According to the EPA, in the US, overuse of nitrogen (N)-containing fertilizer and manure is the primary source of nitrous oxide emissions, accounting for approximately 75% of total U.S. N2O emissions in 2021. Soil tillage, another common agricultural practice, can also contribute to carbon loss from the soil, increasing CO2 emissions. There are many climate-smart agricultural opportunities to reduce emissions in cropping systems in your supply chain.
Companies that actively collaborate with agricultural suppliers to reduce emissions can make significant contributions to building a more resilient supply chain, promoting healthier soil and crops, and adding value through the promotion of climate-smart agricultural products. When addressing agricultural supply chain emissions, it is crucial to prioritize efforts aimed at managing nitrogen application and reducing soil tillage.
Although nitrogen is essential for crop growth, only 40-70% of the nitrogen applied as fertilizer is utilized by the plants.1 The rest, known as “surplus nitrogen,” can be volatilized as ammonia, lost to the air as nitrous oxide, or leached as nitrate in water. These losses cause water and air pollution with harm to human health, wildlife, trees and fish – among other things – and make drinking water sources unsafe for nearby communities.
Tilling the soil to control weeds and help crop seedlings get a good start can also have negative environmental consequences. Soil disturbance can cause soil loss through erosion and release carbon dioxide and nitrogen into the atmosphere, and the combination of heavy machinery and intensive tillage can create compacted, oxygen-deprived conditions that promote methane and nitrous oxide emissions in deeper soils. Improved fertilizer management and other climate-smart agriculture methods that enhance soil health and support ecosystems can help reduce greenhouse gas emissions from crop production systems.
Improve Fertilizer Management
To effectively reduce nitrous oxide emissions within your agricultural supply chain, it is crucial to adopt efficient fertilizer management strategies. When partnering with suppliers and farmers, consider implementing the following mitigation strategies, which include utilizing the N balance metric, employing precision agriculture methods, and integrating natural nitrogen fixation techniques. Detailed descriptions of these fertilizer management strategies are as follows:
- Use N balance: The N balance of a field is a reliable metric for measuring farmers’ risk of nitrogen losses to the environment. It is calculated as the nitrogen added to a farm field minus the nitrogen removed by harvested crops. The remaining nitrogen is vulnerable to being lost to the air as nitrous oxide or into the water as nitrate. By showing where N balance could be improved by practices that could increase yields or require fewer N inputs, this solution focuses on the variables that farmers can control and is calculated with minimal data that is easy for them to gather.
- Apply precision agriculture methods: This approach uses technology (e.g., sensors, GPS mapping, and data analytics) to better track crop health, support integrated pest management practices, make planting decisions, and guide fertilizer and water use to improve the efficiency of farms. Some solutions for optimizing management of nitrogen and other nutrients include variable rate application, remote sensing and crop modeling. Impact can then be evaluated with the N balance metric noted above.
- Consider cultivating nitrogen-fixing plants to reduce synthetic nitrogen fertilizer needs: Legumes are plants that form symbiotic relationships with microbes who convert atmospheric nitrogen into a form that can be used by crops. Legumes include beans, peas, clover, lupines, and alfalfa; which can improve soil health and fertility when used in rotation with other crops or as cover crops in otherwise fallow periods (see below for more on cover crops). Nitrogen-fixing trees could also be an option, but they are more widely used in agroforestry systems.
- Integrate livestock into cropping systems: In some cases, livestock can provide a balanced, organic-matter-rich fertilizer source for crop fields through their manure. By integrating crops and livestock, cutting the distance (and cost) of transporting crops to feed the animals and manure to feed the crops, farmers can recycle the nitrogen and other nutrients from the manure back into the soil, reducing the need for synthetic fertilizers. This also reduces the human health and environmental risks associated with excess nutrients near livestock-raising facilities.
- Invest in research and innovation: Emerging technologies such as artificial intelligence, robotics and automation, biologicals, and genetics can be a promising solution to reduce agricultural greenhouse emissions and minimize other environmental impacts, while also boosting farmers’ yields. To explore more about these opportunities, you can refer to EDF’s Agriculture Discovery Report.
Embrace Climate-Smart Agriculture Methods
To effectively prevent soil loss, which is a significant contributor to carbon emissions in agricultural supply chains, it is crucial to collaborate with your suppliers in investing in climate-smart agriculture methods. These methods aim to maximize soil health, diversify crops, enhance biodiversity, and improve the resilience of farming communities. Below, we highlight the most effective methods:
- Embrace conservation tillage: This climate-smart agriculture method involves reducing the intensity of tilling the soil and can take different forms. Some common practices include no-till drilling, where seeds are planted directly into undisturbed soil; reduced tillage, which reduces tillage passes but still disturbs the soil; and other lower-disturbance tillage methods such as strip-till, where the soil is disturbed only in narrow strips for seed placement.
- Use cover crops: Where feasible, with sufficient water resources and suitable climate, farmers can grow cover crops instead of leaving the ground bare after harvest, as a strategy to capture nitrogen at risk of loss and prevent soil erosion. Cover crops are sometimes called “green manure” because they improve soil health, fertility, and structure when farmers incorporate their plant material into the soil. The most common cover crops in temperate cropping systems include grasses (e.g., rye, oats, wheat), legumes (i.e., beans, peas, lentils), brassicas (e.g., mustard and rapeseed), and buckwheat.
- Support the perennialization of agriculture: This solution emphasizes the use of perennial crops over annual crops. By focusing on crops that regenerate after each harvest such as trees, shrubs, or grasses, farmers can reduce the need for tillage and keep live roots in the ground all year long. Additionally, perennial crops may decrease soil erosion, increase soil health, and reduce greenhouse gas emissions. Researchers are working to develop and improve perennial versions of important crops.
- Incentivize sustainable intensification of diversified food production systems: This concept of sustainable intensification is defined as a process where agricultural yields on the same or less land area are increased without adverse environmental impact, reducing pressure for deforestation or other natural land conversion to agriculture. Diversified food production systems support the production of multiple crops, either at the same time (if sufficient labor resources are available) or in rotation with one another. Greater diversity can provide resilience to climate and market shocks and also support on and off farm biodiversity.
- Innovate with agroforestry: This practice involves integrating trees with crops and/or livestock on the same land area. The trees in agroforestry systems not only absorb and store carbon but can also reduce emissions when the portions of cropland converted into trees receive less fertilizer and require less fuel-intensive cultivation, or if nitrogen-fixing trees help reduce the need for fertilizer. Agroforestry can also contribute to climate change adaptation and local food security (e.g., use of fruit trees) for farming communities, especially in under-resourced regions. Some of the most common methods of agroforestry include: 1) alley cropping: rows of trees or shrubs are planted in between rows of crops; 2) multistrata: an intense method that involves growing multiple layers of trees, shrubs, and crops in the same area (e.g., shade-grown coffee and cocoa); and 3) silvopasture: a method that combines trees, forage, and livestock.