Reducing Nitrogen Loss: Minimizing Nitrous Oxide & Ammonia Emissions from Fertilizers

Nitrogen Fertilizer Use Linked to Significant Greenhouse Gas Emissions

The application of nitrogen-based fertilizers, while crucial for crop production, is a significant contributor to the release of nitrous oxide (N2O), a potent greenhouse gas, according to recent research and data released by German agricultural scientists. While efforts to reduce ammonia emissions through improved fertilizer practices are underway, studies indicate these methods can inadvertently increase N2O and dinitrogen (N2) emissions by as much as 800 percent.

Nitrous oxide possesses a global warming potential 265 times greater than carbon dioxide, making even small increases in its atmospheric concentration a concern. The gas is produced naturally in soils through a process called denitrification, where nitrate is converted to molecular nitrogen under low-oxygen conditions. This process, essential for nutrient cycling, also generates N2O as an intermediate byproduct.

Researchers have found that the amount of N2O released isn’t solely dependent on the type of fertilizer used, but also on specific local conditions, including soil moisture, and aeration. The Intergovernmental Panel on Climate Change (IPCC) provides Emissions Factors (EFs) to estimate greenhouse gas releases, with current figures indicating a 1.6 percent EF for mineral fertilizers and 0.6 percent for organic fertilizers in wet soils. These figures drop to 0.5 percent for both fertilizer types in dry or arid conditions.

While incorporating liquid organic fertilizer into the soil is often recommended to reduce ammonia emissions, recent findings suggest this practice can exacerbate N2O and N2 emissions. What we have is particularly problematic in waterlogged or poorly drained soils, where anaerobic conditions favor N2O production. Experts advise against applying nitrate-containing fertilizers to saturated or waterlogged soils to mitigate these losses.

Even when losses are minimized, they can still be substantial. Typical N2O losses range from 1 to 2 kg of nitrogen per hectare. Given the potency of N2O as a greenhouse gas, even these seemingly small losses can have a significant climate impact.

Ammonia losses also present a challenge. These occur primarily when urea is converted to ammonium, a process that sharply increases the pH level around the fertilizer granule. This pH increase shifts the chemical equilibrium, favoring the formation of gaseous ammonia. The amount of ammonia lost can range from a few percent to approximately 10 percent of the applied nitrogen, depending on factors like temperature, soil moisture, pH, and application methods.

Several strategies can be employed to reduce ammonia losses from mineral fertilizers. Some urea-based fertilizers available on the market incorporate urease inhibitors, which slow down the conversion process and reduce ammonia volatilization, potentially exempting them from mandatory urease inhibitor requirements or incorporation practices.

nitrogen losses represent both an economic cost for farmers and an environmental burden. Utilizing appropriate fertilizers and employing best management practices can effectively reduce these gaseous losses, but ongoing research and monitoring are crucial to refine these strategies and minimize the impact on the climate.