AIR: How does nitrogen use efficiency affect greenhouse gas emissions?
Over the past four years, we have been working with farmers interested in measuring and documenting the sustainability of their farming operations and what they can do to improve their production system. In the next few posts, I plan to share some observations and surprises farmers encounter when we dig into what they can do to improve the sustainability of their farms and food production systems.
Land O’ Lakes has been a member of the Field to Market Alliance for Sustainable Agriculture almost since its inception in 2006 (see https://fieldtomarket.org). Field to Market is a broad consortium of companies and organizations including commodity, trade and environmental groups and academic institutions all with an interest in the sustainability science related to food and agricultural systems. Farmers can enter information about their field and farm practices into the “FieldPrint Calculator,” and get back a report that estimates seven different sustainability metrics and a comparison of those metrics to other farm fields in the database. The FieldPrint calculator is becoming an industry standard for documenting improvements in sustainability as farmers adopt new technologies and practices that increase production while reducing the impact of agriculture on the environment.
Farmers who calculate their sustainability “FieldPrint” usually have lots of questions about their results and what they can do to improve their score. Most farmers are surprised by the strong connection between nitrogen use efficiency and the greenhouse gas emission metric. At first glance, one would think that farming produces greenhouse gasses largely due to the fuel used in the tractors, combines and trucks needed to produce and dry the crop. Actually, the overall impact of fuel used in the field usually has a relatively small impact on greenhouse gas production on most farms, the real culprit is usually fertilizer use efficiency. The production and transportation of fertilizers requires a huge amount of energy. Natural gas is used as both an energy source and as an ingredient in the Haber-Bosch process of turning inert N2 gas from the atmosphere into ammonia fertilizer (NH3). Splitting the stable nitrogen-to-nitrogen bonds (N2 makes up about 78% of the air we breathe) requires lots of energy.
Greenhouse gases like carbon dioxide and methane are given off during the production of nitrogen fertilizer, but a more impactful gas can be emitted after the fertilizer is applied to soil. Nitrous oxide (N20) is up to 300 time more active as a greenhouse gas than carbon dioxide (C02) and large quantities of nitrogen can be lost as N20 from fertilized soils that receive more rain than the crop can use.
The challenge for farmers is that they can’t control the amount of rainfall on their fields; they need to make sure there is sufficient nitrogen available to the crop during critical growth stages, but they can also be vulnerable to periods of excess rainfall. Farmers have access to new tools, technologies and products that can help improve nitrogen use efficiency which improves sustainability of their systems. This is not only good for their bottom line, it is also good for the environment. The more we can understand the challenges of sustainable crop production, the better we can help farmers continue to find ways to improve production while reducing impacts on the environment.