Amid the wind and rain of Midwestern April, the Farm Bill faithful may detect stirrings of a possible start to the long, difficult reauthorization process (Clayton, April 16, 2024; Hagstrom, April 17, 2024; Baethge, April 17, 2024; Abbott, April 16, 2024; Downs, April 8, 2024). Alexander Pope famously wrote that “Hope springs eternal in the human breast” and the line continues to resonate (Pope, 1732; Matteo, March 26, 2022).
The challenges inherent in soil erosion seem also to spring eternal and this article continues that discussion by incorporating an exploration of the research on nitrogen losses, seeking to further build risk-based perspectives (farmdoc daily, March 14, 2024; March 21, 2024; March 28, 2024; see also, December 7, 2023; January 4, 2024; and January 15, 2024). In the spirit of the season, it may be hoped that applying research to develop a wider, more comprehensive perspective on farm risk—one that incorporates natural resource risks—can inform the development of more effective farm polices.
Background Soil erosion adds risk to farming. It can magnify complications in farm management. It also carries significant cost implications. These realities are supported by a substantial body of research (farmdoc daily, March 14, 2024; March 21, 2024; March 28, 2024). Soil erosion possesses a long history and has menaced many societies, persisting as a perennial complication of farming and the production of food (Dotterweich, 2013; Brevik, 2018; Gibbard and Mead, 2020). Among the many challenges of soil erosion is designing effective policy responses. Soil erosion is a complex menace and the loss of nitrogen from fields helps demonstrate the point. One of the most critical nutrients for plant growth, and a major component of topsoil fertility, nitrogen is exported from farm fields in a different process than soil erosion. The two are connected in important ways, however. Erosion of fertile topsoil, for example, requires applications of nitrogen to compensate. Together, they can drive self-feeding cycles, compounding and complicating the challenges. Additionally, neither constitutes actual loss but rather misplacement or displacement, deposited in waterways or somewhere other than the fields where they are needed for crops.
Summarizing the research on the topic is daunting. Humans have likely doubled the amount of reactive nitrogen that cycles through ecosystems across the planet, a substantial portion of which is not consumed as intended. Organic nitrogen abounds in soils but is not available for plants to consume. Bacteria and other microorganisms produce inorganic, plant-available, nitrogen, while ammonium forms of nitrogen are generally added by fertilizer inputs. Nitrogen fertilizers are subject to rapid nitrification to nitrate, the form of nitrogen favored by plants but also the one most soluble and easily transported such as being leached through the soil with water. Nitrate is especially mobile and susceptible to being leached, a risk that is most prominent early in the season when crop growth and nitrogen uptake is low, but mineralization of nitrogen (especially from fertilizer) is high. The complex system of artificial drainage contributes by quickly moving water from precipitation and snowmelt out of farm fields.
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