Nutrient loss from agricultural systems employing ecological approaches

Background/Question/Methods

Substantially reducing nutrient losses from agricultural systems will require a re-envisioning of agricultural landscapes rather than a re-tooling of current practices. Technology-driven approaches to reducing nitrogen (N) losses, which focus on synthetic N fertilizer management, have consumed the majority of research dollars over the past several decades, yet nutrient losses to surface waters have continued to increase in most major agricultural watersheds in the U.S. We will estimate the relative potential of a gradient of approaches that vary in the degree of systemic change required to reduce agricultural nutrient losses using evidence from literature reviews, university cropping systems experiments, and on-farm research.

Results/Conclusions   

In the near-term and at field scales, ecologically-based nutrient management that relies primarily on plant and microbially-mediated biogeochemical processes could substantially reduce nutrient losses while maintaining crop productivity.  At one end of the gradient, integrating non-legume cover crops into synthetic fertilizer-based systems has the potential to reduce N losses following corn by 65 to 80%. Re-coupling of carbon and N cycles through practices such as the use of legume N sources and diversified crop rotations has the potential to reduce N losses by 30 to 40%.  In the long-term and at larger scales, we will challenge the assumption that current agricultural systems and institutional arrangements are immutable. Addressing the interdependent factors of a corn and soybean dominated landscape, concentrated livestock production systems, and human consumption patterns may offer the greatest opportunities and challenges to reducing nutrient losses.  For example, eating lower on the food chain in the U.S. could reduce land and fertilizer demands by 50%. Substituting perennial plant species for annuals could reduce N losses by more than 90%. Promising research and grassroots movements supporting the development of these alternatives are growing in response to global food, energy and climate crises. Such systemic solutions require an integrated approach to understanding the complex dynamics of socioecological systems and would have cascading benefits for multiple ecosystem services impacted by food production.