New Publication: A framework for estimating manure nitrogen balance
A new study was published today in Nature Food by PhD candidate Yanyu Wang and co-authors Xin Zhang, Sheri Spiegal and Eric Davidson!
In “A framework for estimating manure nitrogen balance and recycling potential for current and future conditions in the USA,” the authorship team presents a transparent framework for evaluating manure nitrogen (N) recycling potential across the United States. The work compares methods from six previous studies to understand how different assumptions about manure recovery and crop nutrient demand shape estimates of manure recycling potential.
Key findings:
- The current manure N balance in the U.S. is -13.3 ± 1.1 Tg yr-1, reflecting large crop demand currently met with synthetic fertilizer.
- Greater adoption of current manure management technologies could decrease this deficit by 5%, while future technologies could enable an additional 21% reduction.
- Improved crop N efficiency could also decrease the deficit by 27%.
- Phosphorus (P) constraints matter, too! To avoid P overapplication, 33–36% of recoverable manure nitrogen would need to be reduced.
- Ultimately, applying this framework at county level demonstrates variable regional opportunities to improve manure recycling.
Coincidentally, this paper comes online at a time when concern is growing about rising energy and fertilizer prices. The analysis presented here offers a tool to reconsider how locally and regionally available nutrient resources—such as manure—can be better utilized. Recycling manure not only reduces waste to the environment, but can also make agricultural production less dependent on synthetic fertilizer inputs and more resilient to global supply disruptions.
Looking ahead:
Realizing this potential will require addressing technological, logistical, and socioeconomic barriers to manure recycling. Future priorities include…
- More spatially and temporally robust farm surveys to improve manure application estimates
- Greater transparency and harmonization in nutrient accounting methods
- Expanded use of remote sensing to track manure spreading and livestock systems (e.g., CAFOs)
- Improved soil phosphorus monitoring to prevent accumulation
- Disaggregation of manure handling into collection, storage, treatment, and transport stages to identify bottlenecks
- Evaluating new pathways such as anaerobic digestion, manure transport, and alternative organic nutrient sources
Improving nutrient circularity will likely be an important component of building more resilient and sustainable food systems.