FROSTBURG, MD. — A groundbreaking study by researchers at the University of Maryland Center for Environmental Science published in Nature Food demonstrates that livestock manure represents a largely underused domestic resource for improving agricultural resilience.
Their paper, "A framework for estimating manure nitrogen balance and recycling potential for current and future conditions in the USA," develops a novel framework to evaluate current low rates of manure recycling and identify opportunities to better identify opportunities to better capture and redistribute the substantial nitrogen resources already present in U.S. livestock systems. By calculating the "nutrient gap" where manure is produced and where crops are grown, the study offers a strategic roadmap for a more self-reliant and integrated American food system.
“U.S. farmers already face high costs for synthetic fertilizers, and these prices remain vulnerable to fluctuations driven by global energy markets and international supply chains. Recent geopolitical conflicts further contribute to market volatility and increase prices of fertilizer and energy domestically,” University of Maryland Center for Environmental Science (UMCES) PhD Candidate Yanyu Wang said. “Our research shows that current low rates of manure recycling miss major opportunities to make use of nutrients that already exist within our agricultural system. With better strategies to recover, redistribute, and use these resources more efficiently, we can sustain crop production while reducing reliance on external inputs.”
A Strategic Resource, Not a Waste Product
Managing nitrogen in manure can pose environmental challenges, but it’s also a valuable agricultural input. However, because livestock and crop production are often spatially separated, large amounts of manure nitrogen are either underutilized or overapplied in livestock-dominated regions, leading to significant losses to the environment.
The study quantifies the potential for manure to substitute a portion of synthetic fertilizer use by improving manure recovery and crop nitrogen use efficiency. The framework provides a systematic assessment of manure recycling potential based on the current spatial distribution of livestock and crop production, identifying mismatches between manure supply and crop demand. It also highlights opportunities to enhance manure recovery through technological advancements, socioeconomic changes, and better coupling of livestock and crop systems, offering a practical pathway to improve nutrient management and strengthen the stability of U.S. agricultural systems.
Key Findings Include:
- The Nutrient Gap:
The U.S. currently faces a manure nitrogen deficit, meaning that crop demand is largely met by synthetic fertilizers rather than recycled nutrients already available within the system. - Manure Recovery Potential:
Expanding the use of existing manure management technologies could reduce this deficit by 5%, while developing and applying new technologies and relevant policy changes could enable an additional 21% reduction. - Crop Efficiency Gains:
Improving crop nitrogen use efficiency alone could reduce the deficit by 27%, emphasizing the critical role of improved crop management in narrowing this gap. - Phosphorus Constraints on Manure Recycling Potential:
Manure typically has a low N:P ratio, applying it based solely on crop nitrogen needs can lead to phosphorus overapplication. This highlights the complexity of nutrient management and the need for new phosphorus removal technologies. - Varying Regional Priorities:
County-level analysis reveals distinct regional priorities in improving manure recycling, from managing excess manure, to areas with potential to reach balance, to regions facing persistent nutrient deficits.
