Sustainable Nutrient Management beyond the Farm: Chesapeake Bay Case Study

Crop and animal production in agriculture requires nitrogen (N) and phosphorus (P) application. However, poor management of nutrients from field to fork leads to environmental and social problems. In the Chesapeake Bay watershed, progress has been made toward nutrient reduction goals through improved on-farm management strategies in the past few decades. However, progress brought by advanced on-farm practices is limited, and little attention has been paid to key stakeholders and strategies beyond the farm, which may also play crucial roles in sustainable nutrient management.

To that end, we introduce a novel nutrient management framework, CAFE, to connect nutrient management across the Cropping system, Animal-crop system, Food system, and Ecosystem. This framework can be applied to any region and spatial scale to manage nutrient management gaps across systems. Here we apply CAFE to the Chesapeake Bay watershed as a case study.

We quantified the N and P budgets and use efficiencies (NUEs and PUEs) for four CAFE systems and from county to watershed spatial scales through 1985-2019. We found that for most counties in the watershed (>90%), N and P surpluses (a measure of potential nutrient loss) beyond crop farms are larger than cropland nutrient surpluses, meaning larger potential N and P losses at animal production, food processing and retail, transport, and human consumption. Nutrient waste is a rich nutrient resource for food production, as our study shows that nutrient loss from food and human waste can supply more than 80% of current fertilizer inputs. We also analyzed the relationships between nutrient budget and potential drivers, and identified some drivers with a significant impact on nutrient surplus (e.g., population, land use). These management gaps and socioeconomic drivers identified with the CAFE framework indicate potential solutions to reduce nutrient pollution in the watershed.