Reducing national water degradation: Development and application of a manureshed-identification framework

Authors: HAGUE, MD HAMIDUL - Pennsylvania State University; ANSARI, ABOLFAZL - Pennsylvania State University; Veith, Tameria; White, Michael; COSTELLO, CHRISTINE - Pennsylvania State University; Spiegal, Sheri; Kleinman, Peter; Arnold, Jeffrey; CIBIN, RAJ - Pennsylvania State University

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2025
Publication Date: 6/1/2025
Citation: Hague, M., Ansari, A.H., Veith, T.L., White, M.J., Costello, C., Spiegal, S.A., Kleinman, P.J., Arnold, J.G., Cibin, R. 2025. Reducing national water degradation: Development and application of a manureshed-identification framework. Agricultural Systems. 227. Article 104349. https://doi.org/10.1016/j.agsy.2025.104349.
DOI: https://doi.org/10.1016/j.agsy.2025.104349

Interpretive Summary: The manureshed concept aims to correct nutrient imbalances in areas with intensive livestock production by redistributing excess manure nutrients to fields that need it. This study created a method to evaluate this strategy by analyzing manure production and crop needs at the county level and proposed transport strategies based on distance. The method was tested using the National Agroecosystems Model and the Soil Water Assessment Tool in Georgia's Oconee River Watershed with different manure application scenarios. The analysis found that most counties could balance their surplus manure by transporting to only a few neighboring counties. However, while this approach reduced nutrient overload in areas with excess manure, it slightly increased nutrient levels in receiving areas.

Technical Abstract: The manureshed concept aims to minimize the nutrient imbalance in livestock-intensive agricultural systems by transporting and recycling surplus manure nutrients to agricultural fields with nutrient demands. The impacts of implementing manureshed-based manure management on soil nutrient dynamics and water quality across the continental U.S. (CONUS) needs to be further investigated. The current study aimed to develop a framework to evaluate the impacts of manureshed-based nutrient management in the CONUS. The study did a county-scale manure balancing and delineated manuresheds in the CONUS considering crop nitrogen (N-based) and phosphorus (P-based) demand-based manure application and different types of manure (wet vs. dry) considering their transportation potential. Towards evaluating the impacts of manureshed-based manure management, the National Agroecosystems Model (NAM) model developed using the Soil Water Assessment Tool (SWAT+) was tested in the Oconee River Watershed, Georgia, under different manure application scenarios. The analysis identified four major manuresheds in CONUS using P-based and N-based balancing strategies. Nearly 78% of the wet manure surplus counties (152 counties) required only two neighboring counties to balance excess wet manure P, and about 77% of dry manure surplus counties (428 counties) required only three neighboring counties to balance excess dry manure P. The SWAT+ model simulations of the Upper and Lower Oconee watersheds from NAM showed P-Balanced manureshed-based manure management could reduce organic phosphorus and organic nitrogen loading by 29 and 5% in the manure surplus watershed (Upper Oconee), respectively. However, nutrient loadings increased slightly at the outlet of a manure sink watershed (lower Oconee). The manure balancing and modeling study indicated the intricacies of implementing manureshed-based manure management; the water quality impacts of manureshed-based manure management could vary significantly in source and sink regions and for different nutrient species.