Load-discharge relationships reveal the efficacy of manure application practices on sediment and phosphorus loss from agricultural fields

Authors: MILLER, MELISSA - Pennsylvania State University; GALL, HEATHER - Pennsylvania State University; Buda, Anthony; Saporito, Louis - Lou; Veith, Tameria - Tamie; WHITE, CHARLES - Pennsylvania State University; Williams, Chilton; BRASIER, KATHRYN - Pennsylvania State University; Kleinman, Peter; WATSON, JOHN - Pennsylvania State University

Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2018
Publication Date: 11/17/2018
Citation: Miller, M.D., Gall, H.E., Buda, A.R., Saporito, L.S., Veith, T.L., White, C.M., Williams, C.F., Brasier, K.J., Kleinman, P.J., Watson, J.E. 2018. Load-discharge relationships reveal the efficacy of manure application practices on sediment and phosphorus loss from agricultural fields. Agriculture Ecosystems and the Environment. 272:19-28. https://doi.org/10.1016/j.agee.2018.11.001.
DOI: https://doi.org/10.1016/j.agee.2018.11.001

Interpretive Summary: Understanding linkages between landscape hydrology and field management is central to reducing sediment and phosphorus losses from agriculture. In this study, we evaluated the effects of shallow-disk manure injection and surface manure broadcasting on phosphorus and sediment loads in runoff. Results showed that shallow-disk manure injection lowered dissolved and total phosphorus losses relative to broadcasting, while sediment and particulate phosphorus losses were unaltered by manure application method. Findings highlight the potential of shallow-disk manure injection to reduce manure phosphorus losses in runoff.

Technical Abstract: Eutrophication and sedimentation are pervasive challenges in the Chesapeake Bay Watershed. Shallow-disk manure injection has been promoted to mitigate phosphorus (P) losses in runoff while largely maintaining the water quality benefits of no-till, including reducing particulate P and sediment losses. However, field studies seeking to quantify the effectiveness of shallow-disk injection as a P mitigation strategy are constrained by hydrologic variability across spatial and temporal scales. In this study, overland and subsurface flow from twelve plots in central Pennsylvania (PA) were measured and sampled for all P constituents and total solids (TS) from January 2013 to May 2017. We regressed loads of total P (TP), dissolved P (DP), particulate P (PP), and TS against flow depths to evaluate how P and TS losses changed with increasing flow. The results revealed dilution of all P constituents and near-chemostatic behavior (little change in concentration with change in flow) for TS for both application methods. Shallow-disk injection was found to be more effective than broadcasting in promoting dilution of DP, and to a lesser extent, TP. In contrast, the broadcast plots showed stronger dilution patterns than did the injection plots for PP, and there was no difference between application methods for TS. Variability among plots within each manure application practice was largely dependent on relative contributions of overland and subsurface flow due to increased dilution of P by subsurface flow. Overall, shallow-disk injection appears to be an effective practice to reduce DP and TP losses without negating the erosion-reducing benefits of no-till.