Agricultural phosphorus (P) loss has been linked to the eutrophication of surface water bodies throughout the world. As a result, minimizing offsite P transport has become a priority in many rural watersheds. In the US Midwest and other subsurface tile-drained regions, there is a critical need to identify nutrient management practices that decrease P loss in both surface and subsurface discharge. An edge-of-field (EOF) network monitoring 38 agricultural fields was established in northwest Ohio, United States, to quantify the impacts of prevailing and novel crop production and conservation management practices on surface and subsurface P concentrations and loads. In this study, we evaluate nutrient management practices across these fields with varying characteristics in order to identify a suite of management practices within the 4R nutrient management framework (right source, right rate, right time, and right place) that reduce agricultural P loss in artificially drained landscapes. EOF monitoring data indicate that applying organic fertilizers at P-based rates, soil testing and following recommended application rates, avoiding fertilizer application during wet periods of the year (e.g., winter and early spring) and prior to large precipitation events, and placing fertilizer below the surface are all practices that result in decreased P loss. Findings also highlight the importance of field hydrology on surface and subsurface P transport and suggest that water management practices may also be effective at decreasing P loss. While the effectiveness of the nutrient management practices evaluated in this study will likely vary across fields with different characteristics, implementation of these practices should be considered a directionally correct (i.e., will reduce nutrient loss) approach for addressing excess P loss from artificially drained landscapes.
Bibliographical noteFunding Information:
The authors would like to thank the landowners of the study sites who provided access to the fields and management data; Jedediah Stinner, Katie Rumora, Sara Henderson, Marie Pollock, and Phil Levison (hydrologic technicians, USDA Agricultural Research Service [ARS], Columbus, Ohio) for help in data collection and site maintenance; and Eric Fischer (laboratory chemist, USDA ARS, Columbus, Ohio) for analytical expertise.The authors would like to acknowledge the continued support of The Ohio State University in hosting the USDA ARS Soil Drainage Research Unit and providing academic access to faculty resources, libraries, and students. Funding for this project was provided in part by several sources including: The 4R Research Fund (IPNI-2014-USA-4RN09); US Environmental Protection Agency (USEPA) (DW-12-92342501-0); Conservation Innovation Grants (The Ohio State University – 69-3A75-12-231; Heidelberg University – 69-3A75-13-216); Ohio Corn and Wheat Growers Association; Ohio Soybean Association; USDA Natural Resources Conservation Service (NRCS) Mississippi River Basin Initiative;The Nature Conservancy; NRCS Cooperative Conservation Partnership Initiative; and USDA Conservation Effects Assessment Project.
- Algal bloom
- Lake Erie
- Tile drainage
- Water quality