Multi-scale Investigation of Winter Runoff and Nutrient Loss Processes in Actively Managed Dairy Agroecosystems

Agricultural nutrient management is an important area of research and policy development due to water quality degradation by nitrogen (N) and phosphorus (P). Manure application to fields without incorporation is a significant source of N and P loss in runoff. Winter application of dairy manure, which is commonly practiced, is risky given frequent occurrence of runoff from snowmelt and rain-on-snow events. Many states restrict winter spreading of dairy manure, but little process-oriented research of winter runoff and manure nutrient loss has been conducted to support restrictions. Our project will investigate and improve the understanding and modeling of biochemical and physical processes controlling frozen-soil and snowmelt infiltration, runoff, and nutrient loss from soil and applied manure for actively managed dairy systems. Our objectives are to: i) conduct multi-scale experiments to investigate processes controlling winter runoff and nutrient loss from soil and manure; ii) develop novel model routines for winter manure runoff that can be incorporated into process-based, field and watershed-scale models; and iii) use runoff monitoring data to evaluate new model routines. Results will be novel because there is little to no process-level research of N and P loss in runoff from winter-applied dairy manure. Results will inform policy, guidelines, and prediction tools in northern-tier U.S. states where winter manure application is practiced. Better prediction tools that assess N and P loss from agroecosystems and evaluate if new practices and technologies can reduce that loss will help improve U.S. agricultural sustainability by enhancing environmental quality and agricultural economic viability.