Surface application of manure on no-till farms can exacerbate P losses in runoff, contributing to the eutrophication of surface waters. We monitored 12 400-m 2 field plots over 4 yr to compare P losses in surface runoff and lateral subsurface flow with shallow disk injection and broadcast application of dairy manure. Given the substantial variability in annual P losses, as well as a gradual, annual buildup of residual soil test P, significant differences in runoff P losses were detected in only 1 of 4 yr: in 2014, total P losses in runoff were 68% greater from broadcast manure plots than injected manure plots. Dissolved and particulate P were roughly even in their contribution to runoff. Even so, there were significant relationships between annual dissolved P losses and P in the soil surface, which pointed to soils as a regular source of P in runoff. Overall, results confirm the potential for injection to reduce P loss in runoff relative to broadcast application, but because in a few sampling dates injection resulted in greater losses, this study also highlights the importance of assessing mitigation benefits of manure application practices over longer timeframes.
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Water Science and Technology
- Waste Management and Disposal
- Management, Monitoring, Policy and Law