An assessment of in-field nutrient best management practices for agricultural crop systems with subsurface drainage

Land drainage to support agricultural production can be traced back thousands of years to the ancient civilization of Mesopotamia along the banks of the Euphrates and Tigris. A ubiquitous drainage need in the Great Lakes region and parts of the Mississippi Basin is subsurface drainage (generally called tile drainage) to remove excess water from fields and improve trafficability. However, it has long been recognized that tile drainage is a main contributor of nitrate-nitrogen (NO3-N) to water resources in these regions (Kladivko et al. 2004), and more recently studies have shown that tile drainage exports large amounts of phosphorus (P) (King et al. 2015). Nitrogen discharges from subsurface drainage systems are a common contributor to hypoxic zones in saltwater bodies, and dissolved P discharges are the primary cause of harmful algal blooms in freshwater bodies.