Phosphorus Doesn't Move Through Sub-Surface Tile, Right?.

Conventional wisdom suggests that phosphorus does not leach, therefore, many farmers, technical service providers and even experts in the field of water quality believe that P losses through subsurface tile are insufficient to induce water quality problems. Long-term water quality monitoring of the Maumee River indicates that 1.2 kg P/ha have been reported in recent years, which correspond with massive Harmful Algal Blooms (HABs). In the St. Joseph River watershed, one of the primary tributaries to the Maumee River, the National Soil Erosion Research Laboratory has been monitoring surface and subsurface water quality from four fields since 2007. Results from this work show that P losses from surface or subsurface pathways vary widely, but approximately 44% of P loading from these fields has occurred through the subsurface tile.  From these fields, mean surface loading of P was approximately 0.86 kg/ha/yr while mean loading through subsurface tile was approximately 0.71 kg/ha/yr.  Phosphorus loading from subsurface tile is not the only contributor to P losses in the Western Lake Erie Basin, however, we should not discount the importance of P loading through subsurface pathways. A fine balancing act exists though, as without subsurface drainage, most of this area would be unsuitable for agricultural production, and it is, therefore, essential that the scientific community find methods to minimize P loading through both surface as well as subsurface pathways.