Managing Acute Phosphorus Loss with Fertilizer Source and Placement: Proof of Concept

Surface water eutrophication is a pervasive global problem, with P losses from agriculture often identified as a significant contributor. This study was conducted to evaluate the implications of fertilizer source and placement on soluble P (SP) losses in runoff. Using the National P Runoff Project protocol, SP losses in runoff from eight P fertilizers broadcast on the soil surface and three P fertilizers banded 1 cm below the surface were compared with a nonfertilized control. Results showed that 16 to 19% of the surface-applied inorganic P fertilizers was lost in one rainstorm, except for liquid polyphosphate, which lost less than 0.2% of the applied P. Banding monoammonium phosphate and poultry litter below the surface decreased SP loading by 98 and 84%, respectively. These results indicate that critical examination of current fertilizer management may be needed to diminish eutrophication while ensuring sufficient P for crop uptake.