Phosphorus (P) loss via runoff from agricultural fields has been identified as an important contributor to freshwater eutrophication. However, eutrophication is also evident in many non-agricultural watersheds. Managed turfgrass areas can constitute a significant portion of these watersheds, and therefore runoff P losses from turfgrass are of interest. This study was conducted to examine the relationship between P in runoff from turfgrass and Mehlich 3, Morgan, and 0.01 M CaCl2 extractable soil P. The effect of sampling depth was also examined. A second objective was to identify a common environmental threshold for New York and areas with similar soils above which P losses in runoff become unacceptable. A miniature rainfall simulator was used to generate runoff from turfgrass on six different soil types around NY exhibiting a wide range of soil P levels. At each site sod was stripped and runoff also generated from bare soil. The results of the study suggest that P in runoff is predicted better by a 0-2 or 0-5 cm sample than a 0-15 cm sample. Also, the unconventional 0.01 M CaCl2 extractant did not predict runoff P losses any better than the common agronomic extractants. Soil test P predicted runoff P at all six sites for bare soil plots, but runoff P was predicted by soil test P by 4 of 6 sites for turfgrass plots. Comparison of runoff from turfgrass and from bare soil on plots with similar soil P levels indicates that at low P levels (<5 mg P kg-1, Morgan 5cm) P concentrations are higher in runoff from turfgrass than bare soil, presumably due to plant contributions of P. While at high levels of soil P (>10 mg P kg-1, Morgan 5cm) P concentrations in runoff are lower from turfgrass than from bare soil.
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