Monday, 7 November 2005 - 9:00 AM
63-6

Predicting Runoff P Losses from Turfgrass with Soil Testing.

D. Soldat and A.M. Petrovic. Cornell University, Ithaca, NY 14853

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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