Excessive concentrations of P can lead to the deterioration of surface waters through eutrophication. This study was conducted to test the effectiveness of a trench filter system for P removal from runoff and to determine the effect of P fertilizer on P losses in runoff from bermudagrass [Cynodon dactylon L. (Pers.)]. A total of 12 plots on a uniform 5% slope covered with a€?Astroa€? bermudagrass mowed at 38 mm were used to collect pre- and postfiltered runoff from 14 natural or simulated precipitation events that occurred from March through September 2012. Runoff filtered by steel slag contained from 14.2 to 49.2% lower dissolved P concentrations than runoff filtered through an inert gravel control. The P concentrations in runoff from fertilized plots were always greater than unfertilized plots. The difference between P concentrations from the fertilized and unfertilized treatments tended to decline with each runoff event from 13.1 mg La€“1 in an initial event after fertilization to 1.6 mg La€“1, 133 d and nine runoff events later. Trench filter systems could be used to remove a portion of the P in runoff from turfgrass areas.
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